Zhi-Xun Shen

All Publications

• Local probe of bulk and edge states in a fractional Chern insulator. Nature Ji, Z., Park, H., Barber, M. E., Hu, C., Watanabe, K., Taniguchi, T., Chu, J. H., Xu, X., Shen, Z. X. 2024; 635 (8039): 578-583

  Abstract

  The fractional quantum Hall effect is a key example of topological quantum many-body phenomena, arising from the interplay between strong electron correlation, topological order and time-reversal symmetry breaking. Recently, a lattice analogue of the fractional quantum Hall effect at zero magnetic field has been observed, confirming the existence of a zero-field fractional Chern insulator (FCI). Despite this, the bulk-edge correspondence-a hallmark of a FCI featuring an insulating bulk with conductive edges-has not been directly observed. In fact, this correspondence has not been visualized in any system for fractional states owing to experimental challenges. Here we report the imaging of FCI edge states in twisted MoTe2 (t-MoTe2) using microwave impedance microscopy1. By tuning the carrier density, we observe the system evolving between metallic and FCI states, the latter of which exhibits insulating bulk and conductive edges, as expected from the bulk-boundary correspondence. Further analysis suggests the composite nature of the FCI edge states. We also observe the evolution of edge states across the topological phase transition as a function of interlayer electric field and reveal exciting prospects of neighbouring domains with different fractional orders. These findings pave the way for research into topologically protected one-dimensional interfaces between various anyonic states at zero magnetic field, such as gapped one-dimensional symmetry-protected phases with non-zero topological entanglement entropy, Halperin-Laughlin interfaces and the creation of non-abelian anyons.

  View details for DOI 10.1038/s41586-024-08092-7

  View details for PubMedID 39567787

  View details for PubMedCentralID 11464376

• Planar Thermal Hall Effect from Phonons in Cuprates PHYSICAL REVIEW X Chen, L., Le Roux, L., Grissonnanche, G., Boulanger, M., Theriault, S., Liang, R., Bonn, D. A., Hardy, W. N., Pyon, S., Takayama, T., Takagi, H., Xu, K., Shen, Z., Taillefer, L. 2024; 14 (4)

  View details for DOI 10.1103/PhysRevX.14.041011

  View details for Web of Science ID 001335552100001

• Anomalous normal-state gap in an electron-doped cuprate. Science (New York, N.Y.) Xu, K. J., He, J., Chen, S. D., He, Y., Abadi, S. N., Rotundu, C. R., Lee, Y. S., Lu, D. H., Guo, Q., Tjernberg, O., Devereaux, T. P., Lee, D. H., Hashimoto, M., Shen, Z. X. 2024; 385 (6710): 796-800

  Abstract

  In the underdoped n-type cuprate Nd2-xCexCuO4, long-range antiferromagnetic order reconstructs the Fermi surface, resulting in a putative antiferromagnetic metal with small Fermi pockets. Using angle-resolved photoemission spectroscopy, we observe an anomalous energy gap, an order of magnitude smaller than the antiferromagnetic gap, in a wide portion of the underdoped regime and smoothly connecting to the superconducting gap at optimal doping. After considering all the known ordering tendencies in tandem with the phase diagram, we hypothesize that the normal-state gap in the underdoped n-type cuprates originates from Cooper pairing. The high temperature scale of the normal-state gap raises the prospect of engineering higher transition temperatures in the n-type cuprates comparable to those of the p-type cuprates.

  View details for DOI 10.1126/science.adk4792

  View details for PubMedID 39146411

• Band structure of Bi surfaces formed on Bi2Se3 upon exposure to air PHYSICAL REVIEW MATERIALS Gauthier, A., Sobota, J. A., Gauthier, N., Rotundu, C. R., Shen, Z., Kirchmann, P. S. 2024; 8 (5)

  View details for DOI 10.1103/PhysRevMaterials.8.054201

  View details for Web of Science ID 001231926400007

• Controlling structure and interfacial interaction of monolayer TaSe2 on bilayer graphene. Nano convergence Lee, H., Im, H., Choi, B. K., Park, K., Chen, Y., Ruan, W., Zhong, Y., Lee, J. E., Ryu, H., Crommie, M. F., Shen, Z. X., Hwang, C., Mo, S. K., Hwang, J. 2024; 11 (1): 14

  Abstract

  Tunability of interfacial effects between two-dimensional (2D) crystals is crucial not only for understanding the intrinsic properties of each system, but also for designing electronic devices based on ultra-thin heterostructures. A prerequisite of such heterostructure engineering is the availability of 2D crystals with different degrees of interfacial interactions. In this work, we report a controlled epitaxial growth of monolayer TaSe2 with different structural phases, 1H and 1 T, on a bilayer graphene (BLG) substrate using molecular beam epitaxy, and its impact on the electronic properties of the heterostructures using angle-resolved photoemission spectroscopy. 1H-TaSe2 exhibits significant charge transfer and band hybridization at the interface, whereas 1 T-TaSe2 shows weak interactions with the substrate. The distinct interfacial interactions are attributed to the dual effects from the differences of the work functions as well as the relative interlayer distance between TaSe2 films and BLG substrate. The method demonstrated here provides a viable route towards interface engineering in a variety of transition-metal dichalcogenides that can be applied to future nano-devices with designed electronic properties.

  View details for DOI 10.1186/s40580-024-00422-9

  View details for PubMedID 38622355

  View details for PubMedCentralID PMC11018566

• Beyond Conventional Charge Density Wave for Strongly Enhanced Two-dimensional Superconductivity in 1H-TaS2Superlattices. Advanced materials (Deerfield Beach, Fla.) Li, Z., Lyu, P., Chen, Z., Guan, D., Yu, S., Zhao, J., Huang, P., Zhou, X., Qiu, Z., Fang, H., Hashimoto, M., Lu, D., Song, F., Loh, K. P., Zheng, Y., Shen, Z., Novoselov, K. S., Lu, J. 2024: e2312341

  Abstract

  Noncentrosymmetric transition metal dichalcogenide (TMD) monolayers offer a fertile platform for exploring unconventional Ising superconductivity (SC) and charge density waves (CDWs). However, the vulnerability of isolated monolayers to structural disorder and environmental oxidation often degrade their electronic coherence. Herein, we report an alternative approach for fabricating stable and intrinsic monolayers of 1H-TaS2 sandwiched between SnS blocks in a (SnS)1.15TaS2 van der Waals (vdW) superlattice. The SnS block layers not only decouple individual 1H-TaS2 sublayers to endow them with monolayer-like electronic characteristics, but also protect the 1H-TaS2 layers from electronic degradation. The results reveal the characteristic 3 * 3 CDW order in 1H-TaS2 sublayers associated with electronic rearrangement in the low-lying S p band, which uncovers a previously undiscovered CDW mechanism rather than the conventional Fermi surface-related framework. Additionally, the (SnS)1.15TaS2 superlattice exhibits a strongly enhanced Ising-like SC with a layer-independent Tc of approximately 3.0 K, comparable to that of the isolated monolayer 1H-TaS2 sample, presumably attributed to their monolayer-like characteristics and retained Fermi states. Our results provide new insights into the long-debated CDW order and enhanced SC of monolayer 1H-TaS2, establishing bulk vdW superlattices as promising platforms for investigating exotic collective quantum phases in the two-dimensional limit. This article is protected by copyright. All rights reserved.

  View details for DOI 10.1002/adma.202312341

  View details for PubMedID 38567889

• Unraveling sources of emission heterogeneity in Silicon Vacancy color centers with cryo-cathodoluminescence microscopy. Proceedings of the National Academy of Sciences of the United States of America Angell, D. K., Li, S., Utzat, H., Thurston, M. L., Liu, Y., Dahl, J., Carlson, R., Shen, Z. X., Melosh, N., Sinclair, R., Dionne, J. A. 2024; 121 (14): e2308247121

  Abstract

  Diamond color centers have proven to be versatile quantum emitters and exquisite sensors of stress, temperature, electric and magnetic fields, and biochemical processes. Among color centers, the silicon-vacancy (SiV[Formula: see text]) defect exhibits high brightness, minimal phonon coupling, narrow optical linewidths, and high degrees of photon indistinguishability. Yet the creation of reliable and scalable SiV[Formula: see text]-based color centers has been hampered by heterogeneous emission, theorized to originate from surface imperfections, crystal lattice strain, defect symmetry, or other lattice impurities. Here, we advance high-resolution cryo-electron microscopy combined with cathodoluminescence spectroscopy and 4D scanning transmission electron microscopy (STEM) to elucidate the structural sources of heterogeneity in SiV[Formula: see text] emission from nanodiamond with sub-nanometer-scale resolution. Our diamond nanoparticles are grown directly on TEM membranes from molecular-level seedings, representing the natural formation conditions of color centers in diamond. We show that individual subcrystallites within a single nanodiamond exhibit distinct zero-phonon line (ZPL) energies and differences in brightness that can vary by 0.1 meV in energy and over 70% in brightness. These changes are correlated with the atomic-scale lattice structure. We find that ZPL blue-shifts result from tensile strain, while ZPL red shifts are due to compressive strain. We also find that distinct crystallites host distinct densities of SiV[Formula: see text] emitters and that grain boundaries impact SiV[Formula: see text] emission significantly. Finally, we interrogate nanodiamonds as small as 40 nm in diameter and show that these diamonds exhibit no spatial change to their ZPL energy. Our work provides a foundation for atomic-scale structure-emission correlation, e.g., of single atomic defects in a range of quantum and two-dimensional materials.

  View details for DOI 10.1073/pnas.2308247121

  View details for PubMedID 38551833

• Characterization of Two Fast-Turnaround Dry Dilution Refrigerators for Scanning Probe Microscopy JOURNAL OF LOW TEMPERATURE PHYSICS Barber, M. E., Li, Y., Gibson, J., Yu, J., Jiang, Z., Hu, Y., Ji, Z., Nandi, N., Hoke, J. C., Bishop-Van Horn, L., Arias, G. R., Van Harlingen, D. J., Moler, K. A., Shen, Z., Kou, A., Feldman, B. E. 2024

  View details for DOI 10.1007/s10909-023-03035-4

  View details for Web of Science ID 001190209400002

• Charge density waves in two-dimensional transition metal dichalcogenides. Reports on progress in physics. Physical Society (Great Britain) Hwang, J., Ruan, W., Chen, Y., Tang, S., Crommie, M. F., Shen, Z., Mo, S. 2024

  Abstract

  Charge density wave (CDW) is one of the most ubiquitous electronic orders in quantum materials. While the essential ingredients of CDW order have been extensively studied, a comprehensive microscopic understanding is yet to be reached. Recent research efforts on the CDW phenomena in two-dimensional (2D) materials provide a new pathway toward a deeper understanding of its complexity. This review provides an overview of the CDW orders in 2D with atomically thin transition metal dichalcogenides (TMDCs) as the materials platform. We mainly focus on the electronic structure investigations on the epitaxially grown TMDC samples with angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy as complementary experimental tools. We discuss the possible origins of the 2D CDW, novel quantum states co-existing with them, and exotic types of charge orders that can only be realized in the 2D limit. .

  View details for DOI 10.1088/1361-6633/ad36d3

  View details for PubMedID 38518359

• Evidence for d-wave superconductivity of infinite-layer nickelates from low-energy electrodynamics. Nature materials Cheng, B., Cheng, D., Lee, K., Luo, L., Chen, Z., Lee, Y., Wang, B. Y., Mootz, M., Perakis, I. E., Shen, Z. X., Hwang, H. Y., Wang, J. 2024

  Abstract

  The discovery of superconductivity in infinite-layer nickelates established another category of unconventional superconductors that shares structural and electronic similarities with cuprates. However, key issues of the superconducting pairing symmetry, gap amplitude and superconducting fluctuations are yet to be addressed. Here we utilize static and ultrafast terahertz spectroscopy to address these. We demonstrate that the equilibrium terahertz conductivity and non-equilibrium terahertz responses of an optimally Sr-doped nickelate film (superconducting transition temperature of Tc = 17 K) are in line with the electrodynamics of d-wave superconductivity in the dirty limit. The gap-to-Tc ratio (2Δ/kBTc) is found to be 3.4, indicating that the superconductivity falls in the weak coupling regime. In addition, we observed substantial superconducting fluctuations near Tc that do not extend into the deep normal state as the optimally hole-doped cuprates do. Our results support a d-wave system that closely resembles the electron-doped cuprates.

  View details for DOI 10.1038/s41563-023-01766-z

  View details for PubMedID 38182811

• Probing the edge states of Chern insulators using microwave impedance microscopy PHYSICAL REVIEW B Wang, T., Wu, C., Mogi, M., Kawamura, M., Tokura, Y., Shen, Z., You, Y., Allen, M. T. 2023; 108 (23)

  View details for DOI 10.1103/PhysRevB.108.235432

  View details for Web of Science ID 001145859800004

• Efficient Photonic Integration of Diamond Color Centers and Thin-Film Lithium Niobate ACS PHOTONICS Riedel, D., Lee, H., Herrmann, J. F., Grzesik, J., Ansari, V., Borit, J., Stokowski, H. S., Aghaeimeibodi, S., Lu, H., McQuade, P. J., Melosh, N. A., Shen, Z., Safavi-Naeini, A. H., Vuckovic, J. 2023; 10 (12): 4236-4243

  View details for DOI 10.1021/acsphotonics.3c00992

  View details for Web of Science ID 001128748300001

• Bogoliubov quasiparticle on the gossamer Fermi surface in electron-doped cuprates NATURE PHYSICS Xu, K., Guo, Q., Hashimoto, M., Li, Z., Chen, S., He, J., He, Y., Li, C., Berntsen, M. H., Rotundu, C. R., Lee, Y. S., Devereaux, T. P., Rydh, A., Lu, D., Lee, D., Tjernberg, O., Shen, Z. 2023; 19 (12): 1834-+

  View details for DOI 10.1038/s41567-023-02209-x

  View details for Web of Science ID 001178645300029

• Coherent light control of a metastable hidden state. Science advances Maklar, J., Sarkar, J., Dong, S., Gerasimenko, Y. A., Pincelli, T., Beaulieu, S., Kirchmann, P. S., Sobota, J. A., Yang, S., Leuenberger, D., Moore, R. G., Shen, Z. X., Wolf, M., Mihailovic, D., Ernstorfer, R., Rettig, L. 2023; 9 (47): eadi4661

  Abstract

  Metastable phases present a promising route to expand the functionality of complex materials. Of particular interest are light-induced metastable phases that are inaccessible under equilibrium conditions, as they often host new, emergent properties switchable on ultrafast timescales. However, the processes governing the trajectories to such hidden phases remain largely unexplored. Here, using time- and angle-resolved photoemission spectroscopy, we investigate the ultrafast dynamics of the formation of a hidden quantum state in the layered dichalcogenide 1T-TaS2 upon photoexcitation. Our results reveal the nonthermal character of the transition governed by a collective charge-density-wave excitation. Using a double-pulse excitation of the structural mode, we show vibrational coherent control of the phase-transition efficiency. Our demonstration of exceptional control, switching speed, and stability of the hidden state are key for device applications at the nexus of electronics and photonics.

  View details for DOI 10.1126/sciadv.adi4661

  View details for PubMedID 38000022

• Spin skyrmion gaps as signatures of strong-coupling insulators in magic-angle twisted bilayer graphene. Nature communications Yu, J., Foutty, B. A., Kwan, Y. H., Barber, M. E., Watanabe, K., Taniguchi, T., Shen, Z. X., Parameswaran, S. A., Feldman, B. E. 2023; 14 (1): 6679

  Abstract

  The flat electronic bands in magic-angle twisted bilayer graphene (MATBG) host a variety of correlated insulating ground states, many of which are predicted to support charged excitations with topologically non-trivial spin and/or valley skyrmion textures. However, it has remained challenging to experimentally address their ground state order and excitations, both because some of the proposed states do not couple directly to experimental probes, and because they are highly sensitive to spatial inhomogeneities in real samples. Here, using a scanning single-electron transistor, we observe thermodynamic gaps at even integer moiré filling factors at low magnetic fields. We find evidence of a field-tuned crossover from charged spin skyrmions to bare particle-like excitations, suggesting that the underlying ground state belongs to the manifold of strong-coupling insulators. From the spatial dependence of these states and the chemical potential variation within the flat bands, we infer a link between the stability of the correlated ground states and local twist angle and strain. Our work advances the microscopic understanding of the correlated insulators in MATBG and their unconventional excitations.

  View details for DOI 10.1038/s41467-023-42275-6

  View details for PubMedID 37865663

  View details for PubMedCentralID 8099185

• Angle-resolved pair photoemission theory for correlated electrons PHYSICAL REVIEW B Devereaux, T. P., Claassen, M., Huang, X., Zaletel, M., Moore, J. E., Morr, D., Mahmood, F., Abbamonte, P., Shen, Z. 2023; 108 (6)

  View details for DOI 10.1103/PhysRevB.108.165134

  View details for Web of Science ID 001100593900005

• Development of deflector mode for spin-resolved time-of-flight photoemission spectroscopy. The Review of scientific instruments Han, X., Qu, J., Sakamoto, S., Liu, D., Guan, D., Liu, J., Li, H., Rotundu, C. R., Andresen, N., Jozwiak, C., Hussain, Z., Shen, Z. X., Sobota, J. A. 2023; 94 (10)

  Abstract

  Spin- and angle-resolved photoemission spectroscopy ("spin-ARPES") is a powerful technique for probing the spin degree-of-freedom in materials with nontrivial topology, magnetism, and strong correlations. Spin-ARPES faces severe experimental challenges compared to conventional ARPES attributed to the dramatically lower efficiency of its detection mechanism, making it crucial for instrumentation developments that improve the overall performance of the technique. In this paper, we demonstrate the functionality of our spin-ARPES setup based on time-of-flight spectroscopy and introduce our recent development of an electrostatic deflector mode to map out spin-resolved band structures without sample rotation. We demonstrate the functionality by presenting the spin-resolved spectra of the topological insulator Bi2Te3 and describe in detail the spectrum calibrations based on numerical simulations. By implementing the deflector mode, we minimize the need for sample rotation during measurements, hence improving the overall efficiency of experiments on small or inhomogeneous samples.

  View details for DOI 10.1063/5.0168447

  View details for PubMedID 37850856

• Bogoliubov quasiparticle on the gossamer Fermi surface in electron-doped cuprates NATURE PHYSICS Xu, K., Guo, Q., Hashimoto, M., Li, Z., Chen, S., He, J., He, Y., Li, C., Berntsen, M. H., Rotundu, C. R., Lee, Y. S., Devereaux, T. P., Rydh, A., Lu, D., Lee, D., Tjernberg, O., Shen, Z. 2023

  View details for DOI 10.1038/s41567-023-02209

  View details for Web of Science ID 001071598400003

• Ingredients of strong interactions in cuprates PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS Shen, Z., Devereaux, T. 2023; 613

  View details for DOI 10.1016/j.physc.2023.1354356

  View details for Web of Science ID 001084745200001

• From Stoner to local moment magnetism in atomically thin Cr2Te3. Nature communications Zhong, Y., Peng, C., Huang, H., Guan, D., Hwang, J., Hsu, K. H., Hu, Y., Jia, C., Moritz, B., Lu, D., Lee, J. S., Jia, J. F., Devereaux, T. P., Mo, S. K., Shen, Z. X. 2023; 14 (1): 5340

  Abstract

  The field of two-dimensional (2D) ferromagnetism has been proliferating over the past few years, with ongoing interests in basic science and potential applications in spintronic technology. However, a high-resolution spectroscopic study of the 2D ferromagnet is still lacking due to the small size and air sensitivity of the exfoliated nanoflakes. Here, we report a thickness-dependent ferromagnetism in epitaxially grown Cr2Te3 thin films and investigate the evolution of the underlying electronic structure by synergistic angle-resolved photoemission spectroscopy, scanning tunneling microscopy, x-ray absorption spectroscopy, and first-principle calculations. A conspicuous ferromagnetic transition from Stoner to Heisenberg-type is directly observed in the atomically thin limit, indicating that dimensionality is a powerful tuning knob to manipulate the novel properties of 2D magnetism. Monolayer Cr2Te3 retains robust ferromagnetism, but with a suppressed Curie temperature, due to the drastic drop in the density of states near the Fermi level. Our results establish atomically thin Cr2Te3 as an excellent platform to explore the dual nature of localized and itinerant ferromagnetism in 2D magnets.

  View details for DOI 10.1038/s41467-023-40997-1

  View details for PubMedID 37660171

  View details for PubMedCentralID PMC10475109

• Traces of electron-phonon coupling in one-dimensional cuprates. Nature communications Tang, T., Moritz, B., Peng, C., Shen, Z. X., Devereaux, T. P. 2023; 14 (1): 3129

  Abstract

  The appearance of certain spectral features in one-dimensional (1D) cuprate materials has been attributed to a strong, extended attractive coupling between electrons. Here, using time-dependent density matrix renormalization group methods on a Hubbard-extended Holstein model, we show that extended electron-phonon (e-ph) coupling presents an obvious choice to produce such an attractive interaction that reproduces the observed spectral features and doping dependence seen in angle-resolved photoemission experiments: diminished 3kF spectral weight, prominent spectral intensity of a holon-folding branch, and the correct holon band width. While extended e-ph coupling does not qualitatively alter the ground state of the 1D system compared to the Hubbard model, it quantitatively enhances the long-range superconducting correlations and suppresses spin correlations. Such an extended e-ph interaction may be an important missing ingredient in describing the physics of the structurally similar two-dimensional high-temperature superconducting layered cuprates, which may tip the balance between intertwined orders in favor of uniform d-wave superconductivity.

  View details for DOI 10.1038/s41467-023-38408-6

  View details for PubMedID 37253739

  View details for PubMedCentralID PMC10229634

• Terahertz-Driven Local Dipolar Correlation in a Quantum Paraelectric. Physical review letters Cheng, B., Kramer, P. L., Shen, Z. X., Hoffmann, M. C. 2023; 130 (12): 126902

  Abstract

  Light-induced ferroelectricity in quantum paraelectrics is a new avenue of achieving dynamic stabilization of hidden orders in quantum materials. In this Letter, we explore the possibility of driving a transient ferroelectric phase in the quantum paraelectric KTaO_{3} via intense terahertz excitation of the soft mode. We observe a long-lived relaxation in the terahertz-driven second harmonic generation (SHG) signal that lasts up to 20 ps at 10 K, which may be attributed to light-induced ferroelectricity. Through analyzing the terahertz-induced coherent soft-mode oscillation and finding its hardening with fluence well described by a single-well potential, we demonstrate that intense terahertz pulses up to 500  kV/cm cannot drive a global ferroelectric phase in KTaO_{3}. Instead, we find the unusual long-lived relaxation of the SHG signal comes from a terahertz-driven moderate dipolar correlation between the defect-induced local polar structures. We discuss the impact of our findings on current investigations of the terahertz-induced ferroelectric phase in quantum paraelectrics.

  View details for DOI 10.1103/PhysRevLett.130.126902

  View details for PubMedID 37027861

• Signatures of the exciton gas phase and its condensation in monolayer 1T-ZrTe2. Nature communications Song, Y., Jia, C., Xiong, H., Wang, B., Jiang, Z., Huang, K., Hwang, J., Li, Z., Hwang, C., Liu, Z., Shen, D., Sobota, J. A., Kirchmann, P., Xue, J., Devereaux, T. P., Mo, S. K., Shen, Z. X., Tang, S. 2023; 14 (1): 1116

  Abstract

  The excitonic insulator (EI) is a Bose-Einstein condensation (BEC) of excitons bound by electron-hole interaction in a solid, which could support high-temperature BEC transition. The material realization of EI has been challenged by the difficulty of distinguishing it from a conventional charge density wave (CDW) state. In the BEC limit, the preformed exciton gas phase is a hallmark to distinguish EI from conventional CDW, yet direct experimental evidence has been lacking. Here we report a distinct correlated phase beyond the 2×2 CDW ground state emerging in monolayer 1T-ZrTe2 and its investigation by angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM). The results show novel band- and energy-dependent folding behavior in a two-step process, which is the signatures of an exciton gas phase prior to its condensation into the final CDW state. Our findings provide a versatile two-dimensional platform that allows tuning of the excitonic effect.

  View details for DOI 10.1038/s41467-023-36857-7

  View details for PubMedID 36849499

  View details for PubMedCentralID PMC9971207

• Influence of local symmetry on lattice dynamics coupled to topological surface states PHYSICAL REVIEW B Sobota, J. A., Teitelbaum, S. W., Huang, Y., Querales-Flores, J. D., Power, R., Allen, M., Rotundu, C. R., Bailey, T. P., Uher, C., Henighan, T., Jiang, M., Zhu, D., Chollet, M., Sato, T., Trigo, M., Murray, e. D., Savic, I., Kirchmann, P. S., Fahy, S., Reis, D. A., Shen, Z. 2023; 107 (1)

  View details for DOI 10.1103/PhysRevB.107.014305

  View details for Web of Science ID 000921610800004

• Identification of a characteristic doping for charge order phenomena in Bi-2212 cuprates via RIXS PHYSICAL REVIEW B Lu, H., Hashimoto, M., Chen, S., Ishida, S., Song, D., Eisaki, H., Nag, A., Garcia-Fernandez, M., Arpaia, R., Ghiringhelli, G., Braicovich, L., Zaanen, J., Moritz, B., Kummer, K., Brookes, N. B., Zhou, K., Shen, Z., Devereaux, T. P., Lee, W. 2022; 106 (15)

  View details for DOI 10.1103/PhysRevB.106.155109

  View details for Web of Science ID 000918192100003

• Evidence for a spinon Kondo effect in cobalt atoms on single-layer 1T-TaSe2 NATURE PHYSICS Chen, Y., He, W., Ruan, W., Hwang, J., Tang, S., Lee, R. L., Wu, M., Zhu, T., Zhang, C., Ryu, H., Wang, F., Louie, S. G., Shen, Z., Mo, S., Lee, P. A., Crommie, M. F. 2022

  View details for DOI 10.1038/s41567-022-01751-4

  View details for Web of Science ID 000863144600003

• Differentiated roles of Lifshitz transition on thermodynamics and superconductivity in La2-xSrxCuO4. Proceedings of the National Academy of Sciences of the United States of America Zhong, Y., Chen, Z., Chen, S., Xu, K., Hashimoto, M., He, Y., Uchida, S., Lu, D., Mo, S., Shen, Z. 2022; 119 (32): e2204630119

  Abstract

  The effect of Lifshitz transition on thermodynamics and superconductivity in hole-doped cuprates has been heavily debated but remains an open question. In particular, an observed peak of electronic specific heat is proposed to originate from fluctuations of a putative quantum critical point p* (e.g., the termination of pseudogap at zero temperature), which is close to but distinguishable from the Lifshitz transition in overdoped La-based cuprates where the Fermi surface transforms from hole-like to electron-like. Here we report an in situ angle-resolved photoemission spectroscopy study of three-dimensional Fermi surfaces in La2-xSrxCuO4 thin films (x = 0.06 to 0.35). With accurate kz dispersion quantification, the said Lifshitz transition is determined to happen within a finite range around x = 0.21. Normal state electronic specific heat, calculated from spectroscopy-derived band parameters, reveals a doping-dependent profile with a maximum at x = 0.21 that agrees with previous thermodynamic microcalorimetry measurements. The account of the specific heat maximum by underlying band structures excludes the need for additionally dominant contribution from the quantum fluctuations at p*. A d-wave superconducting gap smoothly across the Lifshitz transition demonstrates the insensitivity of superconductivity to the dramatic density of states enhancement.

  View details for DOI 10.1073/pnas.2204630119

  View details for PubMedID 35914123

• A Novel 19*19 Superstructure in Epitaxially Grown 1T-TaTe2. Advanced materials (Deerfield Beach, Fla.) Hwang, J., Jin, Y., Zhang, C., Zhu, T., Kim, K., Zhong, Y., Lee, J., Shen, Z., Chen, Y., Ruan, W., Ryu, H., Hwang, C., Lee, J., Crommie, M. F., Mo, S., Shen, Z. 2022: e2204579

  Abstract

  The spontaneous formation of electronic orders is a crucial element for understanding complex quantum states and engineering heterostructures in two-dimensional materials. We report a novel 19*19 charge order in few-layer thick 1T-TaTe2 transition metal dichalcogenide films grown by molecular beam epitaxy, which has not been realized. Our photoemission and scanning probe measurements demonstrate that monolayer 1T-TaTe2 exhibits a variety of metastable charge density wave orders, including the 19*19 superstructure, which can be selectively stabilized by controlling the post-growth annealing temperature. Moreover, we find that only the 19*19 order persists in 1T-TaTe2 films thicker than a monolayer, up to 8 layers. Our findings identify the previously unrealized novel electronic order in a much-studied transition metal dichalcogenide and provide a viable route to control it within the epitaxial growth process. This article is protected by copyright. All rights reserved.

  View details for DOI 10.1002/adma.202204579

  View details for PubMedID 35902365

• A broken translational symmetry state in an infinite-layer nickelate NATURE PHYSICS Rossi, M., Osada, M., Choi, J., Agrestini, S., Jost, D., Lee, Y., Lu, H., Wang, B., Lee, K., Nag, A., Chuang, Y., Kuo, C., Lee, S., Moritz, B., Devereaux, T. P., Shen, Z., Lee, J., Zhou, K., Hwang, H. Y., Lee, W. 2022

  View details for DOI 10.1038/s41567-022-01660-6

  View details for Web of Science ID 000829739500004

• Electronic nature of the pseudogap in electron-doped Sr2IrO4 NPJ QUANTUM MATERIALS Peng, S., Lane, C., Hu, Y., Guo, M., Chen, X., Sun, Z., Hashimoto, M., Lu, D., Shen, Z., Wu, T., Chen, X., Markiewicz, R. S., Wang, Y., Bansil, A., Wilson, S. D., He, J. 2022; 7 (1)

  View details for DOI 10.1038/s41535-022-00467-1

  View details for Web of Science ID 000805777800001

• Electronic structure of superconducting nickelates probed by resonant photoemission spectroscopy MATTER Chen, Z., Osada, M., Li, D., Been, E. M., Chen, S., Hashimoto, M., Lu, D., Mo, S., Lee, K., Wang, B., Rodolakis, F., McChesney, J. L., Jia, C., Moritz, B., Devereaux, T. P., Hwang, H. Y., Shen, Z. 2022; 5 (6)

  View details for DOI 10.1016/j.matt.2022.01.020

  View details for Web of Science ID 000810939100001

• Momentum-resolved resonant inelastic soft X-ray scattering (qRIXS) endstation at the ALS JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Chuang, Y., Feng, X., Cruz, A., Hanzel, K., Brown, A., Spucces, A., Frano, A., Lee, W., Kim, J., Chen, Y., Smith, B., Pepper, J. S., Shao, Y., Huang, S., Wray, L., Gullikson, E., Shen, Z., Devereaux, T. P., Tremsin, A., Yang, W., Guo, J., Duarte, R., Hussain, Z. 2022; 257

  View details for DOI 10.1016/j.elspec.2019.146897

  View details for Web of Science ID 000816180900004

• Correlated Hofstadter spectrum and flavour phase diagram in magic-angle twisted bilayer graphene NATURE PHYSICS Yu, J., Foutty, B. A., Han, Z., Barber, M. E., Schattner, Y., Watanabe, K., Taniguchi, T., Phillips, P., Shen, Z., Kivelson, S. A., Feldman, B. E. 2022

  View details for DOI 10.1038/s41567-022-01589-w

  View details for Web of Science ID 000787131300001

• Laser-induced patterning for a diffraction grating using the phase change material of Ge2Sb2Te5 (GST) as a spatial light modulator in X-ray optics: a proof of concept OPTICAL MATERIALS EXPRESS Park, J., Zalden, P., Ng, E., Johnston, S., Fong, S. W., Chang, C., Tassone, C. J., Van Campen, D., Mok, W., Mabuchi, H., Wong, H., Shen, Z., Lindenberg, A. M., Sakdinawat, A. 2022; 12 (4): 1408-1416

  View details for DOI 10.1364/OME.451534

  View details for Web of Science ID 000790447300002

• Thermal Hall conductivity of electron-doped cuprates PHYSICAL REVIEW B Boulanger, M., Grissonnanche, G., Lefrancois, E., Gourgout, A., Xu, K., Shen, Z., Greene, R. L., Taillefer, L. 2022; 105 (11)

  View details for DOI 10.1103/PhysRevB.105.115101

  View details for Web of Science ID 000766641000001

• Large-gap insulating dimer ground state in monolayer IrTe2. Nature communications Hwang, J., Kim, K., Zhang, C., Zhu, T., Herbig, C., Kim, S., Kim, B., Zhong, Y., Salah, M., El-Desoky, M. M., Hwang, C., Shen, Z., Crommie, M. F., Mo, S. 2022; 13 (1): 906

  Abstract

  Monolayers of two-dimensional van der Waals materials exhibit novel electronic phases distinct from their bulk due to the symmetry breaking and reduced screening in the absence of the interlayer coupling. In this work, we combine angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy to demonstrate the emergence of a unique insulating 2 * 1 dimer ground state in monolayer 1T-IrTe2 that has a large band gap in contrast to the metallic bilayer-to-bulk forms of this material. First-principles calculations reveal that phonon and charge instabilities as well as local bond formation collectively enhance and stabilize a charge-ordered ground state. Our findings provide important insights into the subtle balance of interactions having similar energy scales that occurs in the absence of strong interlayer coupling, which offers new opportunities to engineer the properties of 2D monolayers.

  View details for DOI 10.1038/s41467-022-28542-y

  View details for PubMedID 35173153

• Unconventional Hysteretic Transition in a Charge Density Wave. Physical review letters Lv, B. Q., Zong, A., Wu, D., Rozhkov, A. V., Fine, B. V., Chen, S. D., Hashimoto, M., Lu, D. H., Li, M., Huang, Y. B., Ruff, J. P., Walko, D. A., Chen, Z. H., Hwang, I., Su, Y., Shen, X., Wang, X., Han, F., Po, H. C., Wang, Y., Jarillo-Herrero, P., Wang, X., Zhou, H., Sun, C. J., Wen, H., Shen, Z. X., Wang, N. L., Gedik, N. 2022; 128 (3): 036401

  Abstract

  Hysteresis underlies a large number of phase transitions in solids, giving rise to exotic metastable states that are otherwise inaccessible. Here, we report an unconventional hysteretic transition in a quasi-2D material, EuTe_{4}. By combining transport, photoemission, diffraction, and x-ray absorption measurements, we observe that the hysteresis loop has a temperature width of more than 400 K, setting a record among crystalline solids. The transition has an origin distinct from known mechanisms, lying entirely within the incommensurate charge density wave (CDW) phase of EuTe_{4} with no change in the CDW modulation periodicity. We interpret the hysteresis as an unusual switching of the relative CDW phases in different layers, a phenomenon unique to quasi-2D compounds that is not present in either purely 2D or strongly coupled 3D systems. Our findings challenge the established theories on metastable states in density wave systems, pushing the boundary of understanding hysteretic transitions in a broken-symmetry state.

  View details for DOI 10.1103/PhysRevLett.128.036401

  View details for PubMedID 35119886

• Unconventional spectral signature of Tc in a pure d-wave superconductor. Nature Chen, S., Hashimoto, M., He, Y., Song, D., He, J., Li, Y., Ishida, S., Eisaki, H., Zaanen, J., Devereaux, T. P., Lee, D., Lu, D., Shen, Z. 1800; 601 (7894): 562-567

  Abstract

  In conventional superconductors, the phase transition into a zero-resistance and perfectly diamagnetic state is accompanied by a jump in the specific heat and the opening of a spectral gap1. In the high-transition-temperature (high-Tc) cuprates, although the transport, magnetic and thermodynamic signatures of Tc have been known since the 1980s2, the spectroscopic singularity associated with the transition remains unknown. Here we resolve this long-standing puzzle with a high-precision angle-resolved photoemission spectroscopy (ARPES) study on overdoped (Bi,Pb)2Sr2CaCu2O8+delta (Bi2212). We first probe the momentum-resolved electronic specific heat via spectroscopy and reproduce the specific heat peak at Tc, completing the missing link for a holistic description of superconductivity. Then, by studying the full momentum, energy and temperature evolution of the spectra, we reveal that this thermodynamic anomaly arises from the singular growth of in-gap spectral intensity across Tc. Furthermore, we observe that the temperature evolution of in-gap intensity is highly anisotropic in the momentum space, and the gap itself obeys both the d-wave functional form and particle-hole symmetry. These findings support the scenario that the superconducting transition is driven by phase fluctuations. They also serve as an anchor point for understanding the Fermi arc and pseudogap phenomena in underdoped cuprates.

  View details for DOI 10.1038/s41586-021-04251-2

  View details for PubMedID 35082417

• Expanding the momentum field of view in angle-resolved photoemission systems with hemispherical analyzers. The Review of scientific instruments Gauthier, N., Sobota, J. A., Pfau, H., Gauthier, A., Soifer, H., Bachmann, M. D., Fisher, I. R., Shen, Z. X., Kirchmann, P. S. 2021; 92 (12): 123907

  Abstract

  In photoelectron spectroscopy, the measured electron momentum range is intrinsically related to the excitation photon energy. Low photon energies <10 eV are commonly encountered in laser-based photoemission and lead to a momentum range that is smaller than the Brillouin zones of most materials. This can become a limiting factor when studying condensed matter with laser-based photoemission. An additional restriction is introduced by widely used hemispherical analyzers that record only electrons photoemitted in a solid angle set by the aperture size at the analyzer entrance. Here, we present an upgrade to increase the effective solid angle that is measured with a hemispherical analyzer. We achieve this by accelerating the photoelectrons toward the analyzer with an electric field that is generated by a bias voltage on the sample. Our experimental geometry is comparable to a parallel plate capacitor, and therefore, we approximate the electric field to be uniform along the photoelectron trajectory. With this assumption, we developed an analytic, parameter-free model that relates the measured angles to the electron momenta in the solid and verify its validity by comparing with experimental results on the charge density wave material TbTe3. By providing a larger field of view in momentum space, our approach using a bias potential considerably expands the flexibility of laser-based photoemission setups.

  View details for DOI 10.1063/5.0053479

  View details for PubMedID 34972440

• Expanding the momentum field of view in angle-resolved photoemission systems with hemispherical analyzers REVIEW OF SCIENTIFIC INSTRUMENTS Gauthier, N., Sobota, J. A., Pfau, H., Gauthier, A., Soifer, H., Bachmann, M. D., Fisher, I. R., Shen, Z., Kirchmann, P. S. 2021; 92 (12)

  View details for DOI 10.1063/5.0053479

  View details for Web of Science ID 000731435700002

• Microwave impedance microscopy and its application to quantum materials NATURE REVIEWS PHYSICS Barber, M. E., Ma, E., Shen, Z. 2021

  View details for DOI 10.1038/s42254-021-00386-3

  View details for Web of Science ID 000722126700001

• Phonon-Mediated Long-Range Attractive Interaction in One-Dimensional Cuprates PHYSICAL REVIEW LETTERS Wang, Y., Chen, Z., Shi, T., Moritz, B., Shen, Z., Devereaux, T. P. 2021; 127 (19): 197003

  Abstract

  Establishing a minimal microscopic model for cuprates is a key step towards the elucidation of a high-T_{c} mechanism. By a quantitative comparison with a recent in situ angle-resolved photoemission spectroscopy measurement in doped 1D cuprate chains, our simulation identifies a crucial contribution from long-range electron-phonon coupling beyond standard Hubbard models. Using reasonable ranges of coupling strengths and phonon energies, we obtain a strong attractive interaction between neighboring electrons, whose strength is comparable to experimental observations. Nonlocal couplings play a significant role in the mediation of neighboring interactions. Considering the structural and chemical similarity between 1D and 2D cuprate materials, this minimal model with long-range electron-phonon coupling will provide important new insights on cuprate high-T_{c} superconductivity and related quantum phases.

  View details for DOI 10.1103/PhysRevLett.127.197003

  View details for Web of Science ID 000717968300004

  View details for PubMedID 34797146

• Distinct Oxygen Redox Activities in Li2MO3 (M = Mn, Ru, Ir) ACS ENERGY LETTERS Zhuo, Z., Dai, K., Wu, J., Zhang, L., Tamura, N., Chuang, Y., Feng, J., Guo, J., Shen, Z., Liu, G., Pan, F., Yang, W. 2021; 6 (10): 3417-3424

  View details for DOI 10.1021/acsenergylett.1c01101

  View details for Web of Science ID 000707987500004

• Superconducting Fluctuations in Overdoped Bi2Sr2CaCu2O8+delta PHYSICAL REVIEW X He, Y., Chen, S., Li, Z., Zhao, D., Song, D., Yoshida, Y., Eisaki, H., Wu, T., Chen, X., Lu, D., Meingast, C., Devereaux, T. P., Birgeneau, R. J., Hashimoto, M., Lee, D., Shen, Z. 2021; 11 (3)

  View details for DOI 10.1103/PhysRevX.11.031068

  View details for Web of Science ID 000704695200001

• Evidence for quantum spin liquid behaviour in single-layer 1T-TaSe2 from scanning tunnelling microscopy NATURE PHYSICS Ruan, W., Chen, Y., Tang, S., Hwang, J., Tsai, H., Lee, R. L., Wu, M., Ryu, H., Kahn, S., Liou, F., Jia, C., Aikawa, A., Hwang, C., Wang, F., Choi, Y., Louie, S. G., Lee, P. A., Shen, Z., Mo, S., Crommie, M. F. 2021

  View details for DOI 10.1038/s41567-021-01321-0

  View details for Web of Science ID 000686522600001

• Quantum Photonic Interface for Tin-Vacancy Centers in Diamond PHYSICAL REVIEW X Rugar, A. E., Aghaeimeibodi, S., Riedel, D., Dory, C., Lu, H., McQuade, P. J., Shen, Z., Melosh, N. A., Vuckovic, J. 2021; 11 (3)

  View details for DOI 10.1103/PhysRevX.11.031021

  View details for Web of Science ID 000679149200001

• Evolution of the electronic structure in Ta2NiSe5 across the structural transition revealed by resonant inelastic x-ray scattering PHYSICAL REVIEW B Lu, H., Rossi, M., Kim, J., Yavas, H., Said, A., Nag, A., Garcia-Fernandez, M., Agrestini, S., Zhou, K., Jia, C., Moritz, B., Devereaux, T. P., Shen, Z., Lee, W. 2021; 103 (23)

  View details for DOI 10.1103/PhysRevB.103.235159

  View details for Web of Science ID 000668993500001

• Angle-resolved photoemission studies of quantum materials REVIEWS OF MODERN PHYSICS Sobota, J. A., He, Y., Shen, Z. 2021; 93 (2)

  View details for DOI 10.1103/RevModPhys.93.025006

  View details for Web of Science ID 000655978600001

• Imaging Dual-Moire Lattices in Twisted Bilayer Graphene Aligned on Hexagonal Boron Nitride Using Microwave Impedance Microscopy. Nano letters Huang, X., Chen, L., Tang, S., Jiang, C., Chen, C., Wang, H., Shen, Z., Wang, H., Cui, Y. 2021

  Abstract

  Moire superlattices (MSLs) formed in van der Waals materials have become a promising platform to realize novel two-dimensional electronic states. Angle-aligned trilayer structures can form two sets of MSLs which could potentially interfere. In this work, we directly image the moire patterns in both monolayer and twisted bilayer graphene aligned on hexagonal boron nitride (hBN), using combined scanning microwave impedance microscopy and conductive atomic force microscopy. Correlation of the two techniques reveals the contrast mechanism for the achieved ultrahigh spatial resolution (<2 nm). We observe two sets of MSLs with different periodicities in the trilayer stack. The smaller MSL breaks the 6-fold rotational symmetry and exhibits abrupt discontinuities at the boundaries of the larger MSL. Using a rigid atomic-stacking model, we demonstrate that the hBN layer considerably modifies the MSL of twisted bilayer graphene. We further analyze its effect on the reciprocal space spectrum of the dual-moire system.

  View details for DOI 10.1021/acs.nanolett.1c00601

  View details for PubMedID 33949872

• Magic Doping and Robust Superconductivity in Monolayer FeSe on Titanates. Advanced science (Weinheim, Baden-Wurttemberg, Germany) Jia, T., Chen, Z., Rebec, S. N., Hashimoto, M., Lu, D., Devereaux, T. P., Lee, D. H., Moore, R. G., Shen, Z. X. 2021; 8 (9): 2003454

  Abstract

  The enhanced superconductivity in monolayer FeSe on titanates opens a fascinating pathway toward the rational design of high-temperature superconductors. Utilizing the state-of-the-art oxide plus chalcogenide molecular beam epitaxy systems in situ connected to a synchrotron angle-resolved photoemission spectroscope, epitaxial LaTiO3 layers with varied atomic thicknesses are inserted between monolayer FeSe and SrTiO3, for systematic modulation of interfacial chemical potential. With the dramatic increase of electron accumulation at the LaTiO3/SrTiO3 surface, providing a substantial surge of work function mismatch across the FeSe/oxide interface, the charge transfer and the superconducting gap in the monolayer FeSe are found to remain markedly robust. This unexpected finding indicate the existence of an intrinsically anchored "magic" doping within the monolayer FeSe systems.

  View details for DOI 10.1002/advs.202003454

  View details for PubMedID 33977049

  View details for PubMedCentralID PMC8097367

• Cycling mechanism of Li2MnO3: Li-CO2 batteries and commonality on oxygen redox in cathode materials JOULE Zhuo, Z., Dai, K., Qiao, R., Wang, R., Wu, J., Liu, Y., Peng, J., Chen, L., Chuang, Y., Pan, F., Shen, Z., Liu, G., Li, H., Devereaux, T. P., Yang, W. 2021; 5 (4): 975-997

  View details for DOI 10.1016/j.joule.2021.02.004

  View details for Web of Science ID 000642473100022

• Magic Doping and Robust Superconductivity in Monolayer FeSe on Titanates ADVANCED SCIENCE Jia, T., Chen, Z., Rebec, S. N., Hashimoto, M., Lu, D., Devereaux, T. P., Lee, D., Moore, R. G., Shen, Z. 2021

  View details for DOI 10.1002/advs.202003454

  View details for Web of Science ID 000617867700001

• Ultrafast formation of domain walls of a charge density wave in SmTe 3 Physical Review B Trigo, M., Giraldo-Gallo, P., Clark, J., Kozina, M., Henighan, T., Jiang, M., Chollet, M., Fisher, I., Glownia, J., Katayama, T., Kirchmann, P., Leuenberger, D., Liu, H., Shen, Z., Zhu, D. 2021; 103 (5): 054109
• Anomalously strong near-neighbor attraction in doped 1D cuprate chains. Science (New York, N.Y.) Chen, Z., Wang, Y., Rebec, S. N., Jia, T., Hashimoto, M., Lu, D., Moritz, B., Moore, R. G., Devereaux, T. P., Shen, Z. 2021; 373 (6560): 1235-1239

  Abstract

  [Figure: see text].

  View details for DOI 10.1126/science.abf5174

  View details for PubMedID 34516788

• Narrow-linewidth tin-vacancy centers in diamond waveguides Rugar, A. E., Aghaeimeibodi, S., Dory, C., Lu, H., McQuade, P. J., Mishra, S., Sun, S., Shen, Z., Melosh, N. A., Vuckovic, J., IEEE IEEE. 2021

  View details for Web of Science ID 000831479801105

• Spectroscopic fingerprint of charge order melting driven by quantum fluctuations in a cuprate Nature Physics Lee, W., Zhou, K., Hepting, M., Li, J., Nag, A., Walters, A., Garcia-Fernandez, M., Robarts, H., Hashimoto, M., Lu, H., Nosarzewski, B., Song, D., Eisaki, H., Shen, Z., Moritz, B., Zaanen, J., Devereaux, T. 2021; 17 (1): 53-57

  View details for DOI 10.1038/s41567-020-01075-1

• Emergence of quasiparticles in a doped Mott insulator COMMUNICATIONS PHYSICS Wang, Y., He, Y., Wohlfeld, K., Hashimoto, M., Huang, E. W., Lu, D., Mo, S., Komiya, S., Jia, C., Moritz, B., Shen, Z., Devereaux, T. P. 2020; 3 (1)

  View details for DOI 10.1038/s42005-020-00480-5

  View details for Web of Science ID 000594380600003

• Spectroscopic fingerprint of charge order melting driven by quantum fluctuations in a cuprate (Aug, 10.1038/s41567-020-0993-7, 2020) NATURE PHYSICS Lee, W. S., Zhou, K., Hepting, M., Li, J., Nag, A., Walters, A. C., Garcia-Fernandez, M., Robarts, H. C., Hashimoto, M., Lu, H., Nosarzewski, B., Song, D., Eisaki, H., Shen, Z. X., Moritz, B., Zaanen, J., Devereaux, T. P. 2020

  View details for DOI 10.1038/s41567-020-01075-1

  View details for Web of Science ID 000578419100001

• Spectral weight reduction of two-dimensional electron gases at oxide surfaces across the ferroelectric transition SCIENTIFIC REPORTS Jaiban, P., Lu, M., Eknapakul, T., Chaiyachad, S., Yao, S. H., Pisitpipathsin, N., Unruan, M., Siriroj, S., He, R., Mo, S., Watcharapasorn, A., Yimnirun, R., Tokura, Y., Shen, Z., Hwang, H. Y., Maensiri, S., Meevasana, W. 2020; 10 (1): 16834

  Abstract

  The discovery of a two-dimensional electron gas (2DEG) at the [Formula: see text] interface has set a new platform for all-oxide electronics which could potentially exhibit the interplay among charge, spin, orbital, superconductivity, ferromagnetism and ferroelectricity. In this work, by using angle-resolved photoemission spectroscopy and conductivity measurement, we found the reduction of 2DEGs and the changes of the conductivity nature of some ferroelectric oxides including insulating Nb-lightly-substituted [Formula: see text], [Formula: see text] (BTO) and (Ca,Zr)-doped BTO across paraelectric-ferroelectric transition. We propose that these behaviours could be due to the increase of space-charge screening potential at the 2DEG/ferroelectric regions which is a result of the realignment of ferroelectric polarisation upon light irradiation. This finding suggests an opportunity for controlling the 2DEG at a bare oxide surface (instead of interfacial system) by using both light and ferroelectricity.

  View details for DOI 10.1038/s41598-020-73657-1

  View details for Web of Science ID 000577475100058

  View details for PubMedID 33033329

  View details for PubMedCentralID PMC7545169

• Narrow-Linewidth Tin-Vacancy Centers in a Diamond Waveguide ACS PHOTONICS Rugar, A. E., Dory, C., Aghaeimeibodi, S., Lu, H., Sun, S., Mishra, S., Shen, Z., Melosh, N. A., Vuckovic, J. 2020; 7 (9): 2356–61

  View details for DOI 10.1021/acsphotonics.0c00833

  View details for Web of Science ID 000573377300006

• Redox Mechanism in Na-Ion Battery Cathodes Probed by Advanced Soft X-Ray Spectroscopy FRONTIERS IN CHEMISTRY Wu, J., Shen, Z., Yang, W. 2020; 8

  View details for DOI 10.3389/fchem.2020.00816

  View details for Web of Science ID 000575965700001

• Quantum-well states in fractured crystals of the heavy-fermion material CeCoIn5 PHYSICAL REVIEW B Gauthier, N., Sobota, J. A., Hashimoto, M., Pfau, H., Lu, D., Bauer, E. D., Ronning, F., Kirchmann, P. S., Shen, Z. 2020; 102 (12)

  View details for DOI 10.1103/PhysRevB.102.125111

  View details for Web of Science ID 000566891800007

• Tuning time and energy resolution in time-resolved photoemission spectroscopy with nonlinear crystals JOURNAL OF APPLIED PHYSICS Gauthier, A., Sobota, J. A., Gauthier, N., Xu, K., Pfau, H., Rotundu, C. R., Shen, Z., Kirchmann, P. S. 2020; 128 (9)

  View details for DOI 10.1063/5.0018834

  View details for Web of Science ID 000567597300001

• Publisher Correction: Electronic structure of the parent compound of superconducting infinite-layer nickelates. Nature materials Hepting, M., Li, D., Jia, C. J., Lu, H., Paris, E., Tseng, Y., Feng, X., Osada, M., Been, E., Hikita, Y., Chuang, Y., Hussain, Z., Zhou, K. J., Nag, A., Garcia-Fernandez, M., Rossi, M., Huang, H. Y., Huang, D. J., Shen, Z. X., Schmitt, T., Hwang, H. Y., Moritz, B., Zaanen, J., Devereaux, T. P., Lee, W. S. 2020

  Abstract

  An amendment to this paper has been published and can be accessed via a link at the top of the paper.

  View details for DOI 10.1038/s41563-020-0761-1

  View details for PubMedID 32661388

• Metallic surface states in a correlated d-electron topological Kondo insulator candidate FeSb2. Proceedings of the National Academy of Sciences of the United States of America Xu, K., Chen, S., He, Y., He, J., Tang, S., Jia, C., Ma, E. Y., Mo, S., Lu, D., Hashimoto, M., Devereaux, T. P., Shen, Z. 2020

  Abstract

  The resistance of a conventional insulator diverges as temperature approaches zero. The peculiar low-temperature resistivity saturation in the 4f Kondo insulator (KI) SmB6 has spurred proposals of a correlation-driven topological Kondo insulator (TKI) with exotic ground states. However, the scarcity of model TKI material families leaves difficulties in disentangling key ingredients from irrelevant details. Here we use angle-resolved photoemission spectroscopy (ARPES) to study FeSb2, a correlated d-electron KI candidate that also exhibits a low-temperature resistivity saturation. On the (010) surface, we find a rich assemblage of metallic states with two-dimensional dispersion. Measurements of the bulk band structure reveal band renormalization, a large temperature-dependent band shift, and flat spectral features along certain high-symmetry directions, providing spectroscopic evidence for strong correlations. Our observations suggest that exotic insulating states resembling those in SmB6 and YbB12 may also exist in systems with d instead of f electrons.

  View details for DOI 10.1073/pnas.2002361117

  View details for PubMedID 32571928

• Visualization of Multifractal Superconductivity in a Two-Dimensional Transition Metal Dichalcogenide in the Weak-Disorder Regime. Nano letters Rubio-Verdu, C., Garci A-Garci A, A. M., Ryu, H., Choi, D., Zaldi Var, J., Tang, S., Fan, B., Shen, Z., Mo, S., Pascual, J. I., Ugeda, M. M. 2020

  Abstract

  Eigenstate multifractality is a distinctive feature of noninteracting disordered metals close to a metal-insulator transition, whose properties are expected to extend to superconductivity. While multifractality in three dimensions (3D) only develops near the critical point for specific strong-disorder strengths, multifractality in 2D systems is expected to be observable even for weak disorder. Here we provide evidence for multifractal features in the superconducting state of an intrinsic, weakly disordered single-layer NbSe2 by means of low-temperature scanning tunneling microscopy/spectroscopy. The superconducting gap, characterized by its width, depth, and coherence peaks' amplitude, shows a characteristic spatial modulation coincident with the periodicity of the quasiparticle interference pattern. The strong spatial inhomogeneity of the superconducting gap width, proportional to the local order parameter in the weak-disorder regime, follows a log-normal statistical distribution as well as a power-law decay of the two-point correlation function, in agreement with our theoretical model. Furthermore, the experimental singularity spectrum f(alpha) shows anomalous scaling behavior typical from 2D weakly disordered systems.

  View details for DOI 10.1021/acs.nanolett.0c01288

  View details for PubMedID 32463696

• Low work function in the 122-family of iron-based superconductors PHYSICAL REVIEW MATERIALS Pfau, H., Soifer, H., Sobota, J. A., Gauthier, A., Rotundu, C. R., Palmstrom, J. C., Fisher, I. R., Chen, G., Wen, H., Shen, Z., Kirchmann, P. S. 2020; 4 (3)

  View details for DOI 10.1103/PhysRevMaterials.4.034801

  View details for Web of Science ID 000517972500004

• Super resolution convolutional neural network for feature extraction in spectroscopic data REVIEW OF SCIENTIFIC INSTRUMENTS Peng, H., Gao, X., He, Y., Li, Y., Ji, Y., Liu, C., Ekahana, S. A., Pei, D., Liu, Z., Shen, Z., Chen, Y. 2020; 91 (3): 033905

  Abstract

  Two dimensional (2D) peak finding is a common practice in data analysis for physics experiments, which is typically achieved by computing the local derivatives. However, this method is inherently unstable when the local landscape is complicated or the signal-to-noise ratio of the data is low. In this work, we propose a new method in which the peak tracking task is formalized as an inverse problem, which thus can be solved with a convolutional neural network (CNN). In addition, we show that the underlying physics principle of the experiments can be used to generate the training data. By generalizing the trained neural network on real experimental data, we show that the CNN method can achieve comparable or better results than traditional derivative based methods. This approach can be further generalized in different physics experiments when the physical process is known.

  View details for DOI 10.1063/1.5132586

  View details for Web of Science ID 000521309700001

  View details for PubMedID 32259998

• Generation of Tin-Vacancy Centers in Diamond via Shallow Ion Implantation and Subsequent Diamond Overgrowth. Nano letters Rugar, A. E., Lu, H., Dory, C., Sun, S., McQuade, P. J., Shen, Z., Melosh, N. A., Vuckovic, J. 2020

  Abstract

  Group IV color centers in diamond have garnered great interest for their potential as optically active solid-state spin qubits. The future utilization of such emitters requires the development of precise site-controlled emitter generation techniques that are compatible with high-quality nanophotonic devices. This task is more challenging for color centers with large group IV impurity atoms, which are otherwise promising because of their predicted long spin coherence times without a dilution refrigerator. For example, when applied to the negatively charged tin-vacancy (SnV-) center, conventional site-controlled color center generation methods either damage the diamond surface or yield bulk spectra with unexplained features. Here we demonstrate a novel method to generate site-controlled SnV- centers with clean bulk spectra. We shallowly implant Sn ions through a thin implantation mask and subsequently grow a layer of diamond via chemical vapor deposition. This method can be extended to other color centers and integrated with quantum nanophotonic device fabrication.

  View details for DOI 10.1021/acs.nanolett.9b04495

  View details for PubMedID 32031821

• Dissociate lattice oxygen redox reactions from capacity and voltage drops of battery electrodes. Science advances Wu, J., Zhuo, Z., Rong, X., Dai, K., Lebens-Higgins, Z., Sallis, S., Pan, F., Piper, L. F., Liu, G., Chuang, Y., Hussain, Z., Li, Q., Zeng, R., Shen, Z., Yang, W. 2020; 6 (6): eaaw3871

  Abstract

  The oxygen redox (OR) activity is conventionally considered detrimental to the stability and kinetics of batteries. However, OR reactions are often confused by irreversible oxygen oxidation. Here, based on high-efficiency mapping of resonant inelastic x-ray scattering of both the transition metal and oxygen, we distinguish the lattice OR in Na0.6[Li0.2Mn0.8]O2 and compare it with Na2/3[Mg1/3Mn2/3]O2. Both systems display strong lattice OR activities but with distinct electrochemical stability. The comparison shows that the substantial capacity drop in Na0.6[Li0.2Mn0.8]O2 stems from non-lattice oxygen oxidations, and its voltage decay from an increasing Mn redox contribution upon cycling, contrasting those in Na2/3[Mg1/3Mn2/3]O2. We conclude that lattice OR is not the ringleader of the stability issue. Instead, irreversible oxygen oxidation and the changing cationic reactions lead to the capacity and voltage fade. We argue that lattice OR and other oxygen activities should/could be studied and treated separately to achieve viable OR-based electrodes.

  View details for DOI 10.1126/sciadv.aaw3871

  View details for PubMedID 32083173

• Electronic structure of the parent compound of superconducting infinite-layer nickelates. Nature materials Hepting, M., Li, D., Jia, C. J., Lu, H., Paris, E., Tseng, Y., Feng, X., Osada, M., Been, E., Hikita, Y., Chuang, Y., Hussain, Z., Zhou, K. J., Nag, A., Garcia-Fernandez, M., Rossi, M., Huang, H. Y., Huang, D. J., Shen, Z. X., Schmitt, T., Hwang, H. Y., Moritz, B., Zaanen, J., Devereaux, T. P., Lee, W. S. 2020

  Abstract

  The search continues for nickel oxide-based materials with electronic properties similar to cuprate high-temperature superconductors1-10. The recent discovery of superconductivity in the doped infinite-layer nickelate NdNiO2 (refs. 11,12) has strengthened these efforts. Here, we use X-ray spectroscopy and density functional theory to show that the electronic structure of LaNiO2 and NdNiO2, while similar to the cuprates, includes significant distinctions. Unlike cuprates, the rare-earth spacer layer in the infinite-layer nickelate supports a weakly interacting three-dimensional 5d metallic state, which hybridizes with a quasi-two-dimensional, strongly correlated state with [Formula: see text] symmetry in the NiO2 layers. Thus, the infinite-layer nickelate can be regarded as a sibling of the rare-earth intermetallics13-15, which are well known for heavy fermion behaviour, where the NiO2 correlated layers play an analogous role to the 4f states in rare-earth heavy fermion compounds. This Kondo- or Anderson-lattice-like 'oxide-intermetallic' replaces the Mott insulator as the reference state from which superconductivity emerges upon doping.

  View details for DOI 10.1038/s41563-019-0585-z

  View details for PubMedID 31959951

• Strong correlations and orbital texture in single-layer 1T-TaSe2 NATURE PHYSICS Chen, Y., Ruan, W., Wu, M., Tang, S., Ryu, H., Tsai, H., Lee, R., Kahn, S., Liou, F., Jia, C., Albertini, O. R., Xiong, H., Jia, T., Liu, Z., Sobota, J. A., Liu, A. Y., Moore, J. E., Shen, Z., Louie, S. G., Mo, S., Crommie, M. F. 2020

  View details for DOI 10.1038/s41567-019-0744-9

  View details for Web of Science ID 000508145800003

• Synergistic enhancement of electrocatalytic CO2 reduction to C2 oxygenates at nitrogen-doped nanodiamonds/Cu interface. Nature nanotechnology Wang, H., Tzeng, Y., Ji, Y., Li, Y., Li, J., Zheng, X., Yang, A., Liu, Y., Gong, Y., Cai, L., Li, Y., Zhang, X., Chen, W., Liu, B., Lu, H., Melosh, N. A., Shen, Z., Chan, K., Tan, T., Chu, S., Cui, Y. 2020

  Abstract

  To date, effective control over the electrochemical reduction of CO2 to multicarbon products (C≥2) has been very challenging. Here, we report a design principle for the creation of a selective yet robust catalytic interface for heterogeneous electrocatalysts in the reduction of CO2 to C2 oxygenates, demonstrated by rational tuning of an assembly of nitrogen-doped nanodiamonds and copper nanoparticles. The catalyst exhibits a Faradaic efficiency of ~63% towards C2 oxygenates at applied potentials of only -0.5V versus reversible hydrogen electrode. Moreover, this catalyst shows an unprecedented persistent catalytic performance up to 120h, with steady current and only 19% activity decay. Density functional theory calculations show that CO binding is strengthened at the copper/nanodiamond interface, suppressing CO desorption and promoting C2 production by lowering the apparent barrier for CO dimerization. The inherent compositional and electronic tunability of the catalyst assembly offers an unrivalled degree of control over the catalytic interface, and thereby the reaction energetics and kinetics.

  View details for DOI 10.1038/s41565-019-0603-y

  View details for PubMedID 31907442

• Site-controlled generation of tin-vacancy centers in diamond via shallow ion implantation and diamond overgrowth Rugar, A. E., Lu, H., Dory, C., Sun, S., McQuade, P. J., Shen, Z., Melosh, N. A., Vuckovic, J., IEEE IEEE. 2020

  View details for Web of Science ID 000612090000055

• Nematic Energy Scale and the Missing Electron Pocket in FeSe PHYSICAL REVIEW X Yi, M., Pfau, H., Zhang, Y., He, Y., Wu, H., Chen, T., Ye, Z. R., Hashimoto, M., Yu, R., Si, Q., Lee, D., Dai, P., Shen, Z., Lu, D. H., Birgeneau, R. J. 2019; 9 (4)

  View details for DOI 10.1103/PhysRevX.9.041049

  View details for Web of Science ID 000501491400001

• Spectroscopic Evidence for Electron-Boson Coupling in Electron-Doped Sr2IrO4 PHYSICAL REVIEW LETTERS Hu, Y., Chen, X., Peng, S., Lane, C., Matzelle, M., Sun, Z., Hashimoto, M., Lu, D., Schwier, E. F., Arita, M., Wu, T., Markiewicz, R. S., Shimada, K., Chen, X., Shen, Z., Bansil, A., Wilson, S. D., He, J. 2019; 123 (21): 216402

  Abstract

  The pseudogap, d-wave superconductivity and electron-boson coupling are three intertwined key ingredients in the phase diagram of the cuprates. Sr_{2}IrO_{4} is a 5d-electron counterpart of the cuprates in which both the pseudogap and a d-wave instability have been observed. Here, we report spectroscopic evidence for the presence of the third key player in electron-doped Sr_{2}IrO_{4}: electron-boson coupling. A kink in nodal dispersion is observed with an energy scale of ∼50  meV. The strength of the kink changes with doping, but the energy scale remains the same. These results provide the first noncuprate platform for exploring the relationship between the pseudogap, d-wave instability, and electron-boson coupling in doped Mott insulators.

  View details for DOI 10.1103/PhysRevLett.123.216402

  View details for Web of Science ID 000498063600005

  View details for PubMedID 31809181

• Band-dependent superconducting gap in SrFe2(As0.65P0.35)(2) studied by angle-resolved photoemission spectroscopy SCIENTIFIC REPORTS Suzuki, H., Kobayashi, T., Miyasaka, S., Okazaki, K., Yoshida, T., Horio, M., Ambolode, L. C., Ota, Y., Yamamoto, H., Shin, S., Hashimoto, M., Lu, D. H., Shen, Z., Tajima, S., Fujimori, A. 2019; 9: 16418

  Abstract

  The isovalent-substituted iron pnictide compound SrFe2(As1-xPx)2 exhibits multiple evidence for nodal superconductivity via various experimental probes, such as the penetration depth, nuclear magnetic resonance and specific heat measurements. The direct identification of the nodal superconducting (SC) gap structure is challenging, partly because the presence of nodes is not protected by symmetry but instead caused by an accidental sign change of the order parameter, and also because of the three-dimensionality of the electronic structure. We have studied the SC gaps of SrFe2(As0.65P0.35)2 in three-dimensional momentum space by synchrotron and laser-based angle-resolved photoemission spectroscopy. The three hole Fermi surfaces (FSs) at the zone center have SC gaps with different magnitudes, whereas the SC gaps of the electron FSs at the zone corner are almost isotropic and kz-independent. As a possible nodal SC gap structure, we propose that the SC gap of the outer hole FS changes sign around the Z-X [(0, 0, 2π) - (π, π, 2π)] direction.

  View details for DOI 10.1038/s41598-019-52887-y

  View details for Web of Science ID 000495611100010

  View details for PubMedID 31712663

  View details for PubMedCentralID PMC6848191

• Surface Photovoltage-Induced Ultralow Work Function Material for Thermionic Energy Converters ACS ENERGY LETTERS Schindler, P., Riley, D. C., Bargatin, I., Sahasrahuddhe, K., Schwede, J. W., Sun, S., Pianetta, P., Shen, Z., Howe, R. T., Melosh, N. A. 2019; 4 (10): 2436–43

  Abstract

  Low work function materials are essential for efficient thermionic energy converters (TECs), electronics, and electron emission devices. Much effort has been put into finding thermally stable material combinations that exhibit low work functions. Submonolayer coatings of alkali metals have proven to significantly reduce the work function; however, a work function less than 1 eV has not been reached. We report a record-low work function of 0.70 eV by inducing a surface photovoltage (SPV) in an n-type semiconductor with an alkali metal coating. Ultraviolet photoelectron spectroscopy indicates a work function of 1.06 eV for cesium/oxygen-activated GaAs consistent with density functional theory model predictions. By illuminating with a 532 nm laser we induce an additional shift down to 0.70 eV due to the SPV. Further, we apply the SPV to the collector of an experimental TEC and demonstrate an I-V curve shift consistent with the collector work function reduction. This method opens an avenue toward efficient TECs and next-generation electron emission devices.

  View details for DOI 10.1021/acsenergylett.9b01214

  View details for Web of Science ID 000490365500011

  View details for PubMedID 31633034

  View details for PubMedCentralID PMC6792473

• Momentum Dependence of the Nematic Order Parameter in Iron-Based Superconductors PHYSICAL REVIEW LETTERS Pfau, H., Chen, D., Yi, M., Hashimoto, M., Rotundu, C. R., Palmstrom, J. C., Chen, T., Dai, P., Straquadme, J., Hristov, A., Birgeneau, R. J., Fisher, I. R., Lu, D., Shen, Z. 2019; 123 (6)

  View details for DOI 10.1103/PhysRevLett.123.066402

  View details for Web of Science ID 000479034100010

• Manipulating Topological Domain Boundaries in the Single-Layer Quantum Spin Hall Insulator 1T'-WSe2. Nano letters Pedramrazi, Z., Herbig, C., Pulkin, A., Tang, S., Phillips, M., Wong, D., Ryu, H., Pizzochero, M., Chen, Y., Wang, F., Mele, E. J., Shen, Z., Mo, S., Yazyev, O. V., Crommie, M. F. 2019

  Abstract

  We report the creation and manipulation of structural phase boundaries in the single-layer quantum spin Hall insulator 1T'-WSe2 by means of scanning tunneling microscope tip pulses. We observe the formation of one-dimensional interfaces between topologically nontrivial 1T' domains having different rotational orientations, as well as induced interfaces between topologically nontrivial 1T' and topologically trivial 1H phases. Scanning tunneling spectroscopy measurements show that 1T'/1T' interface states are localized at domain boundaries, consistent with theoretically predicted unprotected interface modes that form dispersive bands in and around the energy gap of this quantum spin Hall insulator. We observe a qualitative difference in the experimental spectral line shape between topologically "unprotected" states at 1T'/1T' domain boundaries and protected states at 1T'/1H and 1T'/vacuum boundaries in single-layer WSe2.

  View details for DOI 10.1021/acs.nanolett.9b02157

  View details for PubMedID 31329449

• Nanodiamond Integration with Photonic Devices LASER & PHOTONICS REVIEWS Rodulaski, M., Zhang, J., Tzeng, Y., Lagoudakis, K. G., Ishiwata, H., Dory, C., Fischer, K. A., Kelaita, Y. A., Sun, S., Maurer, P. C., Alassaad, K., Ferro, G., Shen, Z., Melosh, N. A., Chu, S., Vuckovic, J. 2019

  View details for DOI 10.1002/lpor.201800316

  View details for Web of Science ID 000480009200001

• Visualization of an axion insulating state at the transition between 2 chiral quantum anomalous Hall states. Proceedings of the National Academy of Sciences of the United States of America Allen, M., Cui, Y., Yue Ma, E., Mogi, M., Kawamura, M., Fulga, I. C., Goldhaber-Gordon, D., Tokura, Y., Shen, Z. 2019

  Abstract

  Quantum-relativistic materials often host electronic phenomena with exotic spatial distributions. In particular, quantum anomalous Hall (QAH) insulators feature topological boundary currents whose chirality is determined by the magnetization orientation. However, understanding the microscopic nature of edge vs. bulk currents has remained a challenge due to the emergence of multidomain states at the phase transitions. Here we use microwave impedance microscopy (MIM) to directly image chiral edge currents and phase transitions in a magnetic topological insulator. Our images reveal a dramatic change in the edge state structure and an unexpected microwave response at the topological phase transition between the Chern number [Formula: see text] and [Formula: see text] states, consistent with the emergence of an insulating [Formula: see text] state. The magnetic transition width is independent of film thickness, but the transition pattern is distinct in differently initiated field sweeps. This behavior suggests that the [Formula: see text] state has 2 surface states with Hall conductivities of [Formula: see text] but with opposite signs.

  View details for DOI 10.1073/pnas.1818255116

  View details for PubMedID 31266887

• Mode-Selective Coupling of Coherent Phonons to the Bi2212 Electronic Band Structure PHYSICAL REVIEW LETTERS Yang, S., Sobota, J. A., He, Y., Leuenberger, D., Soifer, H., Eisaki, H., Kirchmann, P. S., Shen, Z. 2019; 122 (17): 176403

  Abstract

  Cuprate superconductors host a multitude of low-energy optical phonons. Using time- and angle-resolved photoemission spectroscopy, we study coherent phonons in Bi_{2}Sr_{2}Ca_{0.92}Y_{0.08}Cu_{2}O_{8+δ}. Sub-meV modulations of the electronic band structure are observed at frequencies of 3.94±0.01 and 5.59±0.06  THz. For the dominant mode at 3.94 THz, the amplitude of the band energy oscillation weakly increases as a function of momentum away from the node. Theoretical calculations allow identifying the observed modes as CuO_{2}-derived A_{1g} phonons. The Bi- and Sr-derived A_{1g} modes which dominate Raman spectra in the relevant frequency range are absent in our measurements. This highlights the mode selectivity for phonons coupled to the near-Fermi-level electrons, which originate from CuO_{2} planes and dictate thermodynamic properties.

  View details for DOI 10.1103/PhysRevLett.122.176403

  View details for Web of Science ID 000467042000022

  View details for PubMedID 31107058

• Band-Resolved Imaging of Photocurrent in a Topological Insulator PHYSICAL REVIEW LETTERS Soifer, H., Gauthier, A., Kemper, A. F., Rotundu, C. R., Yang, S., Xiong, H., Lu, D., Hashimoto, M., Kirchmann, P. S., Sobota, J. A., Shen, Z. 2019; 122 (16): 167401

  Abstract

  We study the microscopic origins of photocurrent generation in the topological insulator Bi_{2}Se_{3} via time- and angle-resolved photoemission spectroscopy. We image the unoccupied band structure as it evolves following a circularly polarized optical excitation and observe an asymmetric electron population in momentum space, which is the spectroscopic signature of a photocurrent. By analyzing the rise times of the population we identify which occupied and unoccupied electronic states are coupled by the optical excitation. We conclude that photocurrents can only be excited via resonant optical transitions coupling to spin-orbital textured states. Our work provides a microscopic understanding of how to control photocurrents in systems with spin-orbit coupling and broken inversion symmetry.

  View details for DOI 10.1103/PhysRevLett.122.167401

  View details for Web of Science ID 000466440000009

  View details for PubMedID 31075004

• Coherent order parameter dynamics in SmTe3 PHYSICAL REVIEW B Trigo, M., Giraldo-Gallo, P., Kozina, M. E., Henighan, T., Jiang, M. P., Liu, H., Clark, J. N., Chollet, M., Glownia, J. M., Zhu, D., Katayama, T., Leuenberger, D., Kirchmann, P. S., Fisher, I. R., Shen, Z. X., Reis, D. A. 2019; 99 (10)

  View details for DOI 10.1103/PhysRevB.99.104111

  View details for Web of Science ID 000462892000004

• Scanning microwave imaging of optically patterned Ge2Sb2Te5 APPLIED PHYSICS LETTERS Johnston, S. R., Ng, E., Fong, S. W., Mok, W. Y., Park, J., Zalden, P., Sakdinawat, A., Wong, H., Mabuchi, H., Shen, Z. 2019; 114 (9)

  View details for DOI 10.1063/1.5052018

  View details for Web of Science ID 000460820600042

• Electronic structure of the quadrupolar ordered heavy-fermion compound YbRu2Ge2 measured by angle-resolved photoemission PHYSICAL REVIEW B Pfau, H., Rosenberg, E. W., Massat, P., Moritz, B., Hashimoto, M., Lu, D., Fisher, I. R., Shen, Z. 2019; 99 (7)

  View details for DOI 10.1103/PhysRevB.99.075159

  View details for Web of Science ID 000459935900001

• Fermi surface reconstruction in electron-doped cuprates without antiferromagnetic long-range order. Proceedings of the National Academy of Sciences of the United States of America He, J., Rotundu, C. R., Scheurer, M. S., He, Y., Hashimoto, M., Xu, K., Wang, Y., Huang, E. W., Jia, T., Chen, S., Moritz, B., Lu, D., Lee, Y. S., Devereaux, T. P., Shen, Z. 2019; 116 (9): 3449–53

  Abstract

  Fermi surface (FS) topology is a fundamental property of metals and superconductors. In electron-doped cuprate Nd2-x Ce x CuO4 (NCCO), an unexpected FS reconstruction has been observed in optimal- and overdoped regime (x = 0.15-0.17) by quantum oscillation measurements (QOM). This is all the more puzzling because neutron scattering suggests that the antiferromagnetic (AFM) long-range order, which is believed to reconstruct the FS, vanishes before x = 0.14. To reconcile the conflict, a widely discussed external magnetic-field-induced AFM long-range order in QOM explains the FS reconstruction as an extrinsic property. Here, we report angle-resolved photoemission (ARPES) evidence of FS reconstruction in optimal- and overdoped NCCO. The observed FSs are in quantitative agreement with QOM, suggesting an intrinsic FS reconstruction without field. This reconstructed FS, despite its importance as a basis to understand electron-doped cuprates, cannot be explained under the traditional scheme. Furthermore, the energy gap of the reconstruction decreases rapidly near x = 0.17 like an order parameter, echoing the quantum critical doping in transport. The totality of the data points to a mysterious order between x = 0.14 and 0.17, whose appearance favors the FS reconstruction and disappearance defines the quantum critical doping. A recent topological proposal provides an ansatz for its origin.

  View details for PubMedID 30808739

• High Reversibility of Lattice Oxygen Redox Quantified by Direct Bulk Probes of Both Anionic and Cationic Redox Reactions JOULE Dai, K., Wu, J., Zhuo, Z., Li, Q., Sallis, S., Mao, J., Ai, G., Sun, C., Li, Z., Gent, W. E., Chueh, W. C., Chuang, Y., Zeng, R., Shen, Z., Pan, F., Yan, S., Piper, L. J., Hussain, Z., Liu, G., Yang, W. 2019; 3 (2): 518–41

  View details for DOI 10.1016/j.joule.2018.11.014

  View details for Web of Science ID 000460076100019

• Recording interfacial currents on the subnanometer length and femtosecond time scale by terahertz emission. Science advances Ma, E. Y., Guzelturk, B., Li, G., Cao, L., Shen, Z., Lindenberg, A. M., Heinz, T. F. 2019; 5 (2): eaau0073

  Abstract

  Electron dynamics at interfaces is a subject of great scientific interest and technological importance. Detailed understanding of such dynamics requires access to the angstrom length scale defining interfaces and the femtosecond time scale characterizing interfacial motion of electrons. In this context, the most precise and general way to remotely measure charge dynamics is through the transient current flow and the associated electromagnetic radiation. Here, we present quantitative measurements of interfacial currents on the subnanometer length and femtosecond time scale by recording the emitted terahertz radiation following ultrafast laser excitation. We apply this method to interlayer charge transfer in heterostructures of two transition metal dichalcogenide monolayers less than 0.7 nm apart. We find that charge relaxation and separation occur in less than 100 fs. This approach allows us to unambiguously determine the direction of current flow, to demonstrate a charge transfer efficiency of order unity, and to characterize saturation effects.

  View details for PubMedID 30783622

• Imaging quantum spin Hall edges in monolayer WTe2. Science advances Shi, Y., Kahn, J., Niu, B., Fei, Z., Sun, B., Cai, X., Francisco, B. A., Wu, D., Shen, Z., Xu, X., Cobden, D. H., Cui, Y. 2019; 5 (2): eaat8799

  Abstract

  A two-dimensional (2D) topological insulator exhibits the quantum spin Hall (QSH) effect, in which topologically protected conducting channels exist at the sample edges. Experimental signatures of the QSH effect have recently been reported in an atomically thin material, monolayer WTe2. Here, we directly image the local conductivity of monolayer WTe2 using microwave impedance microscopy, establishing beyond doubt that conduction is indeed strongly localized to the physical edges at temperatures up to 77 K and above. The edge conductivity shows no gap as a function of gate voltage, and is suppressed by magnetic field as expected. We observe additional conducting features which can be explained by edge states following boundaries between topologically trivial and nontrivial regions. These observations will be critical for interpreting and improving the properties of devices incorporating WTe2. Meanwhile, they reveal the robustness of the QSH channels and the potential to engineer them in the monolayer material platform.

  View details for PubMedID 30783621

• Detailed band structure of twinned and detwinned BaFe2As2 studied with angle-resolved photoemission spectroscopy PHYSICAL REVIEW B Pfau, H., Rotundu, C. R., Palmstrom, J. C., Chen, S. D., Hashimoto, M., Lu, D., Kemper, A. F., Fisher, I. R., Shen, Z. 2019; 99 (3)

  View details for DOI 10.1103/PhysRevB.99.035118

  View details for Web of Science ID 000455362400002

• Incoherent strange metal sharply bounded by a critical doping in Bi2212. Science (New York, N.Y.) Chen, S. D., Hashimoto, M. n., He, Y. n., Song, D. n., Xu, K. J., He, J. F., Devereaux, T. P., Eisaki, H. n., Lu, D. H., Zaanen, J. n., Shen, Z. X. 2019; 366 (6469): 1099–1102

  Abstract

  In normal metals, macroscopic properties are understood using the concept of quasiparticles. In the cuprate high-temperature superconductors, the metallic state above the highest transition temperature is anomalous and is known as the "strange metal." We studied this state using angle-resolved photoemission spectroscopy. With increasing doping across a temperature-independent critical value pc ~ 0.19, we observed that near the Brillouin zone boundary, the strange metal, characterized by an incoherent spectral function, abruptly reconstructs into a more conventional metal with quasiparticles. Above the temperature of superconducting fluctuations, we found that the pseudogap also discontinuously collapses at the very same value of pc These observations suggest that the incoherent strange metal is a distinct state and a prerequisite for the pseudogap; such findings are incompatible with existing pseudogap quantum critical point scenarios.

  View details for DOI 10.1126/science.aaw8850

  View details for PubMedID 31780552

• Monitoring Charge Separation Dynamics Using THz Emission Spectroscopy Guzelturk, B., Ma, E., Li, G., Cao, L., Shen, Z., Heinz, T., Lindenberg, A., IEEE IEEE. 2019

  View details for Web of Science ID 000482226301162

• Frequency Tunable Single-Photon Emission From a Single Atomic Defect in a Solid Sun, S., Zhang, J., Fischer, K. A., Burek, M. J., Dory, C., Lagoudakis, K. G., Tzeng, Y., Radulaski, M., Kelaita, Y., Safavi-Naeini, A., Shen, Z., Melosh, N. A., Chu, S., Loncar, M., Vuckovic, J., IEEE IEEE. 2019

  View details for Web of Science ID 000482226303114

• Momentum-resolved resonant inelastic soft X-ray scattering (qRIXS) endstation at the ALS Journal of Electron Spectroscopy and Related Phenomena Chuang, Y., Feng, X., Cruz, A., Hanzel, K., Brown, A., Spucces, A., Frano, A., Lee, W., Kim, J., Chen, Y., Smith, B., Pepper, J. S., Shao, Y., Huang, S., Wray, L., Gullikson, E., Shen, Z., Devereaux, T. P., Tremsin, A., Yang, W., Guo, J., Duarte, R., Hussain, Z. 2019: 146897
• Dichotomy of the photo-induced 2-dimensional electron gas on SrTiO3 surface terminations. Proceedings of the National Academy of Sciences of the United States of America Rebec, S. N., Jia, T. n., Sohail, H. M., Hashimoto, M. n., Lu, D. n., Shen, Z. X., Moore, R. G. 2019

  Abstract

  Oxide materials are important candidates for the next generation of electronics due to a wide array of desired properties, which they can exhibit alone or when combined with other materials. While SrTiO3 (STO) is often considered a prototypical oxide, it, too, hosts a wide array of unusual properties, including a 2-dimensional electron gas (2DEG), which can form at the surface when exposed to ultraviolet (UV) light. Using layer-by-layer growth of high-quality STO films, we show that the 2DEG only forms with the SrO termination and not with the TiO2 termination, contrary to expectation. This dichotomy of the observed angle-resolved photoemission spectroscopy (ARPES) spectra is similarly seen in BaTiO3 (BTO), in which the 2DEG is only observed for BaO-terminated films. These results will allow for a deeper understanding and better control of the electronic structure of titanate films, substrates, and heterostructures.

  View details for DOI 10.1073/pnas.1821937116

  View details for PubMedID 31391304

• Epitaxial growth of TiSe2/TiO2 heterostructure 2D MATERIALS Jia, T., Rebec, S. N., Tang, S., Xu, K., Sohail, H. M., Hashimoto, M., Lu, D., Moore, R. G., Shen, Z. 2019; 6 (1)

  View details for DOI 10.1088/2053-1583/aaeadf

  View details for Web of Science ID 000451023100001

• Three-dimensional collective charge excitations in electron-doped copper oxide superconductors NATURE Hepting, M., Chaix, L., Huang, E. W., Fumagalli, R., Peng, Y. Y., Moritz, B., Kummer, K., Brookes, N. B., Lee, W. C., Hashimoto, M., Sarkar, T., He, J., Rotundu, C. R., Lee, Y. S., Greene, R. L., Braicovich, L., Ghiringhelli, G., Shen, Z. X., Devereaux, T. P., Lee, W. S. 2018; 563 (7731): 374-+

  View details for DOI 10.1038/s41586-018-0648-3

  View details for Web of Science ID 000450048400054

• Rapid change of superconductivity and electron-phonon coupling through critical doping in Bi-2212 SCIENCE He, Y., Hashimoto, M., Song, D., Chen, S., He, J., Vishik, I. M., Moritz, B., Lee, D., Nagaosa, N., Zaanen, J., Devereaux, T. P., Yoshida, Y., Eisaki, H., Lu, D. H., Shen, Z. 2018; 362 (6410): 62-+

  View details for DOI 10.1126/science.aar3394

  View details for Web of Science ID 000446547100041

• Spectral Evidence for Emergent Order in Ba1-xNaxFe2As2 PHYSICAL REVIEW LETTERS Yi, M., Frano, A., Lu, D. H., He, Y., Wang, M., Frandsen, B. A., Kemper, A. F., Yu, R., Si, Q., Wang, L., He, M., Hardy, F., Schweiss, P., Adelmann, P., Wolf, T., Hashimoto, M., Mo, S., Hussain, Z., Le Tacon, M., Boehmer, A. E., Lee, D., Shen, Z., Meingast, C., Birgeneau, R. J. 2018; 121 (12)

  View details for DOI 10.1103/PhysRevLett.121.127001

  View details for Web of Science ID 000444961000004

• Orbital-dependent spin textures in Bi2Se3 quantum well states PHYSICAL REVIEW B Lin, C., Gotlieb, K., Jozwiak, C., Hussain, Z., Lanzara, A. 2018; 98 (7)

  View details for DOI 10.1103/PhysRevB.98.075149

  View details for Web of Science ID 000442806600005

• Cavity-Enhanced Raman Emission from a Single Color Center in a Solid. Physical review letters Sun, S., Zhang, J. L., Fischer, K. A., Burek, M. J., Dory, C., Lagoudakis, K. G., Tzeng, Y., Radulaski, M., Kelaita, Y., Safavi-Naeini, A., Shen, Z., Melosh, N. A., Chu, S., Loncar, M., Vuckovic, J. 2018; 121 (8): 083601

  Abstract

  We demonstrate cavity-enhanced Raman emission from a single atomic defect in a solid. Our platform is a single silicon-vacancy center in diamond coupled with a monolithic diamond photonic crystal cavity. The cavity enables an unprecedented frequency tuning range of the Raman emission (100GHz) that significantly exceeds the spectral inhomogeneity of silicon-vacancy centers in diamond nanostructures. We also show that the cavity selectively suppresses the phonon-induced spontaneous emission that degrades the efficiency of Raman photon generation. Our results pave the way towards photon-mediated many-body interactions between solid-state quantum emitters in a nanophotonic platform.

  View details for PubMedID 30192607

• Observation of topologically protected states at crystalline phase boundaries in single-layer WSe2 NATURE COMMUNICATIONS Ugeda, M. M., Pulkin, A., Tang, S., Ryu, H., Wu, Q., Zhang, Y., Wong, D., Pedramrazi, Z., Martin-Recio, A., Chen, Y., Wang, F., Shen, Z., Mo, S., Yazyev, O. V., Crommie, M. F. 2018; 9: 3401

  Abstract

  Transition metal dichalcogenide materials are unique in the wide variety of structural and electronic phases they exhibit in the two-dimensional limit. Here we show how such polymorphic flexibility can be used to achieve topological states at highly ordered phase boundaries in a new quantum spin Hall insulator (QSHI), 1T'-WSe2. We observe edge states at the crystallographically aligned interface between a quantum spin Hall insulating domain of 1T'-WSe2 and a semiconducting domain of 1H-WSe2 in contiguous single layers. The QSHI nature of single-layer 1T'-WSe2 is verified using angle-resolved photoemission spectroscopy to determine band inversion around a 120 meV energy gap, as well as scanning tunneling spectroscopy to directly image edge-state formation. Using this edge-state geometry we confirm the predicted penetration depth of one-dimensional interface states into the two-dimensional bulk of a QSHI for a well-specified crystallographic direction. These interfaces create opportunities for testing predictions of the microscopic behavior of topologically protected boundary states.

  View details for PubMedID 30143617

• 'Molecular anvlils' for stercially controlled mechanochemistry under hydrostatic pressure Yan, H., Schreiner, P., Mao, W., Shen, Z., Melosh, N. AMER CHEMICAL SOC. 2018

  View details for Web of Science ID 000447609104001

• An Ultrastrong Double-Layer Nanodiamond Interface for Stable Lithium Metal Anodes JOULE Liu, Y., Tzeng, Y., Lin, D., Pei, A., Lu, H., Melosh, N. A., Shen, Z., Chu, S., Cui, Y. 2018; 2 (8): 1595–1609

  View details for DOI 10.1016/j.joule.2018.05.007

  View details for Web of Science ID 000441627400022

• Experimental measurement of the diamond nucleation landscape reveals classical and nonclassical features. Proceedings of the National Academy of Sciences of the United States of America Gebbie, M. A., Ishiwata, H., McQuade, P. J., Petrak, V., Taylor, A., Freiwald, C., Dahl, J. E., Carlson, R. M., Fokin, A. A., Schreiner, P. R., Shen, Z., Nesladek, M., Melosh, N. A. 2018

  Abstract

  Nucleation is a core scientific concept that describes the formation of new phases and materials. While classical nucleation theory is applied across wide-ranging fields, nucleation energy landscapes have never been directly measured at the atomic level, and experiments suggest that nucleation rates often greatly exceed the predictions of classical nucleation theory. Multistep nucleation via metastable states could explain unexpectedly rapid nucleation in many contexts, yet experimental energy landscapes supporting such mechanisms are scarce, particularly at nanoscale dimensions. In this work, we measured the nucleation energy landscape of diamond during chemical vapor deposition, using a series of diamondoid molecules as atomically defined protonuclei. We find that 26-carbon atom clusters, which do not contain a single bulk atom, are postcritical nuclei and measure the nucleation barrier to be more than four orders of magnitude smaller than prior bulk estimations. These data support both classical and nonclassical concepts for multistep nucleation and growth during the gas-phase synthesis of diamond and other semiconductors. More broadly, these measurements provide experimental evidence that agrees with recent conceptual proposals of multistep nucleation pathways with metastable molecular precursors in diverse processes, ranging from cloud formation to protein crystallization, and nanoparticle synthesis.

  View details for PubMedID 30068609

• Persistent low-energy phonon broadening near the charge-order q vector in the bilayer cuprate Bi2Sr2CaCu2O8+delta PHYSICAL REVIEW B He, Y., Wu, S., Song, Y., Lee, W., Said, A. H., Alatas, A., Bosak, A., Girard, A., Souliou, S. M., Ruiz, A., Hepting, M., Bluschke, M., Schierle, E., Weschke, E., Lee, J., Jang, H., Huang, H., Hashimoto, M., Lu, D., Song, D., Yoshida, Y., Eisaki, H., Shen, Z., Birgeneau, R. J., Yi, M., Frano, A. 2018; 98 (3)

  View details for DOI 10.1103/PhysRevB.98.035102

  View details for Web of Science ID 000436938600002

• Coincident onset of charge-density-wave order at a quantum critical point in underdoped YBa2Cu3Ox PHYSICAL REVIEW B Jang, H., Lee, W., Song, S., Nojiri, H., Matsuzawa, S., Yasumura, H., Huang, H., Liu, Y., Porras, J., Minola, M., Keimer, B., Hastings, J., Zhu, D., Devereaux, T. P., Shen, Z., Kao, C., Lee, J. 2018; 97 (22)

  View details for DOI 10.1103/PhysRevB.97.224513

  View details for Web of Science ID 000435332500003

• Anomalous Hall effect in ZrTe5 NATURE PHYSICS Liang, T., Lin, J., Gibson, Q., Kushwaha, S., Liu, M., Wang, W., Xiong, H., Sobota, J. A., Hashimoto, M., Kirchmann, P. S., Shen, Z., Cava, R. J., Ong, N. P. 2018; 14 (5): 451-+

  View details for DOI 10.1038/s41567-018-0078-z

  View details for Web of Science ID 000431301800016

• Resonant inelastic x-ray scattering studies of magnons and bimagnons in the lightly doped cuprate La2-xSrxCuO4 PHYSICAL REVIEW B Chaix, L., Huang, E. W., Gerber, S., Lu, X., Jia, C., Huang, Y., McNally, D. E., Wang, Y., Vernay, F. H., Keren, A., Shi, M., Moritz, B., Shen, Z., Schmitt, T., Devereaux, T. P., Lee, W. 2018; 97 (15)

  View details for DOI 10.1103/PhysRevB.97.155144

  View details for Web of Science ID 000430459400001

• Dehybridization of f and d states in the heavy-fermion system YbRh2Si2 PHYSICAL REVIEW B Leuenberger, D., Sobota, J. A., Yang, S., Pfau, H., Kim, D., Mo, S., Fisk, Z., Kirchmann, P. S., Shen, Z. 2018; 97 (16)

  View details for DOI 10.1103/PhysRevB.97.165108

  View details for Web of Science ID 000429447900002

• Optically coupled methods for microwave impedance microscopy REVIEW OF SCIENTIFIC INSTRUMENTS Johnston, S. R., Ma, E., Shen, Z. 2018; 89 (4): 043703

  Abstract

  Scanning Microwave Impedance Microscopy (MIM) measurement of photoconductivity with 50 nm resolution is demonstrated using a modulated optical source. The use of a modulated source allows for the measurement of photoconductivity in a single scan without a reference region on the sample, as well as removing most topographical artifacts and enhancing signal to noise as compared with unmodulated measurement. A broadband light source with a tunable monochrometer is then used to measure energy resolved photoconductivity with the same methodology. Finally, a pulsed optical source is used to measure local photo-carrier lifetimes via MIM, using the same 50 nm resolution tip.

  View details for PubMedID 29716321

• Sterically controlled mechanochemistry under hydrostatic pressure NATURE Yan, H., Yang, F., Pan, D., Lin, Y., Hohman, J., Solis-Ibarra, D., Li, F., Dahl, J. P., Carlson, R. K., Tkachenko, B. A., Fokin, A. A., Schreiner, P. R., Galli, G., Mao, W. L., Shen, Z., Melosh, N. A. 2018; 554 (7693): 505-+

  Abstract

  Mechanical stimuli can modify the energy landscape of chemical reactions and enable reaction pathways, offering a synthetic strategy that complements conventional chemistry. These mechanochemical mechanisms have been studied extensively in one-dimensional polymers under tensile stress using ring-opening and reorganization, polymer unzipping and disulfide reduction as model reactions. In these systems, the pulling force stretches chemical bonds, initiating the reaction. Additionally, it has been shown that forces orthogonal to the chemical bonds can alter the rate of bond dissociation. However, these bond activation mechanisms have not been possible under isotropic, compressive stress (that is, hydrostatic pressure). Here we show that mechanochemistry through isotropic compression is possible by molecularly engineering structures that can translate macroscopic isotropic stress into molecular-level anisotropic strain. We engineer molecules with mechanically heterogeneous components-a compressible ('soft') mechanophore and incompressible ('hard') ligands. In these 'molecular anvils', isotropic stress leads to relative motions of the rigid ligands, anisotropically deforming the compressible mechanophore and activating bonds. Conversely, rigid ligands in steric contact impede relative motion, blocking reactivity. We combine experiments and computations to demonstrate hydrostatic-pressure-driven redox reactions in metal-organic chalcogenides that incorporate molecular elements that have heterogeneous compressibility, in which bending of bond angles or shearing of adjacent chains activates the metal-chalcogen bonds, leading to the formation of the elemental metal. These results reveal an unexplored reaction mechanism and suggest possible strategies for high-specificity mechanosynthesis.

  View details for PubMedID 29469090

• Monochromatic Photocathodes from Graphene-Stabilized Diamondoids NANO LETTERS Yan, H., Narasimha, K. T., Denlinger, J., Li, F., Mo, S., Hohman, J., Dahl, J. P., Carlson, R. K., Tkachenko, B. A., Fokin, A. A., Schreiner, P. R., Hussain, Z., Shen, Z., Melosh, N. A. 2018; 18 (2): 1099–1103

  Abstract

  The monochromatic photoemission from diamondoid monolayers provides a new strategy to create electron sources with low energy dispersion and enables compact electron guns with high brightness and low beam emittance for aberration-free imaging, lithography, and accelerators. However, these potential applications are hindered by degradation of diamondoid monolayers under photon irradiation and electron bombardment. Here, we report a graphene-protected diamondoid monolayer photocathode with 4-fold enhancement of stability compared to the bare diamondoid counterpart. The single-layer graphene overcoating preserves the monochromaticity of the photoelectrons, showing 12.5 meV ful width at half-maximum distribution of kinetic energy. Importantly, the graphene coating effectively suppresses desorption of the diamondoid monolayer, enhancing its thermal stability by at least 100 K. Furthermore, by comparing the decay rate at different photon energies, we identify electron bombardment as the principle decay pathway for diamondoids under graphene protection. This provides a generic approach for stabilizing volatile species on photocathode surfaces, which could greatly improve performance of electron emitters.

  View details for PubMedID 29286670

• Strongly Cavity-Enhanced Spontaneous Emission from Silicon-Vacancy Centers in Diamond NANO LETTERS Zhang, J., Sun, S., Burek, M. J., Dory, C., Tzeng, Y., Fischer, K. A., Kelaita, Y., Lardakis, K. G., Radulaski, M., Shen, Z., Melosh, N. A., Chu, S., Loncar, M., Vuckovic, J. 2018; 18 (2): 1360–65

  Abstract

  Quantum emitters are an integral component for a broad range of quantum technologies, including quantum communication, quantum repeaters, and linear optical quantum computation. Solid-state color centers are promising candidates for scalable quantum optics due to their long coherence time and small inhomogeneous broadening. However, once excited, color centers often decay through phonon-assisted processes, limiting the efficiency of single-photon generation and photon-mediated entanglement generation. Herein, we demonstrate strong enhancement of spontaneous emission rate of a single silicon-vacancy center in diamond embedded within a monolithic optical cavity, reaching a regime in which the excited-state lifetime is dominated by spontaneous emission into the cavity mode. We observe 10-fold lifetime reduction and 42-fold enhancement in emission intensity when the cavity is tuned into resonance with the optical transition of a single silicon-vacancy center, corresponding to 90% of the excited-state energy decay occurring through spontaneous emission into the cavity mode. We also demonstrate the largest coupling strength (g/2π = 4.9 ± 0.3 GHz) and cooperativity (C = 1.4) to date for color-center-based cavity quantum electrodynamics systems, bringing the system closer to the strong coupling regime.

  View details for DOI 10.1021/acs.nanolett.7b05075

  View details for Web of Science ID 000425559700102

  View details for PubMedID 29377701

• Electronic structure of monolayer 1T'-MoTe2 grown by molecular beam epitaxy APL MATERIALS Tang, S., Zhang, C., Jia, C., Ryu, H., Hwang, C., Hashimoto, M., Lu, D., Liu, Z., Devereaux, T. P., Shen, Z., Mo, S. 2018; 6 (2)

  View details for DOI 10.1063/1.5004700

  View details for Web of Science ID 000426999900008

• Persistent Charge-Density-Wave Order in Single-Layer TaSe2 NANO LETTERS Ryu, H., Chen, Y., Kim, H., Tsai, H., Tang, S., Jiang, J., Liou, F., Kahn, S., Jia, C., Omrani, A. A., Shim, J., Hussain, Z., Shen, Z., Kim, K., Min, B., Hwang, C., Crommie, M. F., Mo, S. 2018; 18 (2): 689–94

  Abstract

  We present the electronic characterization of single-layer 1H-TaSe2 grown by molecular beam epitaxy using a combined angle-resolved photoemission spectroscopy, scanning tunneling microscopy/spectroscopy, and density functional theory calculations. We demonstrate that 3 × 3 charge-density-wave (CDW) order persists despite distinct changes in the low energy electronic structure highlighted by the reduction in the number of bands crossing the Fermi energy and the corresponding modification of Fermi surface topology. Enhanced spin-orbit coupling and lattice distortion in the single-layer play a crucial role in the formation of CDW order. Our findings provide a deeper understanding of the nature of CDW order in the two-dimensional limit.

  View details for PubMedID 29300484

• Charge density wave order in 2D transition metal dichalcogenides The 54th Winter Annual Conference of the Korean Vacuum Society Ryu, H., Chen, Y., Ugeda, M. M., Kim, H., Zhang, Y., Tsai, H., Tang, S., Jiang, J., Liou, F., Kahn, S., Jia, C., Omrani, A. A., Shim, J., Hussain, Z., Shen, Z., Kim, K., II Min, B., Hwang, C., Crommie, M. F., Mo, S. 2018: 85
• Electronic characterization of the coexisting charge density wave and superconductivity in single-layer NbSe2 at T = 1 K Verhandlungen der Deutschen Physikalischen Gesellschaft Carmen, R., Choi, D., Ryu, H., Mo, S., Shen, Z., Pascual, J. I., Ugeda, M. M. 2018; 50 (14)
• Modification of Transition-Metal Redox by Interstitial Water in Hexacyanometalate Electrodes for Sodium-Ion Batteries JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Wu, J., Song, J., Dai, K., Zhuo, Z., Wray, L., Liu, G., Shen, Z., Zeng, R., Lu, Y., Yang, W. 2017; 139 (50): 18358–64

  Abstract

  A sodium-ion battery (SIB) solution is attractive for grid-scale electrical energy storage. Low-cost hexacyanometalate is a promising electrode material for SIBs because of its easy synthesis and open framework. Most hexacyanometalate-based SIBs work with aqueous electrolyte, and interstitial water in the material has been found to strongly affect the electrochemical profile, but the mechanism remains elusive. Here we provide a comparative study of the transition-metal redox in hexacyanometalate electrodes with and without interstitial water based on soft X-ray absorption spectroscopy and theoretical calculations. We found distinct transition-metal redox sequences in hydrated and anhydrated NaxMnFe(CN)6·zH2O. The Fe and Mn redox in hydrated electrodes are separated and are at different potentials, leading to two voltage plateaus. On the contrary, mixed Fe and Mn redox in the same potential range is found in the anhydrated system. This work reveals for the first time how transition-metal redox in batteries is strongly affected by interstitial molecules that are seemingly spectators. The results suggest a fundamental mechanism based on three competing factors that determine the transition-metal redox potentials. Because most hexacyanometalate electrodes contain water, this work directly reveals the mechanism of how interstitial molecules could define the electrochemical profile, especially for electrodes based on transition-metal redox with well-defined spin states.

  View details for PubMedID 29169239

• Revealing the Coulomb interaction strength in a cuprate superconductor PHYSICAL REVIEW B Yang, S., Sobota, J. A., He, Y., Wang, Y., Leuenberger, D., Soifer, H., Hashimoto, M., Lu, D. H., Eisaki, H., Moritz, B., Devereaux, T. P., Kirchmann, P. S., Shen, Z. 2017; 96 (24)

  View details for DOI 10.1103/PhysRevB.96.245112

  View details for Web of Science ID 000417487400004

• Role of the orbital degree of freedom in iron-based superconductors NPJ QUANTUM MATERIALS Yi, M., Zhang, Y., Shen, Z., Lu, D. 2017; 2

  View details for DOI 10.1038/s41535-017-0059-y

  View details for Web of Science ID 000414584500001

• Dispersive charge density wave excitations in Bi2Sr2CaCu2O8+delta NATURE PHYSICS Chaix, L., Ghiringhelli, G., Peng, Y. Y., Hashimoto, M., Moritz, B., Kummer, K., Brookes, N. B., He, Y., Chen, S., Ishida, S., Yoshida, Y., Eisaki, H., Salluzzo, M., Braicovich, L., Shen, Z., Devereaux, T. P., Lee, W. 2017; 13 (10): 952-+

  View details for DOI 10.1038/NPHYS4157

  View details for Web of Science ID 000412181200014

• Stripes developed at the strong limit of nematicity in FeSe film NATURE PHYSICS Li, W., Zhang, Y., Deng, P., Xu, Z., Mo, S., Yi, M., Ding, H., Hashimoto, M., Moore, R. G., Lu, D., Chen, X., Shen, Z., Xue, Q. 2017; 13 (10): 957-+

  View details for DOI 10.1038/NPHYS4186

  View details for Web of Science ID 000412181200015

• Taking control of spin currents NATURE Shen, Z., Sobota, J. 2017; 549 (7673): 464–65

  View details for PubMedID 28959972

• Measurement of surface acoustic wave resonances in ferroelectric domains by microwave microscopy JOURNAL OF APPLIED PHYSICS Johnston, S. R., Yang, Y., Cui, Y., Ma, E., Kampfe, T., Eng, L. M., Zhou, J., Chen, Y., Lu, M., Shen, Z. 2017; 122 (7)

  View details for DOI 10.1063/1.4997474

  View details for Web of Science ID 000408060900013

• Large thermopower from dressed quasiparticles in the layered cobaltates and rhodates PHYSICAL REVIEW B Chen, S., He, Y., Zong, A., Zhang, Y., Hashimoto, M., Zhang, B., Yao, S., Chen, Y., Zhou, J., Chen, Y., Mo, S., Hussain, Z., Lu, D., Shen, Z. 2017; 96 (8)

  View details for DOI 10.1103/PhysRevB.96.081109

  View details for Web of Science ID 000407550400001

• ARPES study of the epitaxially grown topological crystalline insulator SnTe(111) JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Zhang, Y., Liu, Z., Zhou, B., Kim, Y., Yang, L., Ryu, H., Hwang, C., Chen, Y., Hussain, Z., Shen, Z., Mo, S. 2017; 219: 35–40

  View details for DOI 10.1016/j.elspec.2016.10.003

  View details for Web of Science ID 000411302600006

• HfSe2 and ZrSe2: Two-dimensional semiconductors with native high-κ oxides. Science advances Mleczko, M. J., Zhang, C., Lee, H. R., Kuo, H. H., Magyari-Köpe, B., Moore, R. G., Shen, Z. X., Fisher, I. R., Nishi, Y., Pop, E. 2017; 3 (8): e1700481

  Abstract

  The success of silicon as a dominant semiconductor technology has been enabled by its moderate band gap (1.1 eV), permitting low-voltage operation at reduced leakage current, and the existence of SiO2 as a high-quality "native" insulator. In contrast, other mainstream semiconductors lack stable oxides and must rely on deposited insulators, presenting numerous compatibility challenges. We demonstrate that layered two-dimensional (2D) semiconductors HfSe2 and ZrSe2 have band gaps of 0.9 to 1.2 eV (bulk to monolayer) and technologically desirable "high-κ" native dielectrics HfO2 and ZrO2, respectively. We use spectroscopic and computational studies to elucidate their electronic band structure and then fabricate air-stable transistors down to three-layer thickness with careful processing and dielectric encapsulation. Electronic measurements reveal promising performance (on/off ratio > 106; on current, ~30 μA/μm), with native oxides reducing the effects of interfacial traps. These are the first 2D materials to demonstrate technologically relevant properties of silicon, in addition to unique compatibility with high-κ dielectrics, and scaling benefits from their atomically thin nature.

  View details for DOI 10.1126/sciadv.1700481

  View details for PubMedID 28819644

  View details for PubMedCentralID PMC5553816

• Femtosecond electron-phonon lock-in by photoemission and x-ray free-electron laser SCIENCE Gerber, S., Yang, S., Zhu, D., Soifer, H., Sobota, J. A., Rebec, S., Lee, J. J., Jia, T., Moritz, B., Jia, C., Gauthier, A., Li, Y., Leuenberger, D., Zhang, Y., Chaix, L., Li, W., Jang, H., Lee, J., Yi, M., Dakovski, G. L., Song, S., Glownia, J. M., Nelson, S., Kim, K. W., Chuang, Y., Hussain, Z., Moore, R. G., Devereaux, T. P., Lee, W., Kirchmann, P. S., Shen, Z. 2017; 357 (6346): 71–74

  Abstract

  The interactions that lead to the emergence of superconductivity in iron-based materials remain a subject of debate. It has been suggested that electron-electron correlations enhance electron-phonon coupling in iron selenide (FeSe) and related pnictides, but direct experimental verification has been lacking. Here we show that the electron-phonon coupling strength in FeSe can be quantified by combining two time-domain experiments into a "coherent lock-in" measurement in the terahertz regime. X-ray diffraction tracks the light-induced femtosecond coherent lattice motion at a single phonon frequency, and photoemission monitors the subsequent coherent changes in the electronic band structure. Comparison with theory reveals a strong enhancement of the coupling strength in FeSe owing to correlation effects. Given that the electron-phonon coupling affects superconductivity exponentially, this enhancement highlights the importance of the cooperative interplay between electron-electron and electron-phonon interactions.

  View details for PubMedID 28684521

• Visualizing dispersive features in 2D image via minimum gradient method REVIEW OF SCIENTIFIC INSTRUMENTS He, Y., Wang, Y., Shen, Z. 2017; 88 (7): 073903

  Abstract

  We developed a minimum gradient based method to track ridge features in a 2D image plot, which is a typical data representation in many momentum resolved spectroscopy experiments. Through both analytic formulation and numerical simulation, we compare this new method with existing DC (distribution curve) based and higher order derivative based analyses. We find that the new method has good noise resilience and enhanced contrast especially for weak intensity features and meanwhile preserves the quantitative local maxima information from the raw image. An algorithm is proposed to extract 1D ridge dispersion from the 2D image plot, whose quantitative application to angle-resolved photoemission spectroscopy measurements on high temperature superconductors is demonstrated.

  View details for DOI 10.1063/1.4993919

  View details for Web of Science ID 000406773700027

  View details for PubMedID 28764533

• Quantum spin Hall state in monolayer 1T '-WTe2 NATURE PHYSICS Tang, S., Zhang, C., Wong, D., Pedramrazi, Z., Tsai, H., Jia, C., Moritz, B., Claassen, M., Ryu, H., Kahn, S., Jiang, J., Yan, H., Hashimoto, M., Lu, D., Moore, R. G., Hwang, C., Hwang, C., Hussain, Z., Chen, Y., Ugeda, M. M., Liu, Z., Xie, X., Devereaux, T. P., Crommie, M. F., Mo, S., Shen, Z. 2017; 13 (7): 683-+

  View details for DOI 10.1038/NPHYS4174

  View details for Web of Science ID 000404629900018

• Strongly three-dimensional electronic structure and Fermi surfaces of SrFe2(As0.65P0.35)(2): Comparison with BaFe2(As1-xPx)(2) (vol 89, 184513, 2014) PHYSICAL REVIEW B Suzuki, H., Kobayashi, T., Miyasaka, S., Yoshida, T., Okazaki, K., Ambolode, L. C., Ideta, S., Yi, M., Hashimoto, M., Lu, D. H., Shen, Z., Ono, K., Kumigashira, H., Tajima, S., Fujimori, A. 2017; 95 (17)

  View details for DOI 10.1103/PhysRevB.95.179901

  View details for Web of Science ID 000401998400005

• Three-dimensional nature of the band structure of ZrTe5 measured by high-momentum-resolution photoemission spectroscopy PHYSICAL REVIEW B Xiong, H., Sobota, J. A., Yang, S., Soifer, H., Gauthier, A., Lu, M., Lv, Y., Yao, S., Lu, D., Hashimoto, M., Kirchmann, P. S., Chen, Y., Shen, Z. 2017; 95 (19)

  View details for DOI 10.1103/PhysRevB.95.195119

  View details for Web of Science ID 000401229800001

• Nonequilibrium lattice-driven dynamics of stripes in nickelates using time-resolved x-ray scattering PHYSICAL REVIEW B Lee, W. S., Kung, Y. F., Moritz, B., Coslovich, G., Kaindl, R. A., Chuang, Y. D., Moore, R. G., Lu, D. H., Kirchmann, P. S., ROBINSON, J. S., Minitti, M. P., Dakovski, G., Schlotter, W. F., Turner, J. J., Gerber, S., Sasagawa, T., Hussain, Z., Shen, Z. X., Devereaux, T. P. 2017; 95 (12)

  View details for DOI 10.1103/PhysRevB.95.121105

  View details for Web of Science ID 000396014600002

• Unusual nodal behaviors of the superconducting gap in the iron-based superconductor Ba(Fe0.65Ru0.35)(2)As-2: Effects of spin-orbit coupling PHYSICAL REVIEW B Liu, L., Okazaki, K., Yoshida, T., Suzuki, H., Horio, M., Ambolode, L. C., Xu, J., Ideta, S., Hashimoto, M., Lu, D. H., Shen, Z., Ota, Y., Shin, S., Nakajima, M., Ishida, S., Kihou, K., Lee, C. H., Iyo, A., Eisaki, H., Mikami, T., Kakeshita, T., Yamakawa, Y., Kontani, H., Uchida, S., Fujimori, A. 2017; 95 (10)

  View details for DOI 10.1103/PhysRevB.95.104504

  View details for Web of Science ID 000396000700005

• Hybrid metal-organic chalcogenide nanowires with electrically conductive inorganic core through diamondoid-directed assembly. Nature materials Yan, H., Hohman, J. N., Li, F. H., Jia, C., Solis-Ibarra, D., Wu, B., Dahl, J. E., Carlson, R. M., Tkachenko, B. A., Fokin, A. A., Schreiner, P. R., Vailionis, A., Kim, T. R., Devereaux, T. P., Shen, Z., Melosh, N. A. 2017; 16 (3): 349-355

  Abstract

  Controlling inorganic structure and dimensionality through structure-directing agents is a versatile approach for new materials synthesis that has been used extensively for metal-organic frameworks and coordination polymers. However, the lack of 'solid' inorganic cores requires charge transport through single-atom chains and/or organic groups, limiting their electronic properties. Here, we report that strongly interacting diamondoid structure-directing agents guide the growth of hybrid metal-organic chalcogenide nanowires with solid inorganic cores having three-atom cross-sections, representing the smallest possible nanowires. The strong van der Waals attraction between diamondoids overcomes steric repulsion leading to a cis configuration at the active growth front, enabling face-on addition of precursors for nanowire elongation. These nanowires have band-like electronic properties, low effective carrier masses and three orders-of-magnitude conductivity modulation by hole doping. This discovery highlights a previously unexplored regime of structure-directing agents compared with traditional surfactant, block copolymer or metal-organic framework linkers.

  View details for DOI 10.1038/nmat4823

  View details for PubMedID 28024157

• Vertical-Substrate MPCVD Epitaxial Nanodiamond Growth. Nano letters Tzeng, Y., Zhang, J. L., Lu, H., Ishiwata, H., Dahl, J., Carlson, R. M., Yan, H., Schreiner, P. R., Vuckovic, J., Shen, Z., Melosh, N., Chu, S. 2017

  Abstract

  Color center-containing nanodiamonds have many applications in quantum technologies and biology. Diamondoids, molecular-sized diamonds have been used as seeds in chemical vapor deposition (CVD) growth. However, optimizing growth conditions to produce high crystal quality nanodiamonds with color centers requires varying growth conditions that often leads to ad-hoc and time-consuming, one-at-a-time testing of reaction conditions. In order to rapidly explore parameter space, we developed a microwave plasma CVD technique using a vertical, rather than horizontally oriented stage-substrate geometry. With this configuration, temperature, plasma density, and atomic hydrogen density vary continuously along the vertical axis of the substrate. This variation allowed rapid identification of growth parameters that yield single crystal diamonds down to 10 nm in size and 75 nm diameter optically active center silicon-vacancy (Si-V) nanoparticles. Furthermore, this method may provide a means of incorporating a wide variety of dopants in nanodiamonds without ion irradiation damage.

  View details for DOI 10.1021/acs.nanolett.6b04543

  View details for PubMedID 28182433

• Ubiquitous strong electron-phonon coupling at the interface of FeSe/SrTiO3 NATURE COMMUNICATIONS Zhang, C., Liu, Z., Chen, Z., Xie, Y., He, R., Tang, S., He, J., Li, W., Jia, T., Rebec, S. N., Ma, E. Y., Yan, H., Hashimoto, M., Lu, D., Mo, S., Hikita, Y., Moore, R. G., Hwang, H. Y., Lee, D., Shen, Z. 2017; 8

  Abstract

  The observation of replica bands in single-unit-cell FeSe on SrTiO3 (STO)(001) by angle-resolved photoemission spectroscopy (ARPES) has led to the conjecture that the coupling between FeSe electrons and the STO phonons are responsible for the enhancement of Tc over other FeSe-based superconductors. However the recent observation of a similar superconducting gap in single-unit-cell FeSe/STO(110) raised the question of whether a similar mechanism applies. Here we report the ARPES study of the electronic structure of FeSe/STO(110). Similar to the results in FeSe/STO(001), clear replica bands are observed. We also present a comparative study of STO(001) and STO(110) bare surfaces, and observe similar replica bands separated by approximately the same energy, indicating this coupling is a generic feature of the STO surfaces and interfaces. Our findings suggest that the large superconducting gaps observed in FeSe films grown on different STO surface terminations are likely enhanced by a common mechanism.

  View details for DOI 10.1038/ncomms14468

  View details for Web of Science ID 000393739700001

  View details for PubMedCentralID PMC5311057

• Coexistence of Replica Bands and Superconductivity in FeSe Monolayer Films. Physical review letters Rebec, S. N., Jia, T., Zhang, C., Hashimoto, M., Lu, D., Moore, R. G., Shen, Z. 2017; 118 (6): 067002-?

  Abstract

  To elucidate the mechanisms behind the enhanced T_{c} in monolayer (1 ML) FeSe on SrTiO_{3} (STO), we grew highly strained 1 ML FeSe on the rectangular (100) face of rutile TiO_{2}, and observed the coexistence of replica bands and superconductivity with a T_{c} of 63 K. From the similar T_{c} between this system and 1ML FeSe on STO (001), we conclude that strain and dielectric constant are likely unimportant to the enhanced T_{c} in these systems. A systematic comparison of 1 ML FeSe on TiO_{2} with other systems in the FeSe family shows that while charge transfer alone can enhance T_{c}, it is only with the addition of interfacial electron-phonon coupling that T_{c} can be increased to the level seen in 1 ML FeSe on STO.

  View details for DOI 10.1103/PhysRevLett.118.067002

  View details for PubMedID 28234508

• Back-gated graphene anode for more efficient thermionic energy converters NANO ENERGY Yuan, H., Riley, D. C., Shen, Z., Pianetta, P. A., Melosh, N. A., Howe, R. T. 2017; 32: 67-72

  View details for DOI 10.1016/j.nanoen.2016.12.027

  View details for Web of Science ID 000397003700009

• Modular soft x-ray spectrometer for applications in energy sciences and quantum materials. The Review of scientific instruments Chuang, Y., Shao, Y., Cruz, A., Hanzel, K., Brown, A., Frano, A., Qiao, R., Smith, B., Domning, E., Huang, S., Wray, L. A., Lee, W., Shen, Z., Devereaux, T. P., Chiou, J., Pong, W., Yashchuk, V. V., Gullikson, E., Reininger, R., Yang, W., Guo, J., Duarte, R., Hussain, Z. 2017; 88 (1): 013110-?

  Abstract

  Over the past decade, the advances in grating-based soft X-ray spectrometers have revolutionized the soft X-ray spectroscopies in materials research. However, these novel spectrometers are mostly dedicated designs, which cannot be easily adopted for applications with diverging demands. Here we present a versatile spectrometer design concept based on the Hettrick-Underwood optical scheme that uses modular mechanical components. The spectrometer's optics chamber can be used with gratings operated in either inside or outside orders, and the detector assembly can be reconfigured accordingly. The spectrometer can be designed to have high spectral resolution, exceeding 10 000 resolving power when using small source (∼1μm) and detector pixels (∼5μm) with high line density gratings (∼3000 lines/mm), or high throughput at moderate resolution. We report two such spectrometers with slightly different design goals and optical parameters in this paper. We show that the spectrometer with high throughput and large energy window is particularly useful for studying the sustainable energy materials. We demonstrate that the extensive resonant inelastic X-ray scattering (RIXS) map of battery cathode material LiNi1/3Co1/3Mn1/3O2 can be produced in few hours using such a spectrometer. Unlike analyzing only a handful of RIXS spectra taken at selected excitation photon energies across the elemental absorption edges to determine various spectral features like the localized dd excitations and non-resonant fluorescence emissions, these features can be easily identified in the RIXS maps. Studying such RIXS maps could reveal novel transition metal redox in battery compounds that are sometimes hard to be unambiguously identified in X-ray absorption and emission spectra. We propose that this modular spectrometer design can serve as the platform for further customization to meet specific scientific demands.

  View details for DOI 10.1063/1.4974356

  View details for PubMedID 28147697

• Dispersive charge density wave excitations in Bi2Sr2CaCu2O8+δ Dispersive charge density wave excitations in Bi2Sr2CaCu2O8+δ He, Y., Ishida, S., Yoshida, Y., Eisaki, H., Salluzzo, M., Braicovich, L., Shen, Z., Devereaux, T., Lee, W. 2017; 2 (3): 1

  View details for DOI 10.1038/nphys4157

• Basic Energy Sciences Roundtable: Opportunities for Basic Research at the Frontiers of XFEL Ultrafast Science Heinz, T., Shpyrko, O., Basov, D., Berrah, N., Bucksbaum, P., Devereaux, T., Fritz, D., Gaffney, K., Gessner, O., Gopalan, V., Hasan, Z., Lanzara, A., Martinez, T., Millis, A., Mukamel, S., Murnane, M., Nelson, K., Prasankumar, R., Reis, D., Schafer, K., Scholes, G., Shen, Z., Stolow, A., Wen, H., Wolf, M., et al U.S. Department of Energy, Office of Scientific and Technical Information. United States. 2017
• Complete Coherent Control of Silicon-Vacancies in Diamond Nanopillars Containing Single Defect Centers Zhang, J., Lagoudakis, K. G., Tzeng, Y., Dory, C., Radulaski, M., Kelaita, Y., Fischer, K. A., Shen, Z., Melosh, N. A., Chu, S., Vuckovic, J., IEEE IEEE. 2017

  View details for Web of Science ID 000427296200411

• Distinct Electronic Structure for the Extreme Magnetoresistance in YSb PHYSICAL REVIEW LETTERS He, J., Zhang, C., Ghimire, N. J., Liang, T., Jia, C., Jiang, J., Tang, S., Chen, S., He, Y., Mo, S., Hwang, C. C., Hashimoto, M., Lu, D. H., Moritz, B., Devereaux, T. P., Chen, Y. L., Mitchell, J. F., Shen, Z. 2016; 117 (26)

  Abstract

  An extreme magnetoresistance (XMR) has recently been observed in several nonmagnetic semimetals. Increasing experimental and theoretical evidence indicates that the XMR can be driven by either topological protection or electron-hole compensation. Here, by investigating the electronic structure of a XMR material, YSb, we present spectroscopic evidence for a special case which lacks topological protection and perfect electron-hole compensation. Further investigations reveal that a cooperative action of a substantial difference between electron and hole mobility and a moderate carrier compensation might contribute to the XMR in YSb.

  View details for DOI 10.1103/PhysRevLett.117.267201

  View details for PubMedID 28059532

• Ideal charge-density-wave order in the high-field state of superconducting YBCO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Jang, H., Lee, W., Nojiri, H., Matsuzawa, S., Yasumura, H., Nie, L., Maharaj, A. V., Gerber, S., Liu, Y., Mehta, A., Bonn, D. A., Liang, R., Hardy, W. N., Burns, C. A., Islam, Z., Song, S., Hastings, J., Devereaux, T. P., Shen, Z., Kivelson, S. A., Kao, C., Zhu, D., Lee, J. 2016; 113 (51): 14645-14650

  Abstract

  The existence of charge-density-wave (CDW) correlations in cuprate superconductors has now been established. However, the nature of the CDW ground state has remained uncertain because disorder and the presence of superconductivity typically limit the CDW correlation lengths to only a dozen unit cells or less. Here we explore the field-induced 3D CDW correlations in extremely pure detwinned crystals of YBa2Cu3O2 (YBCO) ortho-II and ortho-VIII at magnetic fields in excess of the resistive upper critical field ([Formula: see text]) where superconductivity is heavily suppressed. We observe that the 3D CDW is unidirectional and possesses a long in-plane correlation length as well as significant correlations between neighboring CuO2 planes. It is significant that we observe only a single sharply defined transition at a critical field proportional to [Formula: see text], given that the field range used in this investigation overlaps with other high-field experiments including quantum oscillation measurements. The correlation volume is at least two to three orders of magnitude larger than that of the zero-field CDW. This is by far the largest CDW correlation volume observed in any cuprate crystal and so is presumably representative of the high-field ground state of an "ideal" disorder-free cuprate.

  View details for DOI 10.1073/pnas.1612849113

  View details for Web of Science ID 000390044900047

  View details for PubMedID 27930313

  View details for PubMedCentralID PMC5187671

• Selenium capped monolayer NbSe2 for two-dimensional superconductivity studies PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS Onishi, S., Ugeda, M. M., Zhang, Y., Chen, Y., Ojeda-Aristizabal, C., Ryu, H., Mo, S., Hussain, Z., Shen, Z., Crommie, M. F., Zettl, A. 2016; 253 (12): 2396-2399

  View details for DOI 10.1002/pssb.201600235

  View details for Web of Science ID 000390339000019

• Spin-resolved photoemission study of epitaxially grown MoSe2 and WSe2 thin films JOURNAL OF PHYSICS-CONDENSED MATTER Mo, S., Hwang, C., Zhang, Y., Fanciulli, M., Muff, S., Dil, J. H., Shen, Z., Hussain, Z. 2016; 28 (45)

  View details for DOI 10.1088/0953-8984/28/45/454001

  View details for Web of Science ID 000385439100001

• Unconventional Correlation between Quantum Hall Transport Quantization and Bulk State Filling in Gated Graphene Devices PHYSICAL REVIEW LETTERS Cui, Y., Wen, B., Ma, E. Y., Diankov, G., Han, Z., Amet, F., Taniguchi, T., Watanabe, K., Goldhaber-Gordon, D., Dean, C. R., Shen, Z. 2016; 117 (18)

  Abstract

  We report simultaneous transport and scanning microwave impedance microscopy to examine the correlation between transport quantization and filling of the bulk Landau levels in the quantum Hall regime in gated graphene devices. Surprisingly, a comparison of these measurements reveals that quantized transport typically occurs below the complete filling of bulk Landau levels, when the bulk is still conductive. This result points to a revised understanding of transport quantization when carriers are accumulated by gating. We discuss the implications on transport study of the quantum Hall effect in graphene and related topological states in other two-dimensional electron systems.

  View details for DOI 10.1103/PhysRevLett.117.186601

  View details for Web of Science ID 000390227100011

  View details for PubMedID 27835026

• Directly Characterizing the Relative Strength and Momentum Dependence of Electron-Phonon Coupling Using Resonant Inelastic X-Ray Scattering PHYSICAL REVIEW X Devereaux, T. P., Shvaika, A. M., Wu, K., Wohlfeld, K., Jia, C. J., Wang, Y., Moritz, B., Chaix, L., Lee, W., Shen, Z., Ghiringhelli, G., Braicovich, L. 2016; 6 (4)

  View details for DOI 10.1103/PhysRevX.6.041019

  View details for Web of Science ID 000390219700002

• Spin-polarized surface resonances accompanying topological surface state formation NATURE COMMUNICATIONS Jozwiak, C., Sobota, J. A., Gotlieb, K., Kemper, A. F., Rotundu, C. R., Birgeneau, R. J., Hussain, Z., Lee, D., Shen, Z., Lanzara, A. 2016; 7

  Abstract

  Topological insulators host spin-polarized surface states born out of the energetic inversion of bulk bands driven by the spin-orbit interaction. Here we discover previously unidentified consequences of band-inversion on the surface electronic structure of the topological insulator Bi2Se3. By performing simultaneous spin, time, and angle-resolved photoemission spectroscopy, we map the spin-polarized unoccupied electronic structure and identify a surface resonance which is distinct from the topological surface state, yet shares a similar spin-orbital texture with opposite orientation. Its momentum dependence and spin texture imply an intimate connection with the topological surface state. Calculations show these two distinct states can emerge from trivial Rashba-like states that change topology through the spin-orbit-induced band inversion. This work thus provides a compelling view of the coevolution of surface states through a topological phase transition, enabled by the unique capability of directly measuring the spin-polarized unoccupied band structure.

  View details for DOI 10.1038/ncomms13143

  View details for Web of Science ID 000385548800001

  View details for PubMedID 27739428

  View details for PubMedCentralID PMC5067600

• Distinctive orbital anisotropy observed in the nematic state of a FeSe thin film PHYSICAL REVIEW B Zhang, Y., Yi, M., Liu, Z., Li, W., Lee, J. J., Moore, R. G., Hashimoto, M., Nakajima, M., Eisaki, H., Mo, S., Hussain, Z., Devereaux, T. P., Shen, Z., Lu, D. H. 2016; 94 (11)

  View details for DOI 10.1103/PhysRevB.94.115153

  View details for Web of Science ID 000384065700002

• Superconducting Gap Anisotropy in Monolayer FeSe Thin Film PHYSICAL REVIEW LETTERS Zhang, Y., Lee, J. J., Moore, R. G., Li, W., Yi, M., Hashimoto, M., Lu, D. H., Devereaux, T. P., Lee, D., Shen, Z. 2016; 117 (11)

  Abstract

  Superconductivity originates from pairing of electrons near the Fermi energy. The Fermi surface topology and pairing symmetry are thus two pivotal characteristics of a superconductor. Superconductivity in one monolayer (1 ML) FeSe thin film has attracted great interest recently due to its intriguing interfacial properties and possibly high superconducting transition temperature over 65 K. Here, we report high-resolution measurements of the Fermi surface and superconducting gaps in 1 ML FeSe using angle-resolved photoemission spectroscopy. Two ellipselike electron pockets are clearly resolved overlapping with each other at the Brillouin zone corner. The superconducting gap is nodeless but moderately anisotropic, which puts strong constraint on determining the pairing symmetry. The gap maxima locate on the d_{xy} bands along the major axis of the ellipse and four gap minima are observed at the intersections of electron pockets. The gap maximum location combined with the Fermi surface geometry deviate from a single d-wave, extended s-wave or s_{±} gap function, suggesting an important role of the multiorbital nature of Fermi surface and orbital-dependent pairing in 1 ML FeSe. The gap minima location may be explained by a sign change on the electron pockets, or a competition between intra- and interorbital pairing.

  View details for DOI 10.1103/PhysRevLett.117.117001

  View details for PubMedID 27661715

• Quantitative analysis of effective height of probes in microwave impedance microscopy REVIEW OF SCIENTIFIC INSTRUMENTS Wei, Z., Ma, E. Y., Cui, Y., Johnston, S., Yang, Y., Agarwal, K., Kelly, M. A., Shen, Z., Chen, X. 2016; 87 (9)

  Abstract

  A quantitative approach is used to determine an effective height of probe beyond which the capacitance contribution is not significant in microwave impedance microscopy (MIM). We compare the effective height for three different modes of measurement, i.e., capacitance C(l) (l is the tip-sample distance), derivative of capacitance (C'(l)), and second derivative of capacitance (C″(l)). We discuss the effects of tip geometry and sample properties such as relative permittivity and sample height on the effective height with examples and analyze the implication on the spatial resolution of MIM. Finally, our results are verified by microwave impedance microscopy (MIM) measurement.

  View details for DOI 10.1063/1.4962242

  View details for PubMedID 27782549

• Evolution of the Valley Position in Bulk Transition-Metal Chalcogenides and Their Monolayer Limit. Nano letters Yuan, H., Liu, Z., Xu, G., Zhou, B., Wu, S., Dumcenco, D., Yan, K., Zhang, Y., Mo, S., Dudin, P., Kandyba, V., Yablonskikh, M., Barinov, A., Shen, Z., Zhang, S., Huang, Y., Xu, X., Hussain, Z., Hwang, H. Y., Cui, Y., Chen, Y. 2016; 16 (8): 4738-4745

  Abstract

  Layered transition metal chalcogenides with large spin orbit coupling have recently sparked much interest due to their potential applications for electronic, optoelectronic, spintronics, and valleytronics. However, most current understanding of the electronic structure near band valleys in momentum space is based on either theoretical investigations or optical measurements, leaving the detailed band structure elusive. For example, the exact position of the conduction band valley of bulk MoS2 remains controversial. Here, using angle-resolved photoemission spectroscopy with submicron spatial resolution (micro-ARPES), we systematically imaged the conduction/valence band structure evolution across representative chalcogenides MoS2, WS2, and WSe2, as well as the thickness dependent electronic structure from bulk to the monolayer limit. These results establish a solid basis to understand the underlying valley physics of these materials, and also provide a link between chalcogenide electronic band structure and their physical properties for potential valleytronics applications.

  View details for DOI 10.1021/acs.nanolett.5b05107

  View details for PubMedID 27357620

• Picosecond Electric-Field-Induced Threshold Switching in Phase-Change Materials. Physical review letters Zalden, P., Shu, M. J., Chen, F., Wu, X., Zhu, Y., Wen, H., Johnston, S., Shen, Z., Landreman, P., Brongersma, M., Fong, S. W., Wong, H. P., Sher, M., Jost, P., Kaes, M., Salinga, M., von Hoegen, A., Wuttig, M., Lindenberg, A. M. 2016; 117 (6): 067601-?

  Abstract

  Many chalcogenide glasses undergo a breakdown in electronic resistance above a critical field strength. Known as threshold switching, this mechanism enables field-induced crystallization in emerging phase-change memory. Purely electronic as well as crystal nucleation assisted models have been employed to explain the electronic breakdown. Here, picosecond electric pulses are used to excite amorphous Ag_{4}In_{3}Sb_{67}Te_{26}. Field-dependent reversible changes in conductivity and pulse-driven crystallization are observed. The present results show that threshold switching can take place within the electric pulse on subpicosecond time scales-faster than crystals can nucleate. This supports purely electronic models of threshold switching and reveals potential applications as an ultrafast electronic switch.

  View details for DOI 10.1103/PhysRevLett.117.067601

  View details for PubMedID 27541475

• Charge density wave order in 1D mirror twin boundaries of single-layer MoSe2 NATURE PHYSICS Barja, S., Wickenburg, S., Liu, Z., Zhang, Y., Ryu, H., Ugeda, M. M., Hussain, Z., Shen, Z., Mo, S., Wong, E., Salmeron, M. B., Wang, F., Crommie, M. F., Ogletree, D., Neaton, J. B., Weber-Bargioni, A. 2016; 12 (8): 751–56

  View details for DOI 10.1038/NPHYS3730

  View details for Web of Science ID 000381239800014

• Quartz tuning fork based microwave impedance microscopy REVIEW OF SCIENTIFIC INSTRUMENTS Cui, Y., Ma, E. Y., Shen, Z. 2016; 87 (6)

  Abstract

  Microwave impedance microscopy (MIM), a near-field microwave scanning probe technique, has become a powerful tool to characterize local electrical responses in solid state samples. We present the design of a new type of MIM sensor based on quartz tuning fork and electrochemically etched thin metal wires. Due to a higher aspect ratio tip and integration with tuning fork, such design achieves comparable MIM performance and enables easy self-sensing topography feedback in situations where the conventional optical feedback mechanism is not available, thus is complementary to microfabricated shielded stripline-type probes. The new design also enables stable differential mode MIM detection and multiple-frequency MIM measurements with a single sensor.

  View details for DOI 10.1063/1.4954156

  View details for Web of Science ID 000379177000047

  View details for PubMedID 27370463

• Quantitative Theory for Probe-Sample Interaction With Inhomogeneous Perturbation in Near-Field Scanning Microwave Microscopy IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES Wei, Z., Cui, Y., Ma, E. Y., Johnston, S., Yang, Y., Chen, R., Kelly, M., Shen, Z., Chen, X. 2016; 64 (5): 1402-1408

  View details for DOI 10.1109/TMTT.2016.2537801

  View details for Web of Science ID 000380067700007

• Electronic Structure, Surface Doping, and Optical Response in Epitaxial WSe2 Thin Films. Nano letters Zhang, Y., Ugeda, M. M., Jin, C., Shi, S., Bradley, A. J., Martín-Recio, A., Ryu, H., Kim, J., Tang, S., Kim, Y., Zhou, B., Hwang, C., Chen, Y., Wang, F., Crommie, M. F., Hussain, Z., Shen, Z., Mo, S. 2016; 16 (4): 2485-2491

  Abstract

  High quality WSe2 films have been grown on bilayer graphene (BLG) with layer-by-layer control of thickness using molecular beam epitaxy. The combination of angle-resolved photoemission, scanning tunneling microscopy/spectroscopy, and optical absorption measurements reveal the atomic and electronic structures evolution and optical response of WSe2/BLG. We observe that a bilayer of WSe2 is a direct bandgap semiconductor, when integrated in a BLG-based heterostructure, thus shifting the direct-indirect band gap crossover to trilayer WSe2. In the monolayer limit, WSe2 shows a spin-splitting of 475 meV in the valence band at the K point, the largest value observed among all the MX2 (M = Mo, W; X = S, Se) materials. The exciton binding energy of monolayer-WSe2/BLG is found to be 0.21 eV, a value that is orders of magnitude larger than that of conventional three-dimensional semiconductors, yet small as compared to other two-dimensional transition metal dichalcogennides (TMDCs) semiconductors. Finally, our finding regarding the overall modification of the electronic structure by an alkali metal surface electron doping opens a route to further control the electronic properties of TMDCs.

  View details for DOI 10.1021/acs.nanolett.6b00059

  View details for PubMedID 26974978

• Ultralow effective work function surfaces using diamondoid monolayers. Nature nanotechnology Narasimha, K. T., Ge, C., Fabbri, J. D., Clay, W., Tkachenko, B. A., Fokin, A. A., Schreiner, P. R., Dahl, J. E., Carlson, R. M., Shen, Z. X., Melosh, N. A. 2016; 11 (3): 267-272

  Abstract

  Electron emission is critical for a host of modern fabrication and analysis applications including mass spectrometry, electron imaging and nanopatterning. Here, we report that monolayers of diamondoids effectively confer dramatically enhanced field emission properties to metal surfaces. We attribute the improved emission to a significant reduction of the work function rather than a geometric enhancement. This effect depends on the particular diamondoid isomer, with [121]tetramantane-2-thiol reducing gold's work function from ∼5.1 eV to 1.60 ± 0.3 eV, corresponding to an increase in current by a factor of over 13,000. This reduction in work function is the largest reported for any organic species and also the largest for any air-stable compound. This effect was not observed for sp(3)-hybridized alkanes, nor for smaller diamondoid molecules. The magnitude of the enhancement, molecule specificity and elimination of gold metal rearrangement precludes geometric factors as the dominant contribution. Instead, we attribute this effect to the stable radical cation of diamondoids. Our computed enhancement due to a positively charged radical cation was in agreement with the measured work functions to within ±0.3 eV, suggesting a new paradigm for low-work-function coatings based on the design of nanoparticles with stable radical cations.

  View details for DOI 10.1038/nnano.2015.277

  View details for PubMedID 26641529

• Ultrafast resonant soft x-ray diffraction dynamics of the charge density wave in TbTe3 PHYSICAL REVIEW B Moore, R. G., Lee, W. S., Kirchman, P. S., Chuang, Y. D., Kemper, A. F., Trigo, M., Patthey, L., Lu, D. H., Krupin, O., Yi, M., Reis, D. A., Doering, D., Denes, P., Schlotter, W. F., Turner, J. J., Hays, G., Hering, P., Benson, T., Chu, J., Devereaux, T. P., Fisher, I. R., Hussain, Z., Shen, Z. 2016; 93 (2)

  View details for DOI 10.1103/PhysRevB.93.024304

  View details for Web of Science ID 000369218500004

• Raman and fluorescence characteristics of resonant inelastic X-ray scattering from doped superconducting cuprates SCIENTIFIC REPORTS Huang, H. Y., Jia, C. J., Chen, Z. Y., Wohlfeld, K., Moritz, B., Devereaux, T. P., Wu, W. B., Okamoto, J., Lee, W. S., Hashimoto, M., He, Y., Shen, Z. X., Yoshida, Y., Eisaki, H., Mou, C. Y., Chen, C. T., Huang, D. J. 2016; 6

  Abstract

  Measurements of spin excitations are essential for an understanding of spin-mediated pairing for superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy spin excitations. However, whether RIXS correctly measures the collective spin excitations of doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- and fluorescence-like RIXS excitations of Bi1.5Pb0.6Sr1.54CaCu2O(8+δ). Combining photon-energy and momentum dependent RIXS measurements with theoretical calculations using exact diagonalization provides conclusive evidence that the Raman-like RIXS excitations correspond to collective spin excitations, which are magnons in the undoped Mott insulators and evolve into paramagnons in doped superconducting compounds. In contrast, the fluorescence-like shifts are due primarily to the continuum of particle-hole excitations in the charge channel. Our results show that under the proper experimental conditions RIXS indeed can be used to probe paramagnons in doped high-Tc cuprate superconductors.

  View details for DOI 10.1038/srep19657

  View details for Web of Science ID 000368667100002

  View details for PubMedCentralID PMC4726252

• Coexistence of a pseudogap and a superconducting gap for the high-T-c superconductor La2-xSrxCuO4 studied by angle-resolved photoemission spectroscopy PHYSICAL REVIEW B Yoshida, T., Malaeb, W., Ideta, S., Lu, D. H., Moor, R. G., Shen, Z., Okawa, M., Kiss, T., Ishizaka, K., Shin, S., Komiya, S., Ando, Y., Eisaki, H., Uchida, S., Fujimori, A. 2016; 93 (1)

  View details for DOI 10.1103/PhysRevB.93.014513

  View details for Web of Science ID 000368481300013

• Hybrid Group IV Nanophotonic Structures Incorporating Diamond Silicon-Vacancy Color Centers. Nano letters Zhang, J. L., Ishiwata, H., Babinec, T. M., Radulaski, M., Müller, K., Lagoudakis, K. G., Dory, C., Dahl, J., Edgington, R., Soulière, V., Ferro, G., Fokin, A. A., Schreiner, P. R., Shen, Z. X., Melosh, N. A., Vučković, J. 2016; 16 (1): 212-7

  Abstract

  We demonstrate a new approach for engineering group IV semiconductor-based quantum photonic structures containing negatively charged silicon-vacancy (SiV(-)) color centers in diamond as quantum emitters. Hybrid diamond-SiC structures are realized by combining the growth of nano- and microdiamonds on silicon carbide (3C or 4H polytype) substrates, with the subsequent use of these diamond crystals as a hard mask for pattern transfer. SiV(-) color centers are incorporated in diamond during its synthesis from molecular diamond seeds (diamondoids), with no need for ion-implantation or annealing. We show that the same growth technique can be used to grow a diamond layer controllably doped with SiV(-) on top of a high purity bulk diamond, in which we subsequently fabricate nanopillar arrays containing high quality SiV(-) centers. Scanning confocal photoluminescence measurements reveal optically active SiV(-) lines both at room temperature and low temperature (5 K) from all fabricated structures, and, in particular, very narrow line widths and small inhomogeneous broadening of SiV(-) lines from all-diamond nanopillar arrays, which is a critical requirement for quantum computation. At low temperatures (5 K) we observe in these structures the signature typical of SiV(-) centers in bulk diamond, consistent with a double lambda. These results indicate that high quality color centers can be incorporated into nanophotonic structures synthetically with properties equivalent to those in bulk diamond, thereby opening opportunities for applications in classical and quantum information processing.

  View details for DOI 10.1021/acs.nanolett.5b03515

  View details for PubMedID 26695059

• Hybrid Group IV Nanophotonic Structures Incorporating Diamond Silicon-Vacancy Color Centers NANO LETTERS Zhang, J. L., Ishiwata, H., Babinec, T. M., Radulaski, M., Mueller, K., Lagoudakis, K. G., Dory, C., Dahl, J., Edgington, R., Souliere, V., Ferro, G., Fokin, A. A., Schreiner, P. R., Shen, Z., Melosh, N. A., Vuckovic, J. 2016; 16 (1): 212-217

  Abstract

  We demonstrate a new approach for engineering group IV semiconductor-based quantum photonic structures containing negatively charged silicon-vacancy (SiV(-)) color centers in diamond as quantum emitters. Hybrid diamond-SiC structures are realized by combining the growth of nano- and microdiamonds on silicon carbide (3C or 4H polytype) substrates, with the subsequent use of these diamond crystals as a hard mask for pattern transfer. SiV(-) color centers are incorporated in diamond during its synthesis from molecular diamond seeds (diamondoids), with no need for ion-implantation or annealing. We show that the same growth technique can be used to grow a diamond layer controllably doped with SiV(-) on top of a high purity bulk diamond, in which we subsequently fabricate nanopillar arrays containing high quality SiV(-) centers. Scanning confocal photoluminescence measurements reveal optically active SiV(-) lines both at room temperature and low temperature (5 K) from all fabricated structures, and, in particular, very narrow line widths and small inhomogeneous broadening of SiV(-) lines from all-diamond nanopillar arrays, which is a critical requirement for quantum computation. At low temperatures (5 K) we observe in these structures the signature typical of SiV(-) centers in bulk diamond, consistent with a double lambda. These results indicate that high quality color centers can be incorporated into nanophotonic structures synthetically with properties equivalent to those in bulk diamond, thereby opening opportunities for applications in classical and quantum information processing.

  View details for DOI 10.1021/acs.nanolett.5b03515

  View details for Web of Science ID 000368322700034

• Atomically-Thin HfSe2 Transistors with Native Metal Oxides Mleczko, M. J., Zhang, C., Lee, H., Kuo, H., Magyari-Kope, B., Shen, Z., Moore, R. G., Fisher, I. R., Nishi, Y., Pop, E., IEEE IEEE. 2016

  View details for Web of Science ID 000389535400076

• Emitter-Cavity Coupling in Hybrid Silicon Carbide-Nanodiamond Microdisk Resonators Radulaski, M., Tzeng, Y., Zhang, J., Ishiwata, H., Lagoudakis, K. G., Souliere, V., Ferro, G., Shen, Z., Melosh, N. A., Chu, S., Vuckovic, J., IEEE IEEE. 2016

  View details for Web of Science ID 000391286402328

• Low Strain Silicon-Vacancy Color Centers in Diamond Nanopillar Arrays Zhang, J., Ishiwata, H., Babinec, T. M., Radulaski, M., Muller, K., Lagoudakis, K. G., Dory, C., Shen, Z., Melosh, N. A., Vuckovic, J., IEEE IEEE. 2016

  View details for Web of Science ID 000391286402321

• Invited Article: High resolution angle resolved photoemission with tabletop 11 eV laser. Review of scientific instruments He, Y., Vishik, I. M., Yi, M., Yang, S., Liu, Z., Lee, J. J., Chen, S., Rebec, S. N., Leuenberger, D., Zong, A., Jefferson, C. M., Moore, R. G., Kirchmann, P. S., Merriam, A. J., Shen, Z. 2016; 87 (1): 011301-?

  Abstract

  We developed a table-top vacuum ultraviolet (VUV) laser with 113.778 nm wavelength (10.897 eV) and demonstrated its viability as a photon source for high resolution angle-resolved photoemission spectroscopy (ARPES). This sub-nanosecond pulsed VUV laser operates at a repetition rate of 10 MHz, provides a flux of 2 × 10(12) photons/s, and enables photoemission with energy and momentum resolutions better than 2 meV and 0.012 Å(-1), respectively. Space-charge induced energy shifts and spectral broadenings can be reduced below 2 meV. The setup reaches electron momenta up to 1.2 Å(-1), granting full access to the first Brillouin zone of most materials. Control over the linear polarization, repetition rate, and photon flux of the VUV source facilitates ARPES investigations of a broad range of quantum materials, bridging the application gap between contemporary low energy laser-based ARPES and synchrotron-based ARPES. We describe the principles and operational characteristics of this source and showcase its performance for rare earth metal tritellurides, high temperature cuprate superconductors, and iron-based superconductors.

  View details for DOI 10.1063/1.4939759

  View details for PubMedID 26827301

• Origin of the low critical observing temperature of the quantum anomalous Hall effect in V-doped (Bi, Sb)2Te3 film. Scientific reports Li, W., Claassen, M., Chang, C., Moritz, B., Jia, T., Zhang, C., Rebec, S., Lee, J. J., Hashimoto, M., Lu, D., Moore, R. G., Moodera, J. S., Devereaux, T. P., Shen, Z. 2016; 6: 32732-?

  Abstract

  The experimental realization of the quantum anomalous Hall (QAH) effect in magnetically-doped (Bi, Sb)2Te3 films stands out as a landmark of modern condensed matter physics. However, ultra-low temperatures down to few tens of mK are needed to reach the quantization of Hall resistance, which is two orders of magnitude lower than the ferromagnetic phase transition temperature of the films. Here, we systematically study the band structure of V-doped (Bi, Sb)2Te3 thin films by angle-resolved photoemission spectroscopy (ARPES) and show unambiguously that the bulk valence band (BVB) maximum lies higher in energy than the surface state Dirac point. Our results demonstrate clear evidence that localization of BVB carriers plays an active role and can account for the temperature discrepancy.

  View details for DOI 10.1038/srep32732

  View details for PubMedID 27599406

• Persistent order due to transiently enhanced nesting in an electronically excited charge density wave. Nature communications Rettig, L., Cortés, R., Chu, J., Fisher, I. R., Schmitt, F., Moore, R. G., Shen, Z., Kirchmann, P. S., Wolf, M., Bovensiepen, U. 2016; 7: 10459-?

  Abstract

  Non-equilibrium conditions may lead to novel properties of materials with broken symmetry ground states not accessible in equilibrium as vividly demonstrated by non-linearly driven mid-infrared active phonon excitation. Potential energy surfaces of electronically excited states also allow to direct nuclear motion, but relaxation of the excess energy typically excites fluctuations leading to a reduced or even vanishing order parameter as characterized by an electronic energy gap. Here, using femtosecond time- and angle-resolved photoemission spectroscopy, we demonstrate a tendency towards transient stabilization of a charge density wave after near-infrared excitation, counteracting the suppression of order in the non-equilibrium state. Analysis of the dynamic electronic structure reveals a remaining energy gap in a highly excited transient state. Our observation can be explained by a competition between fluctuations in the electronically excited state, which tend to reduce order, and transiently enhanced Fermi surface nesting stabilizing the order.

  View details for DOI 10.1038/ncomms10459

  View details for PubMedID 26804717

  View details for PubMedCentralID PMC4737756

• Characterization of collective ground states in single-layer NbSe2 NATURE PHYSICS Ugeda, M. M., Bradley, A. J., Zhang, Y., Onishi, S., Chen, Y., Ruan, W., Ojeda-Aristizabal, C., Ryu, H., Edmonds, M. T., Tsai, H., Riss, A., Mo, S., Lee, D., Zettl, A., Hussain, Z., Shen, Z., Crommie, M. F. 2016; 12 (1): 92-U126

  View details for DOI 10.1038/NPHYS3527

  View details for Web of Science ID 000367835400026

• Direct Imaging of Dynamic Glassy Behavior in a Strained Manganite Film. Physical review letters Kundhikanjana, W., Sheng, Z., Yang, Y., Lai, K., Ma, E. Y., Cui, Y. T., Kelly, M. A., Nakamura, M., Kawasaki, M., Tokura, Y., Tang, Q., Zhang, K., Li, X., Shen, Z. X. 2015; 115 (26): 265701

  Abstract

  Complex many-body interaction in perovskite manganites gives rise to a strong competition between ferromagnetic metallic and charge-ordered phases with nanoscale electronic inhomogeneity and glassy behaviors. Investigating this glassy state requires high-resolution imaging techniques with sufficient sensitivity and stability. Here, we present the results of a near-field microwave microscope imaging on the strain-driven glassy state in a manganite film. The high contrast between the two electrically distinct phases allows direct visualization of the phase separation. The low-temperature microscopic configurations differ upon cooling with different thermal histories. At sufficiently high temperatures, we observe switching between the two phases in either direction. The dynamic switching, however, stops below the glass transition temperature. Compared with the magnetization data, the phase separation was microscopically frozen, while spin relaxation was found in a short period of time.

  View details for DOI 10.1103/PhysRevLett.115.265701

  View details for PubMedID 26765006

• Direct Imaging of Dynamic Glassy Behavior in a Strained Manganite Film PHYSICAL REVIEW LETTERS Kundhikanjana, W., Sheng, Z., Yang, Y., Lai, K., Ma, E. Y., Cui, Y., Kelly, M. A., Nakamura, M., Kawasaki, M., Tokura, Y., Tang, Q., Zhang, K., Li, X., Shen, Z. 2015; 115 (26)

  Abstract

  Complex many-body interaction in perovskite manganites gives rise to a strong competition between ferromagnetic metallic and charge-ordered phases with nanoscale electronic inhomogeneity and glassy behaviors. Investigating this glassy state requires high-resolution imaging techniques with sufficient sensitivity and stability. Here, we present the results of a near-field microwave microscope imaging on the strain-driven glassy state in a manganite film. The high contrast between the two electrically distinct phases allows direct visualization of the phase separation. The low-temperature microscopic configurations differ upon cooling with different thermal histories. At sufficiently high temperatures, we observe switching between the two phases in either direction. The dynamic switching, however, stops below the glass transition temperature. Compared with the magnetization data, the phase separation was microscopically frozen, while spin relaxation was found in a short period of time.

  View details for DOI 10.1103/PhysRevLett.115.265701

  View details for Web of Science ID 000367049000012

• Experimental observation of incoherent-coherent crossover and orbital-dependent band renormalization in iron chalcogenide superconductors PHYSICAL REVIEW B Liu, Z. K., Yi, M., Zhang, Y., Hu, J., Yu, R., Zhu, J., He, R., Chen, Y. L., Hashimoto, M., Moore, R. G., Mo, S., Hussain, Z., Si, Q., Mao, Z. Q., Lu, D. H., Shen, Z. 2015; 92 (23)

  View details for DOI 10.1103/PhysRevB.92.235138

  View details for Web of Science ID 000367064100001

• Bandwidth and Electron Correlation-Tuned Superconductivity in Rb0.8Fe2(Se1-zSz)(2) PHYSICAL REVIEW LETTERS Yi, M., Wang, M., Kemper, A. F., Mo, S., Hussain, Z., Bourret-Courchesne, E., Lanzara, A., Hashimoto, M., Lu, D. H., Shen, Z., Birgeneau, R. J. 2015; 115 (25)

  Abstract

  We present a systematic angle-resolved photoemission spectroscopy study of the substitution dependence of the electronic structure of Rb_{0.8}Fe_{2}(Se_{1-z}S_{z})_{2} (z=0, 0.5, 1), where superconductivity is continuously suppressed into a metallic phase. Going from the nonsuperconducting Rb_{0.8}Fe_{2}S_{2} to superconducting Rb_{0.8}Fe_{2}Se_{2}, we observe little change of the Fermi surface topology, but a reduction of the overall bandwidth by a factor of 2. Hence, for these heavily electron-doped iron chalcogenides, we have identified electron correlation as explicitly manifested in the quasiparticle bandwidth to be the important tuning parameter for superconductivity, and that moderate correlation is essential to achieving high T_{C}.

  View details for DOI 10.1103/PhysRevLett.115.256403

  View details for Web of Science ID 000366484900007

  View details for PubMedID 26722933

• Three-dimensional charge density wave order in YBa2Cu3O6.67 at high magnetic fields SCIENCE Gerber, S., Jang, H., Nojiri, H., Matsuzawa, S., Yasumura, H., Bonn, D. A., Liang, R., Hardy, W. N., Islam, Z., Mehta, A., Song, S., Sikorski, M., Stefanescu, D., Feng, Y., Kivelson, S. A., Devereaux, T. P., Shen, Z., Kao, C., Lee, W., Zhu, D., Lee, J. 2015; 350 (6263): 949-952

  Abstract

  Charge density wave (CDW) correlations have been shown to universally exist in cuprate superconductors. However, their nature at high fields inferred from nuclear magnetic resonance is distinct from that measured with x-ray scattering at zero and low fields. We combined a pulsed magnet with an x-ray free-electron laser to characterize the CDW in YBa2Cu3O6.67 via x-ray scattering in fields of up to 28 tesla. While the zero-field CDW order, which develops at temperatures below ~150 kelvin, is essentially two dimensional, at lower temperature and beyond 15 tesla, another three-dimensionally ordered CDW emerges. The field-induced CDW appears around the zero-field superconducting transition temperature; in contrast, the incommensurate in-plane ordering vector is field-independent. This implies that the two forms of CDW and high-temperature superconductivity are intimately linked.

  View details for DOI 10.1126/science.aac6257

  View details for Web of Science ID 000364955200042

  View details for PubMedID 26541608

• Mobile metallic domain walls in an all-in-all-out magnetic insulator SCIENCE Ma, E. Y., Cui, Y., Ueda, K., Tang, S., Chen, K., Tamura, N., Wu, P. M., Fujioka, J., Tokura, Y., Shen, Z. 2015; 350 (6260): 538-541

  Abstract

  Magnetic domain walls are boundaries between regions with different configurations of the same magnetic order. In a magnetic insulator, where the magnetic order is tied to its bulk insulating property, it has been postulated that electrical properties are drastically different along the domain walls, where the order is inevitably disturbed. Here we report the discovery of highly conductive magnetic domain walls in a magnetic insulator, Nd2Ir2O7, that has an unusual all-in-all-out magnetic order, via transport and spatially resolved microwave impedance microscopy. The domain walls have a virtually temperature-independent sheet resistance of ~1 kilohm per square, show smooth morphology with no preferred orientation, are free from pinning by disorders, and have strong thermal and magnetic field responses that agree with expectations for all-in-all-out magnetic order.

  View details for DOI 10.1126/science.aac8289

  View details for Web of Science ID 000363660000043

  View details for PubMedID 26516280

• Engineering Ultra-Low Work Function of Graphene NANO LETTERS Yuan, H., Chang, S., Bargatin, I., Wang, N. C., Riley, D. C., Wang, H., Schwede, J. W., Provine, J., Pop, E., Shen, Z., Pianetta, P. A., Melosh, N. A., Howe, R. T. 2015; 15 (10): 6475-6480

  Abstract

  Low work function materials are critical for energy conversion and electron emission applications. Here, we demonstrate for the first time that an ultralow work function graphene is achieved by combining electrostatic gating with a Cs/O surface coating. A simple device is built from large-area monolayer graphene grown by chemical vapor deposition, transferred onto 20 nm HfO2 on Si, enabling high electric fields capacitive charge accumulation in the graphene. We first observed over 0.7 eV work function change due to electrostatic gating as measured by scanning Kelvin probe force microscopy and confirmed by conductivity measurements. The deposition of Cs/O further reduced the work function, as measured by photoemission in an ultrahigh vacuum environment, which reaches nearly 1 eV, the lowest reported to date for a conductive, nondiamond material.

  View details for DOI 10.1021/acs.nanolett.5b01916

  View details for PubMedID 26401728

• Mott localization in a pure stripe antiferromagnet Rb1-delta Fe1.5-sigma S2 PHYSICAL REVIEW B Wang, M., Yi, M., Cao, H., De La Cruz, C., Mo, S. K., Huang, Q. Z., Bourret-Courchesne, E., Dai, P., Lee, D. H., Shen, Z. X., Birgeneau, R. J. 2015; 92 (12)

  View details for DOI 10.1103/PhysRevB.92.121101

  View details for Web of Science ID 000360331600001

• Magnetic excitations and phonons simultaneously studied by resonant inelastic x-ray scattering in optimally doped Bi1.5Pb0.55Sr1.6La0.4CuO6+delta PHYSICAL REVIEW B Peng, Y. Y., Hashimoto, M., Sala, M. M., AMORESE, A., Brookes, N. B., Dellea, G., Lee, W., Minola, M., Schmitt, T., Yoshida, Y., Zhou, K., Eisaki, H., Devereaux, T. P., Shen, Z., Braicovich, L., Ghiringhelli, G. 2015; 92 (6)

  View details for DOI 10.1103/PhysRevB.92.064517

  View details for Web of Science ID 000362212200011

• Electron-phonon coupling in a system with broken symmetry: Surface of Be(0001) PHYSICAL REVIEW B Chien, T., He, X., Mo, S., Hashimoto, M., Hussain, Z., Shen, Z., Plummer, E. W. 2015; 92 (7)

  View details for DOI 10.1103/PhysRevB.92.075133

  View details for Web of Science ID 000359860100002

• Thermionic and photon-enhanced emission energy conversion Melosh, N., Riley, D., Sahasrabuddhe, K., Shen, Z. X., Schwede, J., Howe, R. AMER CHEMICAL SOC. 2015

  View details for Web of Science ID 000432475703009

• Polarization-sensitive broadband photodetector using a black phosphorus vertical p-n junction NATURE NANOTECHNOLOGY Yuan, H., Liu, X., Afshinmanesh, F., Li, W., Xu, G., Sun, J., Lian, B., Curto, A. G., Ye, G., Hikita, Y., Shen, Z., Zhang, S., Chen, X., Brongersma, M., Hwang, H. Y., Cui, Y. 2015; 10 (8): 707-713

  Abstract

  The ability to detect light over a broad spectral range is central to practical optoelectronic applications and has been successfully demonstrated with photodetectors of two-dimensional layered crystals such as graphene and MoS2. However, polarization sensitivity within such a photodetector remains elusive. Here, we demonstrate a broadband photodetector using a layered black phosphorus transistor that is polarization-sensitive over a bandwidth from ∼400 nm to 3,750 nm. The polarization sensitivity is due to the strong intrinsic linear dichroism, which arises from the in-plane optical anisotropy of this material. In this transistor geometry, a perpendicular built-in electric field induced by gating can spatially separate the photogenerated electrons and holes in the channel, effectively reducing their recombination rate and thus enhancing the performance for linear dichroism photodetection. The use of anisotropic layered black phosphorus in polarization-sensitive photodetection might provide new functionalities in novel optical and optoelectronic device applications.

  View details for DOI 10.1038/NNANO.2015.112

  View details for PubMedID 26030655

• Dependence of electron correlation strength in Fe1+yTe1-xSex on Se content PHYSICAL REVIEW B Ambolode, L. C., Okazaki, K., Horio, M., Suzuki, H., Liu, L., Ideta, S., Yoshida, T., Mikami, T., Kakeshita, T., Uchida, S., Ono, K., Kumigashira, H., Hashimoto, M., Lu, D., Shen, Z., Fujimori, A. 2015; 92 (3)

  View details for DOI 10.1103/PhysRevB.92.035104

  View details for Web of Science ID 000357261300003

• Charge-order domain walls with enhanced conductivity in a layered manganite NATURE COMMUNICATIONS Ma, E. Y., Bryant, B., Tokunaga, Y., Aeppli, G., Tokura, Y., Shen, Z. 2015; 6

  Abstract

  Interfaces and boundaries in condensed-matter systems often have electronic properties distinct from the bulk material and thus have become a topic of both fundamental scientific interest and technological importance. Here we identify, using microwave impedance microscopy, enhanced conductivity of charge-order domain walls in the layered manganite Pr(Sr0.1Ca0.9)2Mn2O7. We obtain a complete mesoscopic map of surface topography, crystalline orientation and electronic phase, and visualize the thermal phase transition between two charge-ordered phases. In both phases, charge-order domains occur with domain walls showing enhanced conductivity likely due to local lifting of the charge order. Finite element analysis shows that the resolved domain walls can be as narrow as few nanometres. The domain walls are stabilized by structural twins and have a strong history dependence, suggesting that they may be manipulated to create novel devices.

  View details for DOI 10.1038/ncomms8595

  View details for Web of Science ID 000358856100002

  View details for PubMedCentralID PMC4506533

• Inequivalence of Single-Particle and Population Lifetimes in a Cuprate Superconductor PHYSICAL REVIEW LETTERS Yang, S., Sobota, J. A., Leuenberger, D., He, Y., Hashimoto, M., Lu, D. H., Eisaki, H., Kirchmann, P. S., Shen, Z. 2015; 114 (24)

  Abstract

  We study optimally doped Bi-2212 (T(c)=96  K) using femtosecond time- and angle-resolved photoelectron spectroscopy. Energy-resolved population lifetimes are extracted and compared with single-particle lifetimes measured by equilibrium photoemission. The population lifetimes deviate from the single-particle lifetimes in the low excitation limit by 1-2 orders of magnitude. Fundamental considerations of electron scattering unveil that these two lifetimes are in general distinct, yet for systems with only electron-phonon scattering they should converge in the low-temperature, low-fluence limit. The qualitative disparity in our data, even in this limit, suggests that scattering channels beyond electron-phonon interactions play a significant role in the electron dynamics of cuprate superconductors.

  View details for DOI 10.1103/PhysRevLett.114.247001

  View details for Web of Science ID 000356132700010

• Thickness-Dependent Coherent Phonon Frequency in Ultrathin FeSe/SrTiO3 Films NANO LETTERS Yang, S., Sobota, J. A., Leuenberger, D., Kemper, A. F., Lee, J. J., Schmitt, F. T., Li, W., Moore, R. G., Kirchmann, P. S., Shen, Z. 2015; 15 (6): 4150-4154

  Abstract

  Ultrathin FeSe films grown on SrTiO3 substrates are a recent milestone in atomic material engineering due to their important role in understanding unconventional superconductivity in Fe-based materials. By using femtosecond time- and angle-resolved photoelectron spectroscopy, we study phonon frequencies in ultrathin FeSe/SrTiO3 films grown by molecular beam epitaxy. After optical excitation, we observe periodic modulations of the photoelectron spectrum as a function of pump-probe delay for 1-unit-cell, 3-unit-cell, and 60-unit-cell thick FeSe films. The frequencies of the coherent intensity oscillations increase from 5.00 ± 0.02 to 5.25 ± 0.02 THz with increasing film thickness. By comparing with previous works, we attribute this mode to the Se A1g phonon. The dominant mechanism for the phonon softening in 1-unit-cell thick FeSe films is a substrate-induced lattice strain. Our results demonstrate an abrupt phonon renormalization due to a lattice mismatch between the ultrathin film and the substrate.

  View details for DOI 10.1021/acs.nanolett.5b01274

  View details for Web of Science ID 000356316900074

  View details for PubMedID 26027951

• Direct characterization of photoinduced lattice dynamics in BaFe2As2 NATURE COMMUNICATIONS Gerber, S., Kim, K. W., Zhang, Y., Zhu, D., Plonka, N., Yi, M., Dakovski, G. L., Leuenberger, D., Kirchmann, P. S., Moore, R. G., Chollet, M., Glownia, J. M., Feng, Y., Lee, J., Mehta, A., Kemper, A. F., Wolf, T., Chuang, Y., Hussain, Z., Kao, C., Moritz, B., Shen, Z., Devereaux, T. P., Lee, W. 2015; 6

  Abstract

  Ultrafast light pulses can modify electronic properties of quantum materials by perturbing the underlying, intertwined degrees of freedom. In particular, iron-based superconductors exhibit a strong coupling among electronic nematic fluctuations, spins and the lattice, serving as a playground for ultrafast manipulation. Here we use time-resolved X-ray scattering to measure the lattice dynamics of photoexcited BaFe2As2. On optical excitation, no signature of an ultrafast change of the crystal symmetry is observed, but the lattice oscillates rapidly in time due to the coherent excitation of an A1g mode that modulates the Fe-As-Fe bond angle. We directly quantify the coherent lattice dynamics and show that even a small photoinduced lattice distortion can induce notable changes in the electronic and magnetic properties. Our analysis implies that transient structural modification can be an effective tool for manipulating the electronic properties of multi-orbital systems, where electronic instabilities are sensitive to the orbital character of bands.

  View details for DOI 10.1038/ncomms8377

  View details for Web of Science ID 000357175300010

  View details for PubMedID 26051704

  View details for PubMedCentralID PMC4468847

• Classification of collective modes in a charge density wave by momentum-dependent modulation of the electronic band structure PHYSICAL REVIEW B Leuenberger, D., Sobota, J. A., Yang, S., Kemper, A. F., Giraldo-Gallo, P., Moore, R. G., Fisher, I. R., Kirchmann, P. S., Devereaux, T. P., Shen, Z. 2015; 91 (20)

  View details for DOI 10.1103/PhysRevB.91.201106

  View details for Web of Science ID 000354985300001

• Unexpected edge conduction in mercury telluride quantum wells under broken time-reversal symmetry NATURE COMMUNICATIONS Ma, E. Y., Calvo, M. R., Wang, J., Lian, B., Muehlbauer, M., Bruene, C., Cui, Y., Lai, K., Kundhikanjana, W., Yang, Y., Baenninger, M., Koenig, M., Ames, C., Buhmann, H., Leubner, P., Molenkamp, L. W., Zhang, S., Goldhaber-Gordon, D., Kelly, M. A., Shen, Z. 2015; 6

  Abstract

  The realization of quantum spin Hall effect in HgTe quantum wells is considered a milestone in the discovery of topological insulators. Quantum spin Hall states are predicted to allow current flow at the edges of an insulating bulk, as demonstrated in various experiments. A key prediction yet to be experimentally verified is the breakdown of the edge conduction under broken time-reversal symmetry. Here we first establish a systematic framework for the magnetic field dependence of electrostatically gated quantum spin Hall devices. We then study edge conduction of an inverted quantum well device under broken time-reversal symmetry using microwave impedance microscopy, and compare our findings to a non-inverted device. At zero magnetic field, only the inverted device shows clear edge conduction in its local conductivity profile, consistent with theory. Surprisingly, the edge conduction persists up to 9 T with little change. This indicates physics beyond simple quantum spin Hall model, including material-specific properties and possibly many-body effects.

  View details for DOI 10.1038/ncomms8252

  View details for Web of Science ID 000355539500001

  View details for PubMedID 26006728

  View details for PubMedCentralID PMC4455136

• Probing the Role of Interlayer Coupling and Coulomb Interactions on Electronic Structure in Few-Layer MoSe2 Nanostructures NANO LETTERS Bradley, A. J., Ugeda, M. M., da Jornada, F. H., Qiu, D. Y., Ruan, W., Zhang, Y., Wickenburg, S., Riss, A., Lu, J., Mo, S., Hussain, Z., Shen, Z., Louie, S. G., Crommie, M. F. 2015; 15 (4): 2594-2599

  Abstract

  Despite the weak nature of interlayer forces in transition metal dichalcogenide (TMD) materials, their properties are highly dependent on the number of layers in the few-layer two-dimensional (2D) limit. Here, we present a combined scanning tunneling microscopy/spectroscopy and GW theoretical study of the electronic structure of high quality single- and few-layer MoSe2 grown on bilayer graphene. We find that the electronic (quasiparticle) bandgap, a fundamental parameter for transport and optical phenomena, decreases by nearly one electronvolt when going from one layer to three due to interlayer coupling and screening effects. Our results paint a clear picture of the evolution of the electronic wave function hybridization in the valleys of both the valence and conduction bands as the number of layers is changed. This demonstrates the importance of layer number and electron-electron interactions on van der Waals heterostructures and helps to clarify how their electronic properties might be tuned in future 2D nanodevices.

  View details for DOI 10.1021/acs.nanolett.51300160

  View details for Web of Science ID 000352750200057

  View details for PubMedID 25775022

• Interface ferroelectric transition near the gap-opening temperature in a single-unit-cell FeSe film grown on Nb-Doped SrTiO3 substrate. Physical review letters Cui, Y., Moore, R. G., Zhang, A., Tian, Y., Lee, J. J., Schmitt, F. T., Zhang, W., Li, W., Yi, M., Liu, Z., Hashimoto, M., Zhang, Y., Lu, D., Devereaux, T. P., Wang, L., Ma, X., Zhang, Q., Xue, Q., Lee, D., Shen, Z. 2015; 114 (3): 037002-?

  Abstract

  We report findings of strong anomalies in both mutual inductance and inelastic Raman spectroscopy measurements of single-unit-cell FeSe film grown on Nb-doped SrTiO3, which occur near the temperature where the superconductinglike energy gap opens. Analysis suggests that the anomaly is associated with a broadened ferroelectric transition in a thin layer near the FeSe/SrTiO3 interface. The coincidence of the ferroelectric transition and gap-opening temperatures adds credence to the central role played by the film-substrate interaction on the strong Cooper pairing in this system. We discuss scenarios that could explain such a coincidence.

  View details for PubMedID 25659015

• Direct spectroscopic evidence for phase competition between the pseudogap and superconductivity in Bi2Sr2CaCu2O8+delta NATURE MATERIALS Hashimoto, M., Nowadnick, E. A., He, R., Vishik, I. M., Moritz, B., He, Y., Tanaka, K., Moore, R. G., Lu, D., Yoshida, Y., Ishikado, M., Sasagawa, T., Fujita, K., Ishida, S., Uchida, S., Eisaki, H., Hussain, Z., Devereaux, T. P., Shen, Z. 2015; 14 (1): 37-42

  Abstract

  In the high-temperature (Tc) cuprate superconductors, a growing body of evidence suggests that the pseudogap phase, existing below the pseudogap temperature T(∗), is characterized by some broken electronic symmetries distinct from those associated with superconductivity. In particular, recent scattering experiments have suggested that charge ordering competes with superconductivity. However, no direct link of an interplay between the two phases has been identified from the important low-energy excitations. Here, we report an antagonistic singularity at Tc in the spectral weight of Bi2Sr2CaCu2O8+δ as compelling evidence for phase competition, which persists up to a high hole concentration p ~ 0.22. Comparison with theoretical calculations confirms that the singularity is a signature of competition between the order parameters for the pseudogap and superconductivity. The observation of the spectroscopic singularity at finite temperatures over a wide doping range provides new insights into the nature of the competitive interplay between the two orders and the complex phase diagram near the pseudogap critical point.

  View details for DOI 10.1038/NMAT4116

  View details for Web of Science ID 000346430100011

  View details for PubMedID 25362356

• A tunable, linac based, intense, broad-band THz source forpump-probe experiments Schmerge, J., Adolphsen, C., Corbett, J., Dolgashev, V., Durr, H., Durr, M., Fazio, M., Fisher, A., Frisch, J., Gaffney, K., Guehr, M., Hastings, J., Hettel, B., Hoffmann, M., Hogan, M., Holtkamp, N., Huang, X., Huang, Z., Kirchmann, P., LaRue, J., Limborg, C., Lindenberg, A., Loos, H., Maxwell, T., Nilsson, A., et al U.S. Department of Energy, Office of Scientific and Technical Information. United States. 2015
• Fluorescent nanodiamonds from molecular diamond seed Hitoshi, H., Zhang, J., Edgington, R., Babinec, T., Muller, K., Lagoudakis, K., Melosh, N., Shen, Z., Vuckovic, J. CLEO: 2015, OSA Technical Digest (online) (Optical Society of America, 2015), paper FM2E.2.. San Jose, California. 2015
• Hybrid Diamond-Silicon Carbide Structures Incorporating Silicon-Vacancies in Diamond as Quantum Emitters Zhang, J., Ishiwata, H., Radulaski, M., Babinec, T. M., Mueller, K., Lagoudakis, K. G., Edgington, R., Alassaad, K., Ferro, G., Melosh, N. A., Shen, Z., Vuckovic, J., IEEE IEEE. 2015

  View details for Web of Science ID 000370627101430

• Charge-order domain walls with enhanced conductivity in a layered manganite. Nature communications Ma, E. Y., Bryant, B., Tokunaga, Y., Aeppli, G., Tokura, Y., Shen, Z. 2015; 6: 7595-?

  Abstract

  Interfaces and boundaries in condensed-matter systems often have electronic properties distinct from the bulk material and thus have become a topic of both fundamental scientific interest and technological importance. Here we identify, using microwave impedance microscopy, enhanced conductivity of charge-order domain walls in the layered manganite Pr(Sr0.1Ca0.9)2Mn2O7. We obtain a complete mesoscopic map of surface topography, crystalline orientation and electronic phase, and visualize the thermal phase transition between two charge-ordered phases. In both phases, charge-order domains occur with domain walls showing enhanced conductivity likely due to local lifting of the charge order. Finite element analysis shows that the resolved domain walls can be as narrow as few nanometres. The domain walls are stabilized by structural twins and have a strong history dependence, suggesting that they may be manipulated to create novel devices.

  View details for DOI 10.1038/ncomms8595

  View details for PubMedID 26139185

• Physical properties of materials derived from diamondoid molecules REPORTS ON PROGRESS IN PHYSICS Clay, W. A., Dahl, J. E., Carlson, R. M., Melosh, N. A., Shen, Z. 2015; 78 (1)

  View details for DOI 10.1088/0034-4885/78/1/016501

  View details for Web of Science ID 000348760600003

  View details for PubMedID 25551840

• Observation of universal strong orbital-dependent correlation effects in iron chalcogenides. Nature communications Yi, M., Liu, Z., Zhang, Y., Yu, R., Zhu, J., Lee, J. J., Moore, R. G., Schmitt, F. T., Li, W., Riggs, S. C., Chu, J., Lv, B., Hu, J., Hashimoto, M., Mo, S., Hussain, Z., Mao, Z. Q., Chu, C. W., Fisher, I. R., Si, Q., Shen, Z., Lu, D. H. 2015; 6: 7777-?

  View details for DOI 10.1038/ncomms8777

  View details for PubMedID 26204461

• Giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor NATURE MATERIALS Ugeda, M. M., Bradley, A. J., Shi, S., da Jornada, F. H., Zhang, Y., Qiu, D. Y., Ruan, W., Mo, S., Hussain, Z., Shen, Z., Wang, F., Louie, S. G., Crommie, M. F. 2014; 13 (12): 1091-1095

  Abstract

  Two-dimensional (2D) transition metal dichalcogenides (TMDs) are emerging as a new platform for exploring 2D semiconductor physics. Reduced screening in two dimensions results in markedly enhanced electron-electron interactions, which have been predicted to generate giant bandgap renormalization and excitonic effects. Here we present a rigorous experimental observation of extraordinarily large exciton binding energy in a 2D semiconducting TMD. We determine the single-particle electronic bandgap of single-layer MoSe2 by means of scanning tunnelling spectroscopy (STS), as well as the two-particle exciton transition energy using photoluminescence (PL) spectroscopy. These yield an exciton binding energy of 0.55 eV for monolayer MoSe2 on graphene—orders of magnitude larger than what is seen in conventional 3D semiconductors and significantly higher than what we see for MoSe2 monolayers in more highly screening environments. This finding is corroborated by our ab initio GW and Bethe-Salpeter equation calculations which include electron correlation effects. The renormalized bandgap and large exciton binding observed here will have a profound impact on electronic and optoelectronic device technologies based on single-layer semiconducting TMDs.

  View details for DOI 10.1038/NMAT4061

  View details for Web of Science ID 000345432200009

• Interfacial mode coupling as the origin of the enhancement of T-c in FeSe films on SrTiO3 NATURE Lee, J. J., Schmitt, F. T., Moore, R. G., Johnston, S., Cui, Y., Li, W., Yi, M., Liu, Z. K., Hashimoto, M., Zhang, Y., Lu, D. H., Devereaux, T. P., Lee, D., Shen, Z. 2014; 515 (7526): 245-U207

  Abstract

  Films of iron selenide (FeSe) one unit cell thick grown on strontium titanate (SrTiO3 or STO) substrates have recently shown superconducting energy gaps opening at temperatures close to the boiling point of liquid nitrogen (77 kelvin), which is a record for the iron-based superconductors. The gap opening temperature usually sets the superconducting transition temperature Tc, as the gap signals the formation of Cooper pairs, the bound electron states responsible for superconductivity. To understand why Cooper pairs form at such high temperatures, we examine the role of the SrTiO3 substrate. Here we report high-resolution angle-resolved photoemission spectroscopy results that reveal an unexpected characteristic of the single-unit-cell FeSe/SrTiO3 system: shake-off bands suggesting the presence of bosonic modes, most probably oxygen optical phonons in SrTiO3 (refs 5, 6, 7), which couple to the FeSe electrons with only a small momentum transfer. Such interfacial coupling assists superconductivity in most channels, including those mediated by spin fluctuations. Our calculations suggest that this coupling is responsible for raising the superconducting gap opening temperature in single-unit-cell FeSe/SrTiO3.

  View details for DOI 10.1038/nature13894

  View details for PubMedID 25391962

• Asymmetry of collective excitations in electron- and hole-doped cuprate superconductors NATURE PHYSICS Lee, W. S., Lee, J. J., Nowadnick, E. A., Gerber, S., Tabis, W., Huang, S. W., Strocov, V. N., Motoyama, E. M., Yu, G., Moritz, B., Huang, H. Y., Wang, R. P., Huang, Y. B., Wu, W. B., Chen, C. T., Huang, D. J., Greven, M., Schmitt, T., Shen, Z. X., Devereaux, T. P. 2014; 10 (11): 883-889

  View details for DOI 10.1038/NPHYS3117

  View details for Web of Science ID 000344846700024

• Distinguishing Bulk and Surface Electron-Phonon Coupling in the Topological Insulator Bi2Se3 Using Time-Resolved Photoemission Spectroscopy PHYSICAL REVIEW LETTERS Sobota, J. A., Yang, S., Leuenberger, D., Kemper, A. F., Analytis, J. G., Fisher, I. R., Kirchmann, P. S., Devereaux, T. P., Shen, Z. 2014; 113 (15)

  Abstract

  We report time- and angle-resolved photoemission spectroscopy measurements on the topological insulator Bi(2)Se(3). We observe oscillatory modulations of the electronic structure of both the bulk and surface states at a frequency of 2.23 THz due to coherent excitation of an A(1g) phonon mode. A distinct, additional frequency of 2.05 THz is observed in the surface state only. The lower phonon frequency at the surface is attributed to the termination of the crystal and thus reduction of interlayer van der Waals forces, which serve as restorative forces for out-of-plane lattice distortions. Density functional theory calculations quantitatively reproduce the magnitude of the surface phonon softening. These results represent the first band-resolved evidence of the A(1g) phonon mode coupling to the surface state in a topological insulator.

  View details for DOI 10.1103/PhysRevLett.113.157401

  View details for Web of Science ID 000344052200011

• Ultrafast electron dynamics in the topological insulator Bi2Se3 studied by time-resolved photoemission spectroscopy JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Sobota, J. A., Yang, S., Leuenberger, D., Kemper, A. F., Analytis, J. G., Fisher, I. R., Kirchmann, P. S., Devereaux, T. P., Shen, Z. 2014; 195: 249-257

  View details for DOI 10.1016/j.elspec.2014.01.005

  View details for Web of Science ID 000342872800036

• Molecular beam epitaxial growth of a three-dimensional topological Dirac semimetal Na3Bi APPLIED PHYSICS LETTERS Zhang, Y., Liu, Z., Zhou, B., Kim, Y., Hussain, Z., Shen, Z., Chen, Y., Mo, S. 2014; 105 (3)

  View details for DOI 10.1063/1.4890940

  View details for Web of Science ID 000341152300021

• Persistence of magnetic order in a highly excited Cu2+ state in CuO (vol 89, 220401, 2014) PHYSICAL REVIEW B Staub, U., de Souza, R. A., Beaud, P., Moehr-Vorobeva, E., Ingold, G., Caviezel, A., Scagnoli, V., Delley, B., Schlotter, W. F., Turner, J. J., Krupin, O., Lee, W., Chuang, Y., Patthey, L., Moore, R. G., Lu, D., Yi, M., Kirchmann, P. S., Trigo, M., Denes, P., Doering, D., Hussain, Z., Shen, Z. X., Prabhakaran, D., Boothroyd, A. T., Johnson, S. L. 2014; 90 (1)

  View details for DOI 10.1103/PhysRevB.90.019903

  View details for Web of Science ID 000339167200003

• Energy gaps in high-transition-temperature cuprate superconductors NATURE PHYSICS Hashimoto, M., Vishik, I. M., He, R., Devereaux, T. P., Shen, Z. 2014; 10 (7): 483-495

  View details for DOI 10.1038/NPHYS3009

  View details for Web of Science ID 000338843100014

• A stable three-dimensional topological Dirac semimetal Cd3As2 NATURE MATERIALS Liu, Z. K., Jiang, J., Zhou, B., Wang, Z. J., Zhang, Y., Weng, H. M., Prabhakaran, D., Mo, S., Peng, H., Dudin, P., Kim, T., Hoesch, M., Fang, Z., Dai, X., Shen, Z. X., Feng, D. L., Hussain, Z., Chen, Y. L. 2014; 13 (7): 677-681

  Abstract

  Three-dimensional (3D) topological Dirac semimetals (TDSs) are a recently proposed state of quantum matter that have attracted increasing attention in physics and materials science. A 3D TDS is not only a bulk analogue of graphene; it also exhibits non-trivial topology in its electronic structure that shares similarities with topological insulators. Moreover, a TDS can potentially be driven into other exotic phases (such as Weyl semimetals, axion insulators and topological superconductors), making it a unique parent compound for the study of these states and the phase transitions between them. Here, by performing angle-resolved photoemission spectroscopy, we directly observe a pair of 3D Dirac fermions in Cd3As2, proving that it is a model 3D TDS. Compared with other 3D TDSs, for example, β-cristobalite BiO2 (ref. 3) and Na3Bi (refs 4, 5), Cd3As2 is stable and has much higher Fermi velocities. Furthermore, by in situ doping we have been able to tune its Fermi energy, making it a flexible platform for exploring exotic physical phenomena.

  View details for DOI 10.1038/NMAT3990

  View details for Web of Science ID 000338482300013

  View details for PubMedID 24859642

• Electron propagation from a photo-excited surface: implications for time-resolved photoemission APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING Yang, S., Sobota, J. A., Kirchmann, P. S., Shen, Z. 2014; 116 (1): 85-90

  View details for DOI 10.1007/s00339-013-8154-9

  View details for Web of Science ID 000338214300012

• Direct observation of bulk charge modulations in optimally doped Bi1.5Pb0.6Sr1.54CaCu2O8+delta PHYSICAL REVIEW B Hashimoto, M., Ghiringhelli, G., Lee, W., Dellea, G., AMORESE, A., Mazzoli, C., KUMMER, K., Brookes, N. B., Moritz, B., Yoshida, Y., Eisaki, H., Hussain, Z., Devereaux, T. P., Shen, Z., Braicovich, L. 2014; 89 (22)

  View details for DOI 10.1103/PhysRevB.89.220511

  View details for Web of Science ID 000339049000001

• Persistence of magnetic order in a highly excited Cu2+ state in CuO PHYSICAL REVIEW B Staub, U., de Souza, R. A., Beaud, P., Moehr-Vorobeva, E., Ingold, G., Caviezel, A., Scagnoli, V., Delley, B., Turner, J. J., Krupin, O., Lee, W., Chuang, Y., Patthey, L., Moore, R. G., Lu, D., Yi, M., Kirchmann, P. S., Trigo, M., Denes, P., Doering, D., Hussain, Z., Shen, Z. X., Prabhakaran, D., Boothroyd, A. T., Johnson, S. L. 2014; 89 (22)

  View details for DOI 10.1103/PhysRevB.89.220401

  View details for Web of Science ID 000337274400001

• Strongly three-dimensional electronic structure and Fermi surfaces of SrFe2(As0.65P0.35)(2): Comparison with BaFe2(As1-xPx)(2) PHYSICAL REVIEW B Suzuki, H., Kobayashi, T., Miyasaka, S., Yoshida, T., Okazaki, K., Ambolode, L. C., Ideta, S., Yi, M., Hashimoto, M., Lu, D. H., Shen, Z., Ono, K., Kumigashira, H., Tajima, S., Fujimori, A. 2014; 89 (18)

  View details for DOI 10.1103/PhysRevB.89.184513

  View details for Web of Science ID 000338039000009

• Angle-resolved photoemission spectroscopy study of HgBa2CuO4+delta PHYSICAL REVIEW B Vishik, I. M., Barisic, N., Chan, M. K., Li, Y., Xia, D. D., Yu, G., Zhao, X., Lee, W. S., Meevasana, W., Devereaux, T. P., Greven, M., Shen, Z. 2014; 89 (19)

  View details for DOI 10.1103/PhysRevB.89.195141

  View details for Web of Science ID 000336841000003

• Electronic structure of BaNi2P2 observed by angle-resolved photoemission spectroscopy PHYSICAL REVIEW B Ideta, S., Yoshida, T., Nakajima, M., Malaeb, W., Kito, H., Eisaki, H., Iyo, A., Tomioka, Y., Ito, T., Kihou, K., Lee, C. H., Kotani, Y., Ono, K., Mo, S. K., Hussain, Z., Shen, Z., Harima, H., Uchida, S., Fujimori, A. 2014; 89 (19)

  View details for DOI 10.1103/PhysRevB.89.195138

  View details for Web of Science ID 000336755200003

• Shielded piezoresistive cantilever probes for nanoscale topography and electrical imaging JOURNAL OF MICROMECHANICS AND MICROENGINEERING Yang, Y., Ma, E. Y., Cui, Y., Haemmerli, A., Lai, K., Kundhikanjana, W., Harjee, N., Pruitt, B. L., Kelly, M., Shen, Z. 2014; 24 (4)

  View details for DOI 10.1088/0960-1317/24/4/045026

  View details for Web of Science ID 000334306100025

• Dynamic competition between spin-density wave order and superconductivity in underdoped Ba1-xKxFe2As2 NATURE COMMUNICATIONS Yi, M., Zhang, Y., Liu, Z., Ding, X., Chu, J., Kemper, A. F., Plonka, N., Moritz, B., Hashimoto, M., Mo, S., Hussain, Z., Devereaux, T. P., Fisher, I. R., Wen, H. H., Shen, Z., Lu, D. H. 2014; 5

  View details for DOI 10.1038/ncomms4711

  View details for Web of Science ID 000335223100002

  View details for PubMedID 24762657

• Superconducting graphene sheets in CaC6 enabled by phonon-mediated interband interactions NATURE COMMUNICATIONS Yang, S., Sobota, J. A., Howard, C. A., Pickard, C. J., Hashimoto, M., Lu, D. H., Mo, S., Kirchmann, P. S., Shen, Z. 2014; 5

  Abstract

  There is a great deal of fundamental and practical interest in the possibility of inducing superconductivity in a monolayer of graphene. But while bulk graphite can be made to superconduct when certain metal atoms are intercalated between its graphene sheets, the same has not been achieved in a single layer. Moreover, there is a considerable debate about the precise mechanism of superconductivity in intercalated graphite. Here we report angle-resolved photoelectron spectroscopy measurements of the superconducting graphite intercalation compound CaC6 that distinctly resolve both its intercalant-derived interlayer band and its graphene-derived π* band. Our results indicate the opening of a superconducting gap in the π* band and reveal a substantial contribution to the total electron-phonon-coupling strength from the π*-interlayer interband interaction. Combined with theoretical predictions, these results provide a complete account for the superconducting mechanism in graphite intercalation compounds and lend support to the idea of realizing superconducting graphene by creating an adatom superlattice.

  View details for DOI 10.1038/ncomms4493

  View details for Web of Science ID 000334301700004

  View details for PubMedID 24651261

  View details for PubMedCentralID PMC3973042

• Discovery of a Three-Dimensional Topological Dirac Semimetal, Na3Bi SCIENCE Liu, Z. K., Zhou, B., Zhang, Y., Wang, Z. J., Weng, H. M., Prabhakaran, D., Mo, S., Shen, Z. X., Fang, Z., Dai, X., Hussain, Z., Chen, Y. L. 2014; 343 (6173): 864-867

  Abstract

  Three-dimensional (3D) topological Dirac semimetals (TDSs) represent an unusual state of quantum matter that can be viewed as "3D graphene." In contrast to 2D Dirac fermions in graphene or on the surface of 3D topological insulators, TDSs possess 3D Dirac fermions in the bulk. By investigating the electronic structure of Na3Bi with angle-resolved photoemission spectroscopy, we detected 3D Dirac fermions with linear dispersions along all momentum directions. Furthermore, we demonstrated the robustness of 3D Dirac fermions in Na3Bi against in situ surface doping. Our results establish Na3Bi as a model system for 3D TDSs, which can serve as an ideal platform for the systematic study of quantum phase transitions between rich topological quantum states.

  View details for DOI 10.1126/science.1245085

  View details for Web of Science ID 000331552600040

  View details for PubMedID 24436183

• Direct observation of the transition from indirect to direct bandgap in atomically thin epitaxial MoSe2. Nature nanotechnology Zhang, Y., Chang, T., Zhou, B., Cui, Y., Yan, H., Liu, Z., Schmitt, F., Lee, J., Moore, R., Chen, Y., Lin, H., Jeng, H., Mo, S., Hussain, Z., Bansil, A., Shen, Z. 2014; 9 (2): 111-115

  Abstract

  Quantum systems in confined geometries are host to novel physical phenomena. Examples include quantum Hall systems in semiconductors and Dirac electrons in graphene. Interest in such systems has also been intensified by the recent discovery of a large enhancement in photoluminescence quantum efficiency and a potential route to valleytronics in atomically thin layers of transition metal dichalcogenides, MX2 (M = Mo, W; X = S, Se, Te), which are closely related to the indirect-to-direct bandgap transition in monolayers. Here, we report the first direct observation of the transition from indirect to direct bandgap in monolayer samples by using angle-resolved photoemission spectroscopy on high-quality thin films of MoSe2 with variable thickness, grown by molecular beam epitaxy. The band structure measured experimentally indicates a stronger tendency of monolayer MoSe2 towards a direct bandgap, as well as a larger gap size, than theoretically predicted. Moreover, our finding of a significant spin-splitting of ∼180 meV at the valence band maximum of a monolayer MoSe2 film could expand its possible application to spintronic devices.

  View details for DOI 10.1038/nnano.2013.277

  View details for PubMedID 24362235

• Charge-orbital-lattice coupling effects in the dd excitation profile of one-dimensional cuprates PHYSICAL REVIEW B Lee, J. J., Moritz, B., Lee, W. S., Yi, M., Jia, C. J., Sorini, A. P., Kudo, K., Koike, Y., Zhou, K. J., Monney, C., Strocov, V., Patthey, L., Schmitt, T., Devereaux, T. P., Shen, Z. X. 2014; 89 (4)

  View details for DOI 10.1103/PhysRevB.89.041104

  View details for Web of Science ID 000332204000001

• Fast vacancy-mediated oxygen ion incorporation across the ceria-gas electrochemical interface. Nature communications Feng, Z. A., El Gabaly, F., Ye, X., Shen, Z., Chueh, W. C. 2014; 5: 4374-?

  Abstract

  Electrochemical incorporation reactions are ubiquitous in energy storage and conversion devices based on mixed ionic and electronic conductors, such as lithium-ion batteries, solid-oxide fuel cells and water-splitting membranes. The two-way traffic of ions and electrons across the electrochemical interface, coupled with the bulk transport of mass and charge, has been challenging to understand. Here we report an investigation of the oxygen-ion incorporation pathway in CeO2-δ (ceria), one of the most recognized oxygen-deficient compounds, during hydrogen oxidation and water splitting. We probe the response of surface oxygen vacancies, electrons and adsorbates to the electrochemical polarization at the ceria-gas interface. We show that surface oxygen-ion transfer, mediated by oxygen vacancies, is fast. Furthermore, we infer that the electron transfer between cerium cations and hydroxyl ions is the rate-determining step. Our in operando observations reveal the precise roles of surface oxygen vacancy and electron defects in determining the rate of surface incorporation reactions.

  View details for DOI 10.1038/ncomms5374

  View details for PubMedID 25007038

• Orbital character and electron correlation effects on two- and three-dimensional Fermi surfaces in KFe2As2 revealed by angle-resolved photoemission spectroscopy FRONTIERS IN PHYSICS Yoshida, T., Ideta, S., Nishi, I., Fujimori, A., Yi, M., Moore, R. G., Mo, S., Lu, D., Shen, Z., Hussain, Z., Kihou, K., Shirage, P. M., Kito, H., Lee, C., Iyo, A., Eisaki, H., Harima, H. 2014; 2

  View details for DOI 10.3389/fphy.2014.00017

  View details for Web of Science ID 000215935000017

• Examining Electron-Boson Coupling Using Time-Resolved Spectroscopy PHYSICAL REVIEW X Sentef, M., Kemper, A. F., Moritz, B., Freericks, J. K., Shen, Z., Devereaux, T. P. 2013; 3 (4)

  View details for DOI 10.1103/PhysRevX.3.041033

  View details for Web of Science ID 000330128900001

• Discovery of a single topological Dirac fermion in the strong inversion asymmetric compound BiTeCl NATURE PHYSICS Chen, Y. L., Kanou, M., Liu, Z. K., Zhang, H. J., Sobota, J. A., Leuenberger, D., Mo, S. K., Zhou, B., Yang, S., Kirchmann, P. S., Lu, D. H., Moore, R. G., Hussain, Z., Shen, Z. X., Qi, X. L., Sasagawa, T. 2013; 9 (11): 704-708

  View details for DOI 10.1038/NPHYS2768

  View details for Web of Science ID 000326685000010

• Ultrafast charge localization in a stripe-phase nickelate NATURE COMMUNICATIONS Coslovich, G., Huber, B., Lee, W., Chuang, Y., Zhu, Y., Sasagawa, T., Hussain, Z., Bechtel, H. A., Martin, M. C., Shen, Z., Schoenlein, R. W., Kaindl, R. A. 2013; 4

  Abstract

  Self-organized electronically ordered phases are a recurring feature in correlated materials, resulting in, for example, fluctuating charge stripes whose role in high-TC superconductivity is under debate. However, the relevant cause-effect relations between real-space charge correlations and low-energy excitations remain hidden in time-averaged studies. Here we reveal ultrafast charge localization and lattice vibrational coupling as dynamic precursors of stripe formation in the model compound La(1.75)Sr(0.25)NiO4, using ultrafast and equilibrium mid-infrared spectroscopy. The opening of a pseudogap at a crossover temperature T* far above long-range stripe formation establishes the onset of electronic localization, which is accompanied by an enhanced Fano asymmetry of Ni-O stretch vibrations. Ultrafast excitation triggers a sub-picosecond dynamics exposing the synchronous modulation of electron-phonon coupling and charge localization. These results illuminate the role of localization in forming the pseudogap in nickelates, opening a path to understanding this mysterious phase in a broad class of complex oxides.

  View details for DOI 10.1038/ncomms3643

  View details for Web of Science ID 000326472400006

  View details for PubMedCentralID PMC3826635

• Direct Optical Coupling to an Unoccupied Dirac Surface State in the Topological Insulator Bi2Se3 PHYSICAL REVIEW LETTERS Sobota, J. A., Yang, S., Kemper, A. F., Lee, J. J., Schmitt, F. T., Li, W., Moore, R. G., Analytis, J. G., Fisher, I. R., Kirchmann, P. S., Devereaux, T. P., Shen, Z. 2013; 111 (13)

  Abstract

  We characterize the occupied and unoccupied electronic structure of the topological insulator Bi2Se3 by one-photon and two-photon angle-resolved photoemission spectroscopy and slab band structure calculations. We reveal a second, unoccupied Dirac surface state with similar electronic structure and physical origin to the well-known topological surface state. This state is energetically located 1.5 eV above the conduction band, which permits it to be directly excited by the output of a Ti:sapphire laser. This discovery demonstrates the feasibility of direct ultrafast optical coupling to a topologically protected, spin-textured surface state.

  View details for DOI 10.1103/PhysRevLett.111.136802

  View details for PubMedID 24116801

• Electronic structure of the metallic antiferromagnet PdCrO2 measured by angle-resolved photoemission spectroscopy PHYSICAL REVIEW B Sobota, J. A., Kim, K., Takatsu, H., Hashimoto, M., Mo, S., Hussain, Z., Oguchi, T., Shishidou, T., Maeno, Y., Min, B. I., Shen, Z. 2013; 88 (12)

  View details for DOI 10.1103/PhysRevB.88.125109

  View details for Web of Science ID 000324051700006

• Absence of superconductivity in the hole-doped Fe pnictide Ba(Fe1-xMnx)(2)As-2: Photoemission and x-ray absorption spectroscopy studies PHYSICAL REVIEW B Suzuki, H., Yoshida, T., Ideta, S., Shibata, G., Ishigami, K., Kadono, T., Fujimori, A., Hashimoto, M., Lu, D. H., Shen, Z., Ono, K., Sakai, E., Kumigashira, H., Matsuo, M., Sasagawa, T. 2013; 88 (10)

  View details for DOI 10.1103/PhysRevB.88.100501

  View details for Web of Science ID 000323890700002

• Covalent attachment of diamondoid phosphonic Acid dichlorides to tungsten oxide surfaces. Langmuir Li, F. H., Fabbri, J. D., Yurchenko, R. I., Mileshkin, A. N., Hohman, J. N., Yan, H., Yuan, H., Tran, I. C., Willey, T. M., Bagge-Hansen, M., Dahl, J. E., Carlson, R. M., Fokin, A. A., Schreiner, P. R., Shen, Z., Melosh, N. A. 2013; 29 (31): 9790-9797

  Abstract

  Diamondoids (nanometer-sized diamond-like hydrocarbons) are a novel class of carbon nanomaterials that exhibit negative electron affinity (NEA) and strong electron-phonon scattering. Surface-bound diamondoid monolayers exhibit monochromatic photoemission, a unique property that makes them ideal electron sources for electron-beam lithography and high-resolution electron microscopy. However, these applications are limited by the stability of the chemical bonding of diamondoids on surfaces. Here we demonstrate the stable covalent attachment of diamantane phosphonic dichloride on tungsten/tungsten oxide surfaces. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR) spectroscopy revealed that diamondoid-functionalized tungsten oxide films were stable up to 300-350 °C, a substantial improvement over conventional diamondoid thiolate monolayers on gold, which dissociate at 100-200 °C. Extreme ultraviolet (EUV) light stimulated photoemission from these diamondoid phosphonate monolayers exhibited a characteristic monochromatic NEA peak with 0.2 eV full width at half-maximum (fwhm) at room temperature, showing that the unique monochromatization property of diamondoids remained intact after attachment. Our results demonstrate that phosphonic dichloride functionality is a promising approach for forming stable diamondoid monolayers for elevated temperature and high-current applications such as electron emission and coatings in micro/nano electromechanical systems (MEMS/NEMS).

  View details for DOI 10.1021/la401781e

  View details for PubMedID 23855923

• Mapping of unoccupied states and relevant bosonic modes via the time-dependent momentum distribution PHYSICAL REVIEW B Kemper, A. F., Sentef, M., Moritz, B., Kao, C. C., Shen, Z. X., Freericks, J. K., Devereaux, T. P. 2013; 87 (23)

  View details for DOI 10.1103/PhysRevB.87.235139

  View details for Web of Science ID 000321061000001

• Role of Lattice Coupling in Establishing Electronic and Magnetic Properties in Quasi-One-Dimensional Cuprates PHYSICAL REVIEW LETTERS Lee, W. S., Johnston, S., Moritz, B., Lee, J., Yi, M., Zhou, K. J., Schmitt, T., Patthey, L., Strocov, V., Kudo, K., Koike, Y., van den Brink, J., Devereaux, T. P., Shen, Z. X. 2013; 110 (26)

  Abstract

  High resolution resonant inelastic x-ray scattering has been performed to reveal the role of lattice coupling in a family of quasi-1D insulating cuprates, Ca2+5xY2-5xCu5O10. Site-dependent low-energy excitations arising from progressive emissions of a 70 meV lattice vibrational mode are resolved for the first time, providing a direct measurement of electron-lattice coupling strength. We show that such electron-lattice coupling causes doping-dependent distortions of the Cu-O-Cu bond angle, which sets the intrachain spin exchange interactions. Our results indicate that the lattice degrees of freedom are fully integrated into the electronic behavior in low-dimensional systems.

  View details for DOI 10.1103/PhysRevLett.110.265502

  View details for Web of Science ID 000320960300012

  View details for PubMedID 23848894

• Formation of heavy d-electron quasiparticles in Sr3Ru2O7 NEW JOURNAL OF PHYSICS Allan, M. P., Tamai, A., Rozbicki, E., Fischer, M. H., Voss, J., King, P. D., Meevasana, W., Thirupathaiah, S., Rienks, E., Fink, J., Tennant, D. A., Perry, R. S., Mercure, J. F., Wang, M. A., Lee, J., Fennie, C. J., Kim, E., Lawler, M. J., Shen, K. M., Mackenzie, A. P., Shen, Z., Baumberger, F. 2013; 15

  View details for DOI 10.1088/1367-2630/15/6/063029

  View details for Web of Science ID 000320698500003

• High-pressure resistivity technique for quasi-hydrostatic compression experiments REVIEW OF SCIENTIFIC INSTRUMENTS Rotundu, C. R., Cuk, T., Greene, R. L., Shen, Z., Hemley, R. J., Struzhkin, V. V. 2013; 84 (6)

  Abstract

  Diamond anvil cell techniques are now well established and powerful methods for measuring materials properties to very high pressure. However, high pressure resistivity measurements are challenging because the electrical contacts attached to the sample have to survive to extreme stress conditions. Until recently, experiments in a diamond anvil cell were mostly limited to non-hydrostatic or quasi-hydrostatic pressure media other than inert gases. We present here a solution to the problem by using focused ion beam ultrathin lithography for a diamond anvil cell loaded with inert gas (Ne) and show typical resistivity data. These ultrathin leads are deposited on the culet of the diamond and are attaching the sample to the anvil mechanically, therefore allowing for measurements in hydrostatic or nearly hydrostatic conditions of pressure using noble gases like Ne or He as pressure transmitting media.

  View details for DOI 10.1063/1.4809025

  View details for Web of Science ID 000321273500028

  View details for PubMedID 23822353

• Interaction of itinerant electrons and spin fluctuations in electron-doped cuprates PHYSICAL REVIEW B Park, S. R., Morinari, T., Song, D. J., Leem, C. S., Kim, C., Choi, S. K., Choi, K., Kim, J. H., Schmitt, F., Mo, S. K., Lu, D. H., Shen, Z., Eisaki, H., Tohyama, T., Han, J. H., Kim, C. 2013; 87 (17)

  View details for DOI 10.1103/PhysRevB.87.174527

  View details for Web of Science ID 000319801300004

• Real-Time Manifestation of Strongly Coupled Spin and Charge Order Parameters in Stripe-Ordered La1.75Sr0.25NiO4 Nickelate Crystals Using Time-Resolved Resonant X-Ray Diffraction PHYSICAL REVIEW LETTERS Chuang, Y. D., Lee, W. S., Kung, Y. F., Sorini, A. P., Moritz, B., Moore, R. G., Patthey, L., Trigo, M., Lu, D. H., Kirchmann, P. S., Yi, M., Krupin, O., Langner, M., Zhu, Y., Zhou, S. Y., Reis, D. A., Huse, N., ROBINSON, J. S., Kaindl, R. A., Schoenlein, R. W., Johnson, S. L., Foerst, M., Doering, D., Denes, P., Schlotter, W. F., Turner, J. J., Sasagawa, T., Hussain, Z., Shen, Z. X., Devereaux, T. P. 2013; 110 (12)

  Abstract

  We investigate the order parameter dynamics of the stripe-ordered nickelate, La_{1.75}Sr_{0.25}NiO_{4}, using time-resolved resonant x-ray diffraction. In spite of distinct spin and charge energy scales, the two order parameters' amplitude dynamics are found to be linked together due to strong coupling. Additionally, the vector nature of the spin sector introduces a longer reorientation time scale which is absent in the charge sector. These findings demonstrate that the correlation linking the symmetry-broken states does not unbind during the nonequilibrium process, and the time scales are not necessarily associated with the characteristic energy scales of individual degrees of freedom.

  View details for DOI 10.1103/PhysRevLett.110.127404

  View details for Web of Science ID 000316411100019

• Observation of Temperature-Induced Crossover to an Orbital-Selective Mott Phase in A(x)Fe(2-y)Se(2) (A = K, Rb) Superconductors PHYSICAL REVIEW LETTERS Yi, M., Lu, D. H., Yu, R., Riggs, S. C., Chu, J., Lv, B., Liu, Z. K., Lu, M., Cui, Y., Hashimoto, M., Mo, S., Hussain, Z., Chu, C. W., Fisher, I. R., Si, Q., Shen, Z. 2013; 110 (6)

  Abstract

  Using angle-resolved photoemission spectroscopy, we observe the low-temperature state of the A(x)Fe(2-y)Se(2) (A=K, Rb) superconductors to exhibit an orbital-dependent renormalization of the bands near the Fermi level-the d(xy) bands heavily renormalized compared to the d(xz)/d(yz) bands. Upon raising the temperature to above 150 K, the system evolves into a state in which the d(xy) bands have depleted spectral weight while the d(xz)/d(yz) bands remain metallic. Combined with theoretical calculations, our observations can be consistently understood as a temperature-induced crossover from a metallic state at low temperatures to an orbital-selective Mott phase at high temperatures. Moreover, the fact that the superconducting state of A(x)Fe(2-y)Se(2) is near the boundary of such an orbital-selective Mott phase constrains the system to have sufficiently strong on-site Coulomb interactions and Hund's coupling, highlighting the nontrivial role of electron correlation in this family of iron-based superconductors.

  View details for DOI 10.1103/PhysRevLett.110.067003

  View details for PubMedID 23432294

• Unexpected surface implanted layer in static random access memory devices observed by microwave impedance microscope SEMICONDUCTOR SCIENCE AND TECHNOLOGY Kundhikanjana, W., Yang, Y., Tanga, Q., Zhang, K., Lai, K., Ma, Y., Kelly, M. A., Li, X. X., Shen, Z. 2013; 28 (2)

  View details for DOI 10.1088/0268-1242/28/2/025010

  View details for Web of Science ID 000313741500011

• Observing electronic structures on ex-situ grown topological insulator thin films PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS Yao, S. H., Zhou, B., Lu, M. H., Liu, Z. K., Chen, Y. B., Analytis, J. G., Bruene, C., Dang, W. H., Mo, S., Shen, Z., Fisher, I. R., Molenkamp, L. W., Peng, H. L., Hussain, Z., Chen, Y. L. 2013; 7 (1-2): 130-132

  View details for DOI 10.1002/pssr.201206400

  View details for Web of Science ID 000318068800013

• Measurement of Coherent Polarons in the Strongly Coupled Antiferromagnetically Ordered Iron-Chalcogenide Fe1.02Te using Angle-Resolved Photoemission Spectroscopy PHYSICAL REVIEW LETTERS Liu, Z. K., He, R., Lu, D. H., Yi, M., Chen, Y. L., Hashimoto, M., Moore, R. G., Mo, S., Nowadnick, E. A., Hu, J., Liu, T. J., Mao, Z. Q., Devereaux, T. P., Hussain, Z., Shen, Z. 2013; 110 (3)

  Abstract

  The nature of metallicity and the level of electronic correlations in the antiferromagnetically ordered parent compounds are two important open issues for the iron-based superconductivity. We perform a temperature-dependent angle-resolved photoemission spectroscopy study of Fe(1.02)Te, the parent compound for iron chalcogenide superconductors. Deep in the antiferromagnetic state, the spectra exhibit a "peak-dip-hump" line shape associated with two clearly separate branches of dispersion, characteristics of polarons seen in manganites and lightly doped cuprates. As temperature increases towards the Néel temperature (T(N)), we observe a decreasing renormalization of the peak dispersion and a counterintuitive sharpening of the hump linewidth, suggestive of an intimate connection between the weakening electron-phonon (e-ph) coupling and antiferromagnetism. Our finding points to the highly correlated nature of the Fe(1.02)Te ground state featured by strong interactions among the charge, spin, and lattice and a good metallicity plausibly contributed by the coherent polaron motion.

  View details for DOI 10.1103/PhysRevLett.110.037003

  View details for Web of Science ID 000313755000014

  View details for PubMedID 23373946

• PIEZORESISTIVE CANTILEVER PROBES FOR SIMULTANEOUS NANOSCALE TOPOGRAPHY AND CONDUCTIVITY IMAGING 26th IEEE International Conference on Micro Electro Mechanical Systems (MEMS) Yang, Y., Ma, Y., Haemmerli, A., Lai, K., Kundhikanjana, W., Harjee, N., Pruitt, B., Li, X., Kelly, M., Shen, Z. IEEE. 2013: 323–326

  View details for Web of Science ID 000320549200083

• Tracking Charge Localization via Transient Electron-Phonon Coupling in a Stripe-ordered Nickelate Coslovich, G., Huber, B., Lee, W., Chuang, Y., Zhu, Y., Sasagawa, T., Hussain, Z., Bechtel, H. A., Martin, M. C., Shen, Z., Schoenlein, R. W., Kaindl, R. A., IEEE IEEE. 2013

  View details for Web of Science ID 000355262505316

• 26aEC-13 Superconducting gap in isovalent-substituted Ba(Fe_<0.65>Ru_<0.35>)_2As_2 observed by angle-resolved photoemission spectroscopy The Physical Society of Japan Liu, L., Suzuki, H., Horio, M., II Ambolode, L., Xu, J., Ideta, S., Okazaki, K., Fujimori, A., Yoshida, T., Hashimoto, M., Lu, D., Shen, Z., Nakajima, M., Kihou, K., Lee, L., Iyo, A., Eisaki, H., Uchida, S. 2013: 496
• Time-resolved Fermi surface mapping of the charge density wave material DyTe3 18th International Conference on Ultrafast Phenomena Rettig, L., Cortes, R., Chu, J., Fisher, I. R., Schmitt, F., Kirchmann, P. S., Moore, R. G., Shen, Z., Wolf, M., Bovensiepen, U. E D P SCIENCES. 2013

  View details for DOI 10.1051/epjconf/20134103025

  View details for Web of Science ID 000320558600082

• Excitation of Electromagnetic Waves in a Thin Water Layer Using a Coaxial Probe 3rd Asia-Pacific Microwave Conference Proceedings (APMC) Hu, Z., Shen, Z., Wu, W. IEEE. 2013: 128–130

  View details for Web of Science ID 000330851900042

• Ultrafast Mid-infrared Spectroscopy of the Charge- and Spin-ordered Nickelates Conference on Ultrafast Phenomena and Nanophotonics XVII Coslovich, G., Huber, B., Lee, W., Chuang, Y., Zhu, Y., Sasagawa, T., Hussain, Z., Bechtel, H. A., Martin, M. C., Schoenlein, R. W., Shen, Z., Kaindl, R. A. SPIE-INT SOC OPTICAL ENGINEERING. 2013

  View details for DOI 10.1117/12.2005366

  View details for Web of Science ID 000322829300006

• Ultrast Mid-infrared Spectroscopy of the Charge- and Spin-Ordered Nickelate La1.75Sr0.25NiO4 18th International Conference on Ultrafast Phenomena Coslovich, G., Huber, B., Lee, W., Chuang, Y., Zhu, Y., Sasagawa, T., Hussain, Z., Bechtel, H. A., Martin, M. C., Schoenlein, R. W., Shen, Z., Kaindl, R. A. E D P SCIENCES. 2013

  View details for DOI 10.1051/epjconf/20134103016

  View details for Web of Science ID 000320558600073

• Photon-enhanced thermionic emission from heterostructures with low interface recombination. Nature communications Schwede, J. W., Sarmiento, T., NARASIMHAN, V. K., Rosenthal, S. J., Riley, D. C., Schmitt, F., Bargatin, I., Sahasrabuddhe, K., Howe, R. T., Harris, J. S., Melosh, N. A., Shen, Z. 2013; 4: 1576-?

  Abstract

  Photon-enhanced thermionic emission is a method of solar-energy conversion that promises to combine photon and thermal processes into a single mechanism, overcoming fundamental limits on the efficiency of photovoltaic cells. Photon-enhanced thermionic emission relies on vacuum emission of photoexcited electrons that are in thermal equilibrium with a semiconductor lattice, avoiding challenging non-equilibrium requirements and exotic material properties. However, although previous work demonstrated the photon-enhanced thermionic emission effect, efficiency has until now remained very low. Here we describe electron-emission measurements on a GaAs/AlGaAs heterostructure that introduces an internal interface, decoupling the basic physics of photon-enhanced thermionic emission from the vacuum emission process. Quantum efficiencies are dramatically higher than in previous experiments because of low interface recombination and are projected to increase another order of magnitude with more stable, low work-function coatings. The results highlight the effectiveness of the photon-enhanced thermionic emission process and demonstrate that efficient photon-enhanced thermionic emission is achievable, a key step towards realistic photon-enhanced thermionic emission based energy conversion.

  View details for DOI 10.1038/ncomms2577

  View details for PubMedID 23481384

• Microbead-separated thermionic energy converter with enhanced emission current PHYSICAL CHEMISTRY CHEMICAL PHYSICS Littau, K. A., Sahasrabuddhe, K., Barfield, D., Yuan, H., Shen, Z., Howe, R. T., Melosh, N. A. 2013; 15 (34): 14442-14446

  Abstract

  The efficiency of thermionic energy converters is a strong function of the inter-electrode separation due to space-charge limitations. Here we demonstrate vacuum thermionic energy converters constructed using barium dispenser cathodes and thin film tungsten anodes, separated by size specific alumina microbeads for simple device fabrication and inter-electrode gap control. The current and device efficiency at the maximum power point are strongly dependent on the inter-electrode gap, with a maximum device efficiency of 0.61% observed for a gap on the order of 5 μm. Paths to further reductions in space charge and improved anode work function are outlined with potential for over an order of magnitude improvement in output power and efficiency.

  View details for DOI 10.1039/c3cp52895b

  View details for Web of Science ID 000322725000036

  View details for PubMedID 23881241

• Photocathode device using diamondoid and cesium bromide films APPLIED PHYSICS LETTERS Clay, W. A., Maldonado, J. R., Pianetta, P., Dahl, J. E., Carlson, R. M., Schreiner, P. R., Fokin, A. A., Tkachenko, B. A., Melosh, N. A., Shen, Z. 2012; 101 (24)

  View details for DOI 10.1063/1.4769043

  View details for Web of Science ID 000312490000024

• Controlling the carriers of topological insulators by bulk and surface doping SEMICONDUCTOR SCIENCE AND TECHNOLOGY Zhou, B., Liu, Z. K., Analytis, J. G., Igarashi, K., Mo, S. K., Lu, D. H., Moore, R. G., Fisher, I. R., Sasagawa, T., Shen, Z. X., Hussain, Z., Chen, Y. L. 2012; 27 (12)

  View details for DOI 10.1088/0268-1242/27/12/124002

  View details for Web of Science ID 000311844400004

• Phase competition in trisected superconducting dome PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Vishik, I. M., Hashimoto, M., He, R., LeeB, W., Schmitt, F., Lu, D., Moore, R. G., Zhang, C., Meevasana, W., Sasagawa, T., Uchida, S., Fujita, K., Ishida, S., Ishikado, M., Yoshida, Y., Eisaki, H., Hussain, Z., Devereaux, T. P., Shen, Z. 2012; 109 (45): 18332-18337

  Abstract

  A detailed phenomenology of low energy excitations is a crucial starting point for microscopic understanding of complex materials, such as the cuprate high-temperature superconductors. Because of its unique momentum-space discrimination, angle-resolved photoemission spectroscopy (ARPES) is ideally suited for this task in the cuprates, where emergent phases, particularly superconductivity and the pseudogap, have anisotropic gap structure in momentum space. We present a comprehensive doping- and temperature-dependence ARPES study of spectral gaps in Bi(2)Sr(2)CaCu(2)O(8+δ), covering much of the superconducting portion of the phase diagram. In the ground state, abrupt changes in near-nodal gap phenomenology give spectroscopic evidence for two potential quantum critical points, p = 0.19 for the pseudogap phase and p = 0.076 for another competing phase. Temperature dependence reveals that the pseudogap is not static below T(c) and exists p > 0.19 at higher temperatures. Our data imply a revised phase diagram that reconciles conflicting reports about the endpoint of the pseudogap in the literature, incorporates phase competition between the superconducting gap and pseudogap, and highlights distinct physics at the edge of the superconducting dome.

  View details for DOI 10.1073/pnas.1209471109

  View details for Web of Science ID 000311156700031

  View details for PubMedID 23093670

  View details for PubMedCentralID PMC3494935

• A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission JOURNAL OF APPLIED PHYSICS Sahasrabuddhe, K., Schwede, J. W., Bargatin, I., Jean, J., Howe, R. T., Shen, Z., Melosh, N. A. 2012; 112 (9)

  View details for DOI 10.1063/1.4764106

  View details for Web of Science ID 000311968400139

• Batch-fabricated cantilever probes with electrical shielding for nanoscale dielectric and conductivity imaging JOURNAL OF MICROMECHANICS AND MICROENGINEERING Yang, Y., Lai, K., Tang, Q., Kundhikanjana, W., Kelly, M. A., Zhang, K., Shen, Z., Li, X. 2012; 22 (11)

  View details for DOI 10.1088/0960-1317/22/11/115040

  View details for Web of Science ID 000310534400041

• Oxygen-content-dependent electronic structures of electron-doped cuprates PHYSICAL REVIEW B Song, D., Park, S. R., Kim, C., Kim, Y., Leem, C., Choi, S., Jung, W., Koh, Y., Han, G., Yoshida, Y., Eisaki, H., Lu, D. H., Shen, Z., Kim, C. 2012; 86 (14)

  View details for DOI 10.1103/PhysRevB.86.144520

  View details for Web of Science ID 000309903100004

• Diamondoid coating enables disruptive approach for chemical and magnetic imaging with 10 nm spatial resolution APPLIED PHYSICS LETTERS Ishiwata, H., Acremann, Y., Scholl, A., Rotenberg, E., Hellwig, O., Dobisz, E., Doran, A., Tkachenko, B. A., Fokin, A. A., Schreiner, P. R., Dahl, J. E., Carlson, R. M., Melosh, N., Shen, Z., Ohldag, H. 2012; 101 (16)

  View details for DOI 10.1063/1.4756893

  View details for Web of Science ID 000310669300052

• Superconductivity distorted by the coexisting pseudogap in the antinodal region of Bi1.5Pb0.55Sr1.6La0.4CuO6+delta: A photon-energy-dependent angle-resolved photoemission study PHYSICAL REVIEW B Hashimoto, M., He, R., Vishik, I. M., Schmitt, F., Moore, R. G., Lu, D. H., Yoshida, Y., Eisaki, H., Hussain, Z., Devereaux, T. P., Shen, Z. 2012; 86 (9)

  View details for DOI 10.1103/PhysRevB.86.094504

  View details for Web of Science ID 000308287300015

• Electronic reconstruction through the structural and magnetic transitions in detwinned NaFeAs NEW JOURNAL OF PHYSICS Yi, M., Lu, D. H., Moore, R. G., Kihou, K., Lee, C., Iyo, A., Eisaki, H., Yoshida, T., Fujimori, A., Shen, Z. 2012; 14

  View details for DOI 10.1088/1367-2630/14/7/073019

  View details for Web of Science ID 000307070700003

• Intrinsic ultrathin topological insulators grown via molecular beam epitaxy characterized by in-situ angle resolved photoemission spectroscopy APPLIED PHYSICS LETTERS Lee, J. J., Schmitt, F. T., Moore, R. G., Vishik, I. M., Ma, Y., Shen, Z. X. 2012; 101 (1)

  View details for DOI 10.1063/1.4733317

  View details for Web of Science ID 000306144800073

• Emerging coherence with unified energy, temperature, and lifetime scale in heavy fermion YbRh2Si2 PHYSICAL REVIEW B Mo, S., Lee, W. S., Schmitt, F., Chen, Y. L., Lu, D. H., Capan, C., Kim, D. J., Fisk, Z., Zhang, C., Hussain, Z., Shen, Z. 2012; 85 (24)

  View details for DOI 10.1103/PhysRevB.85.241103

  View details for Web of Science ID 000305558500001

• Phase fluctuations and the absence of topological defects in a photo-excited charge-ordered nickelate NATURE COMMUNICATIONS Lee, W. S., Chuang, Y. D., Moore, R. G., Zhu, Y., Patthey, L., Trigo, M., Lu, D. H., Kirchmann, P. S., Krupin, O., Yi, M., Langner, M., Huse, N., ROBINSON, J. S., Chen, Y., Zhou, S. Y., Coslovich, G., Huber, B., Reis, D. A., Kaindl, R. A., Schoenlein, R. W., Doering, D., Denes, P., Schlotter, W. F., Turner, J. J., Johnson, S. L., Foerst, M., Sasagawa, T., Kung, Y. F., Sorini, A. P., Kemper, A. F., Moritz, B., Devereaux, T. P., Lee, D., Shen, Z. X., Hussain, Z. 2012; 3

  Abstract

  The dynamics of an order parameter's amplitude and phase determines the collective behaviour of novel states emerging in complex materials. Time- and momentum-resolved pump-probe spectroscopy, by virtue of measuring material properties at atomic and electronic time scales out of equilibrium, can decouple entangled degrees of freedom by visualizing their corresponding dynamics in the time domain. Here we combine time-resolved femotosecond optical and resonant X-ray diffraction measurements on charge ordered La(1.75)Sr(0.25)NiO(4) to reveal unforeseen photoinduced phase fluctuations of the charge order parameter. Such fluctuations preserve long-range order without creating topological defects, distinct from thermal phase fluctuations near the critical temperature in equilibrium. Importantly, relaxation of the phase fluctuations is found to be an order of magnitude slower than that of the order parameter's amplitude fluctuations, and thus limits charge order recovery. This new aspect of phase fluctuations provides a more holistic view of the phase's importance in ordering phenomena of quantum matter.

  View details for DOI 10.1038/ncomms1837

  View details for Web of Science ID 000304611400033

  View details for PubMedID 22588300

• Resonant enhancement of charge density wave diffraction in the rare-earth tritellurides PHYSICAL REVIEW B Lee, W. S., Sorini, A. P., Yi, M., Chuang, Y. D., Moritz, B., Yang, W. L., Chu, J., Kuo, H. H., Gonzalez, A. G., Fisher, I. R., Hussain, Z., Devereaux, T. P., Shen, Z. X. 2012; 85 (15)

  View details for DOI 10.1103/PhysRevB.85.155142

  View details for Web of Science ID 000303309600003

• Evidence for the Importance of Extended Coulomb Interactions and Forward Scattering in Cuprate Superconductors PHYSICAL REVIEW LETTERS Johnston, S., Vishik, I. M., Lee, W. S., Schmitt, F., Uchida, S., Fujita, K., Ishida, S., Nagaosa, N., Shen, Z. X., Devereaux, T. P. 2012; 108 (16)

  Abstract

  The prevalent view of the high-temperature superconducting cuprates is that their essential low-energy physics is captured by local Coulomb interactions. However, this view been challenged recently by studies indicating the importance of longer-range components. Motivated by this, we demonstrate the importance of these components by examining the electron-phonon (e-ph) interaction with acoustic phonons in connection with the recently discovered renormalization in the near-nodal low-energy (~8-15 meV) dispersion of Bi(2)Sr(2)CaCu(2)O(8+δ). By studying its nontrivial momentum and doping dependence we conclude a predominance of forward scattering arising from the direct interplay between the e-ph and extended Coulomb interactions. Our results thus demonstrate how the low-energy renormalization can provide a pathway to new insights into how these interactions interplay with one another and influence pairing and dynamics in the cuprates.

  View details for DOI 10.1103/PhysRevLett.108.166404

  View details for Web of Science ID 000303070600015

  View details for PubMedID 22680740

• Topological insulator nanostructures for near-infrared transparent flexible electrodes NATURE CHEMISTRY Peng, H., Dang, W., Cao, J., Chen, Y., Wu, D., Zheng, W., Li, H., Shen, Z., Liu, Z. 2012; 4 (4): 281-286

  Abstract

  Topological insulators are an intriguing class of materials with an insulating bulk state and gapless Dirac-type edge/surface states. Recent theoretical work predicts that few-layer topological insulators are promising candidates for broadband and high-performance optoelectronic devices due to their spin-momentum-locked massless Dirac edge/surface states, which are topologically protected against all time-reversal-invariant perturbations. Here, we present the first experimental demonstration of near-infrared transparent flexible electrodes based on few-layer topological-insulator Bi(2)Se(3) nanostructures epitaxially grown on mica substrates by means of van der Waals epitaxy. The large, continuous, Bi(2)Se(3)-nanosheet transparent electrodes have single Dirac cone surface states, and exhibit sheet resistances as low as ~330 Ω per square, with a transparency of more than 70% over a wide range of wavelengths. Furthermore, Bi(2)Se(3)-nanosheet transparent electrodes show high chemical and thermal stabilities as well as excellent mechanical durability, which may lead to novel optoelectronic devices with unique properties.

  View details for DOI 10.1038/nchem.1277

  View details for Web of Science ID 000301983400013

  View details for PubMedID 22437712

• Low-impedance shielded tip piezoresistive probe enables portable microwave impedance microscopy MICRO & NANO LETTERS Haemmerli, A. J., Nielsen, R. T., Kundhikanjana, W., HARJEE, N., Goldhaber-Gordon, D., Shen, Z. X., Pruitt, B. L. 2012; 7 (4): 321-324

  View details for DOI 10.1049/mnl.2011.0679

  View details for Web of Science ID 000303341600008

• Energy scale directly related to superconductivity in high-T-c cuprates: Universality from the temperature-dependent angle-resolved photoemission of Bi2Sr2Ca2Cu3O10+delta PHYSICAL REVIEW B Ideta, S., Yoshida, T., Fujimori, A., Anzai, H., Fujita, T., Ino, A., Arita, M., Namatame, H., Taniguchi, M., Shen, Z., Takashima, K., Kojima, K., Uchida, S. 2012; 85 (10)

  View details for DOI 10.1103/PhysRevB.85.104515

  View details for Web of Science ID 000301705500004

• Ultrafast Optical Excitation of a Persistent Surface-State Population in the Topological Insulator Bi2Se3 PHYSICAL REVIEW LETTERS Sobota, J. A., Yang, S., Analytis, J. G., Chen, Y. L., Fisher, I. R., Kirchmann, P. S., Shen, Z. 2012; 108 (11)

  Abstract

  Using femtosecond time- and angle-resolved photoemission spectroscopy, we investigated the nonequilibrium dynamics of the topological insulator Bi2Se3. We studied p-type Bi2Se3, in which the metallic Dirac surface state and bulk conduction bands are unoccupied. Optical excitation leads to a metastable population at the bulk conduction band edge, which feeds a nonequilibrium population of the surface state persisting for >10 ps. This unusually long-lived population of a metallic Dirac surface state with spin texture may present a channel in which to drive transient spin-polarized currents.

  View details for DOI 10.1103/PhysRevLett.108.117403

  View details for Web of Science ID 000301478400014

  View details for PubMedID 22540508

• Subband Structure of a Two-Dimensional Electron Gas Formed at the Polar Surface of the Strong Spin-Orbit Perovskite KTaO3 PHYSICAL REVIEW LETTERS King, P. D., He, R. H., Eknapakul, T., Buaphet, P., Mo, S., Kaneko, Y., Harashima, S., Hikita, Y., Bahramy, M. S., Bell, C., Hussain, Z., Tokura, Y., Shen, Z., Hwang, H. Y., Baumberger, F., Meevasana, W. 2012; 108 (11)

  Abstract

  We demonstrate the formation of a two-dimensional electron gas (2DEG) at the (100) surface of the 5d transition-metal oxide KTaO3. From angle-resolved photoemission, we find that quantum confinement lifts the orbital degeneracy of the bulk band structure and leads to a 2DEG composed of ladders of subband states of both light and heavy carriers. Despite the strong spin-orbit coupling, our measurements provide a direct upper bound for the potential Rashba spin splitting of only Δk(parallel)}~0.02 Å(-1) at the Fermi level. The polar nature of the KTaO3(100) surface appears to help mediate the formation of the 2DEG as compared to nonpolar SrTiO3(100).

  View details for DOI 10.1103/PhysRevLett.108.117602

  View details for Web of Science ID 000301478400015

  View details for PubMedID 22540511

• Robust topological surface state against direct surface contamination PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES Liu, Z. K., Chen, Y. L., Analytis, J. G., Mo, S. K., Lu, D. H., Moore, R. G., Fisher, I. R., Hussain, Z., Shen, Z. X. 2012; 44 (5): 891-894

  View details for DOI 10.1016/j.physe.2011.10.023

  View details for Web of Science ID 000303276200005

• Femtosecond Dynamics of the Collinear-to-Spiral Antiferromagnetic Phase Transition in CuO PHYSICAL REVIEW LETTERS Johnson, S. L., de Souza, R. A., Staub, U., Beaud, P., Moehr-Vorobeva, E., Ingold, G., Caviezel, A., Scagnoli, V., Schlotter, W. F., Turner, J. J., Krupin, O., Lee, W., Chuang, Y., Patthey, L., Moore, R. G., Lu, D., Yi, M., Kirchmann, P. S., Trigo, M., Denes, P., Doering, D., Hussain, Z., Shen, Z., Prabhakaran, D., Boothroyd, A. T. 2012; 108 (3)

  Abstract

  We report on the ultrafast dynamics of magnetic order in a single crystal of CuO at a temperature of 207 K in response to strong optical excitation using femtosecond resonant x-ray diffraction. In the experiment, a femtosecond laser pulse induces a sudden, nonequilibrium increase in magnetic disorder. After a short delay ranging from 400 fs to 2 ps, we observe changes in the relative intensity of the magnetic ordering diffraction peaks that indicate a shift from a collinear commensurate phase to a spiral incommensurate phase. These results indicate that the ultimate speed for this antiferromagnetic reorientation transition in CuO is limited by the long-wavelength magnetic excitation connecting the two phases.

  View details for DOI 10.1103/PhysRevLett.108.037203

  View details for Web of Science ID 000299329100026

  View details for PubMedID 22400779

• Angle-Resolved Photoemission Studies of Quantum Materials ANNUAL REVIEW OF CONDENSED MATTER PHYSICS, VOL 3 Lu, D., Vishik, I. M., Yi, M., Chen, Y., Moore, R. G., Shen, Z. 2012; 3: 129-167

  View details for DOI 10.1146/annurev-conmatphys-020911-125027

  View details for Web of Science ID 000301793100008

• Encapsulated thermionic energy converter with stiffened suspension Lee, J., Bargatin, I., Iwami, K., Littau, K. A., Vincent, M., Maboudian, R., Shen, Z., Melosh, N. A., Howe, R. T. 2012: 493–96
• MICROFABRICATED SILICON CARBIDE THERMIONIC ENERGY CONVERTER FOR SOLAR ELECTRICITY GENERATION 25th IEEE International Conference on Micro Electro Mechanical Systems (MEMS) Lee, J. H., Bargatin, I., Gwinn, T. O., Vincent, M., Littau, K. A., Maboudian, R., Shen, Z., Melosh, N. A., Howe, R. T. IEEE. 2012

  View details for Web of Science ID 000312912800317

• LOW-IMPEDANCE SHIELDED TIP PIEZORESISTIVE PROBE ENABLES PORTABLE MICROWAVE IMPEDANCE MICROSCOPY 25th IEEE International Conference on Micro Electro Mechanical Systems (MEMS) Haemmerli, A. J., Nielsen, R. T., Kundhikanjana, W., HARJEE, N., Lai, K., Yang, Y. L., Goldhaber-Gordon, D., Shen, Z. X., Pruitt, B. L. IEEE. 2012

  View details for Web of Science ID 000312912800070

• Pseudogap, Superconducting Gap, and Fermi Arc in High-T-c Cuprates Revealed by Angle-Resolved Photoemission Spectroscopy JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Yoshida, T., Hashimoto, M., Vishik, I. M., Shen, Z., Fujimori, A. 2012; 81 (1)

  View details for DOI 10.1143/JPSJ.81.011006

  View details for Web of Science ID 000298553000006

• In-plane electronic anisotropy of underdoped '122' Fe-arsenide superconductors revealed by measurements of detwinned single crystals REPORTS ON PROGRESS IN PHYSICS Fisher, I. R., Degiorgi, L., Shen, Z. X. 2011; 74 (12)

  View details for DOI 10.1088/0034-4885/74/12/124506

  View details for Web of Science ID 000298079500007

• Photoluminescence of diamondoid crystals JOURNAL OF APPLIED PHYSICS Clay, W. A., Sasagawa, T., Iwasa, A., Liu, Z., Dahl, J. E., Carlson, R. M., Kelly, M., Melosh, N., Shen, Z. 2011; 110 (9)

  View details for DOI 10.1063/1.3657522

  View details for Web of Science ID 000297062100028

• Ambipolar field effect in the ternary topological insulator (BixSb1-x)(2)Te-3 by composition tuning NATURE NANOTECHNOLOGY Kong, D., Chen, Y., Cha, J. J., Zhang, Q., Analytis, J. G., Lai, K., Liu, Z., Hong, S. S., Koski, K. J., Mo, S., Hussain, Z., Fisher, I. R., Shen, Z., Cui, Y. 2011; 6 (11): 705-709

  Abstract

  Topological insulators exhibit a bulk energy gap and spin-polarized surface states that lead to unique electronic properties, with potential applications in spintronics and quantum information processing. However, transport measurements have typically been dominated by residual bulk charge carriers originating from crystal defects or environmental doping, and these mask the contribution of surface carriers to charge transport in these materials. Controlling bulk carriers in current topological insulator materials, such as the binary sesquichalcogenides Bi2Te3, Sb2Te3 and Bi2Se3, has been explored extensively by means of material doping and electrical gating, but limited progress has been made to achieve nanostructures with low bulk conductivity for electronic device applications. Here we demonstrate that the ternary sesquichalcogenide (Bi(x)Sb(1-x))2Te3 is a tunable topological insulator system. By tuning the ratio of bismuth to antimony, we are able to reduce the bulk carrier density by over two orders of magnitude, while maintaining the topological insulator properties. As a result, we observe a clear ambipolar gating effect in (Bi(x)Sb(1-x))2Te3 nanoplate field-effect transistor devices, similar to that observed in graphene field-effect transistor devices. The manipulation of carrier type and density in topological insulator nanostructures demonstrated here paves the way for the implementation of topological insulators in nanoelectronics and spintronics.

  View details for DOI 10.1038/NNANO.2011.172

  View details for Web of Science ID 000296737300007

  View details for PubMedID 21963714

• Imaging of Coulomb-Driven Quantum Hall Edge States PHYSICAL REVIEW LETTERS Lai, K., Kundhikanjana, W., Kelly, M. A., Shen, Z., Shabani, J., Shayegan, M. 2011; 107 (17)

  Abstract

  The edges of a two-dimensional electron gas (2DEG) in the quantum Hall effect (QHE) regime are divided into alternating metallic and insulating strips, with their widths determined by the energy gaps of the QHE states and the electrostatic Coulomb interaction. Local probing of these submicrometer features, however, is challenging due to the buried 2DEG structures. Using a newly developed microwave impedance microscope, we demonstrate the real-space conductivity mapping of the edge and bulk states. The sizes, positions, and field dependence of the edge strips around the sample perimeter agree quantitatively with the self-consistent electrostatic picture. The evolution of microwave images as a function of magnetic fields provides rich microscopic information around the ν=2 QHE state.

  View details for DOI 10.1103/PhysRevLett.107.176809

  View details for Web of Science ID 000296984100011

  View details for PubMedID 22107561

• Widespread spin polarization effects in photoemission from topological insulators PHYSICAL REVIEW B Jozwiak, C., Chen, Y. L., Fedorov, A. V., Analytis, J. G., Rotundu, C. R., Schmid, A. K., Denlinger, J. D., Chuang, Y., Lee, D., Fisher, I. R., Birgeneau, R. J., Shen, Z., Hussain, Z., Lanzara, A. 2011; 84 (16)

  View details for DOI 10.1103/PhysRevB.84.165113

  View details for Web of Science ID 000299004900003

• Hidden Itinerant-Spin Phase in Heavily Overdoped La2-xSrxCuO4 Superconductors Revealed by Dilute Fe Doping: A Combined Neutron Scattering and Angle-Resolved Photoemission Study PHYSICAL REVIEW LETTERS He, R., Fujita, M., Enoki, M., Hashimoto, M., Iikubo, S., Mo, S., Yao, H., Adachi, T., Koike, Y., Hussain, Z., Shen, Z., Yamada, K. 2011; 107 (12)

  Abstract

  We demonstrated experimentally a direct way to probe a hidden propensity to the formation of a spin-density wave in a nonmagnetic metal with strong Fermi surface nesting. Substituting Fe for a tiny amount of Cu (1%) induced an incommensurate magnetic order below 20 K in heavily overdoped La(2-x)Sr(x)CuO(4). Elastic neutron scattering suggested that this order cannot be ascribed to the localized spins on Cu or doped Fe. Angle-resolved photoemission revealed a strong Fermi surface nesting inherent in the pristine La(2-x)Sr(x)CuO(4) that likely drives this order. Our finding presents the first example of the long-sought "itinerant-spin extreme" of cuprates, where the spins of itinerant doped holes define the magnetic ordering ground state; it complements the current picture of cuprate spin physics that highlights the predominant role of localized spins at lower dopings.

  View details for DOI 10.1103/PhysRevLett.107.127002

  View details for Web of Science ID 000294929400010

  View details for PubMedID 22026791

• Polaronic metal in lightly doped high-T-c cuprates EPL Mishchenko, A. S., Nagaosa, N., Shen, K. M., Shen, Z., Zhou, X. J., Devereaux, T. P. 2011; 95 (5)

  View details for DOI 10.1209/0295-5075/95/57007

  View details for Web of Science ID 000294325500031

• Angle-resolved photoemission spectroscopy study of PrFeAsO0.7: Comparison with LaFePO PHYSICAL REVIEW B Nishi, I., Ishikado, M., Ideta, S., Malaeb, W., Yoshida, T., Fujimori, A., Kotani, Y., Kubota, M., Ono, K., Yi, M., Lu, D. H., Moore, R., Shen, Z., Iyo, A., Kihou, K., Kito, H., Eisaki, H., Shamoto, S., Arita, R. 2011; 84 (1)

  View details for DOI 10.1103/PhysRevB.84.014504

  View details for Web of Science ID 000292823600003

• Ultrafast electron dynamics in the charge density wave material TbTe3 NEW JOURNAL OF PHYSICS Schmitt, F., Kirchmann, P. S., Bovensiepen, U., Moore, R. G., Chu, J., Lu, D. H., Rettig, L., Wolf, M., Fisher, I. R., Shen, Z. 2011; 13

  View details for DOI 10.1088/1367-2630/13/6/063022

  View details for Web of Science ID 000292139400004

• Rapid Surface Oxidation as a Source of Surface Degradation Factor for Bi2Se3 ACS NANO Kong, D., Cha, J. J., Lai, K., Peng, H., Analytis, J. G., Meister, S., Chen, Y., Zhang, H., Fisher, I. R., Shen, Z., Cui, Y. 2011; 5 (6): 4698-4703

  Abstract

  Bismuth selenide (Bi(2)Se(3)) is a topological insulator with metallic surface states (SS) residing in a large bulk bandgap. In experiments, synthesized Bi(2)Se(3) is often heavily n-type doped due to selenium vacancies. Furthermore, it is discovered from experiments on bulk single crystals that Bi(2)Se(3) gets additional n-type doping after exposure to the atmosphere, thereby reducing the relative contribution of SS in total conductivity. In this article, transport measurements on Bi(2)Se(3) nanoribbons provide additional evidence of such environmental doping process. Systematic surface composition analyses by X-ray photoelectron spectroscopy reveal fast formation and continuous growth of native oxide on Bi(2)Se(3) under ambient conditions. In addition to n-type doping at the surface, such surface oxidation is likely the material origin of the degradation of topological SS. Appropriate surface passivation or encapsulation may be required to probe topological SS of Bi(2)Se(3) by transport measurements.

  View details for DOI 10.1021/nn200556h

  View details for Web of Science ID 000292055200052

  View details for PubMedID 21568290

• High-energy anomaly in Nd2-xCexCuO4 investigated by angle-resolved photoemission spectroscopy and quantum Monte Carlo simulations PHYSICAL REVIEW B Schmitt, F., Moritz, B., Johnston, S., Mo, S., Hashimoto, M., Moore, R. G., Lu, D., Motoyama, E., Greven, M., Devereaux, T. P., Shen, Z. 2011; 83 (19)

  View details for DOI 10.1103/PhysRevB.83.195123

  View details for Web of Science ID 000290711300003

• Photoemission studies on electron doped cuprate Pr0.85LaCe0.15CuO4: Revisiting the chemical pressure effect International Conference on Spectroscopies in Novel Superconductors (SNS2010) Song, D. J., Kyung, W. S., Park, S. R., Leem, C. S., Kim, C., Kim, Y. K., Choi, S. K., Jung, W. S., Koh, Y. Y., Choi, H. Y., Han, G., Yoshida, Y., Eisaki, H., Lu, D. H., Shen, Z., Kim, C. PERGAMON-ELSEVIER SCIENCE LTD. 2011: 533–35

  View details for DOI 10.1016/j.jpcs.2010.10.069

  View details for Web of Science ID 000291518100057

• Nanoscale microwave microscopy using shielded cantilever probes APPLIED NANOSCIENCE Lai, K., Kundhikanjana, W., Kelly, M. A., Shen, Z. 2011; 1 (1): 13–18

  View details for DOI 10.1007/s13204-011-0002-7

  View details for Web of Science ID 000497849300003

• Self-energy analysis of multiple-bosonic mode coupling in Sr2RuO4 International Conference on Spectroscopies in Novel Superconductors (SNS2010) Kim, C., Kyung, W. S., Park, S. R., Leem, C. S., Song, D. J., Kim, Y. K., Choi, S. K., Jung, W. S., Koh, Y. Y., Choi, H. Y., Yoshida, Y., Moore, R. G., Shen, Z., Kim, C. PERGAMON-ELSEVIER SCIENCE LTD. 2011: 556–58

  View details for DOI 10.1016/j.jpcs.2010.10.068

  View details for Web of Science ID 000291518100063

• Fermi surfaces and quasi-particle band dispersions of the iron pnictides superconductor KFe2As2 observed by angle-resolved photoemission spectroscopy International Conference on Spectroscopies in Novel Superconductors (SNS2010) Yoshida, T., Nishi, I., Fujimori, A., Yi, M., Moore, R. G., Luc, D., Shen, Z., Kihou, K., Shirage, P. M., Kito, H., Lee, C. H., Iyo, A., Eisaki, H., Harima, H. PERGAMON-ELSEVIER SCIENCE LTD. 2011: 465–68

  View details for DOI 10.1016/j.jpcs.2010.10.064

  View details for Web of Science ID 000291518100041

• Symmetry-breaking orbital anisotropy observed for detwinned Ba(Fe1-xCox)(2)As-2 above the spin density wave transition PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Yi, M., Lu, D., Chu, J., Analytis, J. G., Sorini, A. P., Kemper, A. F., Moritz, B., Mo, S., Moore, R. G., Hashimoto, M., Lee, W., Hussain, Z., Devereaux, T. P., Fisher, I. R., Shen, Z. 2011; 108 (17): 6878-6883

  View details for DOI 10.1073/pnas.1015572108

  View details for Web of Science ID 000289888500040

• Reaffirming the d(x2-y2) Superconducting Gap Using the Autocorrelation Angle-Resolved Photoemission Spectroscopy of Bi1.5Pb0.55Sr1.6La0.4CuO6+delta PHYSICAL REVIEW LETTERS Hashimoto, M., He, R., Testaud, J. P., Meevasana, W., Moore, R. G., Lu, D. H., Yoshida, Y., Eisaki, H., Devereaux, T. P., Hussain, Z., Shen, Z. 2011; 106 (16)

  Abstract

  Knowledge of the gap function is important to understand the pairing mechanism for high-temperature (T(c)) superconductivity. However, Fourier transform scanning tunneling spectroscopy (FT STS) and angle-resolved photoemission spectroscopy (ARPES) in the cuprates have reported contradictory gap functions, with FT-STS results deviating strongly from a canonical d(x2-y2) form. By applying an "octet model" analysis to autocorrelation ARPES, we reveal that a contradiction occurs because the octet model does not consider the effects of matrix elements and the pseudogap. This reaffirms the canonical d(x2-y2) superconducting gap around the node, which can be directly determined from ARPES. Further, our study suggests that the FT-STS reported fluctuating superconductivity around the node at far above T(c) is not necessary to explain the existence of the quasiparticle interference at low energy.

  View details for DOI 10.1103/PhysRevLett.106.167003

  View details for Web of Science ID 000290097500013

  View details for PubMedID 21599403

• From a Single-Band Metal to a High-Temperature Superconductor via Two Thermal Phase Transitions SCIENCE He, R., Hashimoto, M., Karapetyan, H., Koralek, J. D., Hinton, J. P., Testaud, J. P., Nathan, V., Yoshida, Y., Yao, H., Tanaka, K., Meevasana, W., Moore, R. G., Lu, D. H., Mo, S., Ishikado, M., Eisaki, H., Hussain, Z., Devereaux, T. P., Kivelson, S. A., Orenstein, J., Kapitulnik, A., Shen, Z. 2011; 331 (6024): 1579-1583

  Abstract

  The nature of the pseudogap phase of cuprate high-temperature superconductors is a major unsolved problem in condensed matter physics. We studied the commencement of the pseudogap state at temperature T* using three different techniques (angle-resolved photoemission spectroscopy, polar Kerr effect, and time-resolved reflectivity) on the same optimally doped Bi2201 crystals. We observed the coincident, abrupt onset at T* of a particle-hole asymmetric antinodal gap in the electronic spectrum, a Kerr rotation in the reflected light polarization, and a change in the ultrafast relaxational dynamics, consistent with a phase transition. Upon further cooling, spectroscopic signatures of superconductivity begin to grow close to the superconducting transition temperature (T(c)), entangled in an energy-momentum-dependent manner with the preexisting pseudogap features, ushering in a ground state with coexisting orders.

  View details for DOI 10.1126/science.1198415

  View details for PubMedID 21436447

• Quantum Hall Effect from the Topological Surface States of Strained Bulk HgTe PHYSICAL REVIEW LETTERS Bruene, C., Liu, C. X., Novik, E. G., Hankiewicz, E. M., Buhmann, H., Chen, Y. L., Qi, X. L., Shen, Z. X., Zhang, S. C., Molenkamp, L. W. 2011; 106 (12)

  Abstract

  We report transport studies on a three-dimensional, 70-nm-thick HgTe layer, which is strained by epitaxial growth on a CdTe substrate. The strain induces a band gap in the otherwise semimetallic HgTe, which thus becomes a three-dimensional topological insulator. Contributions from residual bulk carriers to the transport properties of the gapped HgTe layer are negligible at mK temperatures. As a result, the sample exhibits a quantized Hall effect that results from the 2D single cone Dirac-like topological surface states.

  View details for DOI 10.1103/PhysRevLett.106.126803

  View details for Web of Science ID 000288651800009

  View details for PubMedID 21517339

• Cryogenic microwave imaging of metal-insulator transition in doped silicon REVIEW OF SCIENTIFIC INSTRUMENTS Kundhikanjana, W., Lai, K., Kelly, M. A., Shen, Z. 2011; 82 (3)

  Abstract

  We report the instrumentation and experimental results of a cryogenic scanning microwave impedance microscope. The microwave probe and the scanning stage are located inside the variable temperature insert of a helium cryostat. Microwave signals in the distance modulation mode are used for monitoring the tip-sample distance and adjusting the phase of the two output channels. The ability to spatially resolve the metal-insulator transition in a doped silicon sample is demonstrated. The data agree with a semiquantitative finite element simulation. Effects of the thermal energy and electric fields on local charge carriers can be seen in the images taken at different temperatures and dc biases.

  View details for DOI 10.1063/1.3554438

  View details for Web of Science ID 000289149600040

  View details for PubMedID 21456749

• Creation and control of a two-dimensional electron liquid at the bare SrTiO3 surface NATURE MATERIALS Meevasana, W., King, P. D., He, R. H., Mo, S., Hashimoto, M., Tamai, A., Songsiriritthigul, P., Baumberger, F., Shen, Z. 2011; 10 (2): 114-118

  Abstract

  Many-body interactions in transition-metal oxides give rise to a wide range of functional properties, such as high-temperature superconductivity, colossal magnetoresistance or multiferroicity . The seminal recent discovery of a two-dimensional electron gas (2DEG) at the interface of the insulating oxides LaAlO(3) and SrTiO(3) (ref. 4) represents an important milestone towards exploiting such properties in all-oxide devices. This conducting interface shows a number of appealing properties, including a high electron mobility, superconductivity and large magnetoresistance, and can be patterned on the few-nanometre length scale. However, the microscopic origin of the interface 2DEG is poorly understood. Here, we show that a similar 2DEG, with an electron density as large as 8×10(13)  cm(-2), can be formed at the bare SrTiO(3) surface. Furthermore, we find that the 2DEG density can be controlled through exposure of the surface to intense ultraviolet light. Subsequent angle-resolved photoemission spectroscopy measurements reveal an unusual coexistence of a light quasiparticle mass and signatures of strong many-body interactions.

  View details for DOI 10.1038/nmat2943

  View details for Web of Science ID 000286512200017

  View details for PubMedID 21240289

• Doping dependence of the (pi, pi) shadow band in La-based cuprates studied by angle-resolved photoemission spectroscopy NEW JOURNAL OF PHYSICS He, R., Zhou, X. J., Hashimoto, M., Yoshida, T., Tanaka, K., Mo, S., Sasagawa, T., Mannella, N., Meevasana, W., Yao, H., Fujita, M., Adachi, T., Komiya, S., Uchida, S., Ando, Y., Zhou, F., Zhao, Z. X., Fujimori, A., Koike, Y., Yamada, K., Hussain, Z., Shen, Z. 2011; 13

  View details for DOI 10.1088/1367-2630/13/1/013031

  View details for Web of Science ID 000288903600031

• Time-resolved Fermi surface mapping and dynamics of the double-CDW transition in HoTe3 Verhandlungen der Deutschen Physikalischen Gesellschaft Rettig, L., Cortes, R., Chu, J., Fisher, I., Schmitt, F., Kirchmann, P., Shen, Z., Wolf, M., Bovensiepen, U. 2011; 43 (5)
• A SHIELDED CANTILEVER-TIP MICROWAVE PROBE FOR MICRO/NANO SURFACE IMAGING OF CONDUCTIVE PROPERTIES Yang, Y. L., Lai, K. J., Tang, Q. C., Kundhikanjana, W., Kelly, M., Shen, Z. X., Li, X., IEEE IEEE. 2011: 79–82

  View details for DOI 10.1109/icra.2011.5980377

  View details for Web of Science ID 000295841200020

• Emerging Properties of Quantum Matter-Case Studies of Topological and Superconducting Phases ANL (Argonne National Laboratory Shen, Z. 2011
• The pseudogap phase in Bi2201 studied by ARPES The 26th International Conference on Low Temperature Physics Hashimoto, M., Tanaka, K., Meevasana, W., Moore, R., Lu, D., Mo, S., Ishikado, M., Eisaki, H., Hussain, Z., Devereaux, T., Kivelson, S., He, R., Orenstein, J., Kapitulnik, A., Shen, Z., Karapetyan, H., Koralek, J., Hinton, J., Testaud, J., Nathan, V., Yoshida, Y., Yao, H. 2011: 328–29
• Single Dirac Cone Topological Surface State and Unusual Thermoelectric Property of Compounds from a New Topological Insulator Family PHYSICAL REVIEW LETTERS Chen, Y. L., Liu, Z. K., Analytis, J. G., Chu, J., Zhang, H. J., Yan, B. H., Mo, S., Moore, R. G., Lu, D. H., Fisher, I. R., Zhang, S. C., Hussain, Z., Shen, Z. 2010; 105 (26)

  Abstract

  Angle resolved photoemission spectroscopy study on TlBiTe2 and TlBiSe2 from a thallium-based ternary chalcogenides family revealed a single surface Dirac cone at the center of the Brillouin zone for both compounds. For TlBiSe2, the large bulk gap (∼200 meV) makes it a topological insulator with better mechanical properties than the previous binary 3D topological insualtor family. For TlBiTe2, the observed negative bulk gap indicates it as a semimetal, instead of a narrow-gap semiconductor as conventionally believed; this semimetality naturally explains its mysteriously small thermoelectric figure of merit comparing to other compounds in the family. Finally, the unique band structures of TlBiTe2 also suggest it as a candidate for topological superconductors.

  View details for DOI 10.1103/PhysRevLett.105.266401

  View details for Web of Science ID 000286754700014

  View details for PubMedID 21231687

• Angle-resolved photoemission study of the tri-layer high-T-c superconductor Bi2Sr2Ca2Cu3O10+delta: Effects of inter-layer hopping 9th International Conference on Materials and Mechanisms of Superconductivity Ideta, S., Takashima, K., Hashimoto, M., Yoshida, T., Fujimori, A., Anzai, H., Fujita, T., Nakashima, Y., Ino, A., Arita, M., Namatame, H., Taniguchi, M., Ono, K., Kubota, M., Lu, D. H., Shen, Z., Kojima, K. M., Uchida, S. ELSEVIER SCIENCE BV. 2010: S14–S16

  View details for DOI 10.1016/j.physc.2009.10.152

  View details for Web of Science ID 000286075700006

• CORRELATED ELECTRON SYSTEMS Reaching for the stars NATURE MATERIALS Balents, L., Shen, Z. 2010; 9 (12): 963–64

  View details for DOI 10.1038/nmat2907

  View details for Web of Science ID 000284525300013

  View details for PubMedID 21102514

• Energy-Dependent Enhancement of the Electron-Coupling Spectrum of the Underdoped Bi2Sr2CaCu2O8+delta Superconductor PHYSICAL REVIEW LETTERS Anzai, H., Ino, A., Kamo, T., Fujita, T., Arita, M., Namatame, H., Taniguchi, M., Fujimori, A., Shen, Z., Ishikado, M., Uchida, S. 2010; 105 (22)

  Abstract

  We have determined the electron-coupling spectrum of superconducting Bi2Sr2CaCu2O(8+δ) from high-resolution angle-resolved photoemission spectra by two deconvolution-free robust methods. As hole concentration decreases, the coupling spectral weight at low energies ≲15  meV shows a twofold and nearly band-independent enhancement, while that around ∼65  meV increases moderately, and that in ≳130  meV decreases leading to a crossover of dominant coupling excitation between them. Our results suggest the competition among multiple screening effects, and provide important clues to the source of sufficiently strong low-energy coupling, λ(LE)≈1, in an underdoped system.

  View details for DOI 10.1103/PhysRevLett.105.227002

  View details for Web of Science ID 000286731000020

  View details for PubMedID 21231415

• ARPES studies of cuprate Fermiology: superconductivity, pseudogap and quasiparticle dynamics NEW JOURNAL OF PHYSICS Vishik, I. M., Lee, W. S., He, R., Hashimoto, M., Hussain, Z., Devereaux, T. P., Shen, Z. 2010; 12

  View details for DOI 10.1088/1367-2630/12/10/105008

  View details for Web of Science ID 000284770500004

• Surface and bulk electronic structures of LaFeAsO studied by angle-resolved photoemission spectroscopy PHYSICAL REVIEW B Yang, L. X., Xie, B. P., Zhang, Y., He, C., Ge, Q. Q., Wang, X. F., Chen, X. H., Arita, M., Jiang, J., Shimada, K., Taniguchi, M., Vobornik, I., Rossi, G., Hu, J. P., Lu, D. H., Shen, Z. X., Lu, Z. Y., Feng, D. L. 2010; 82 (10)

  View details for DOI 10.1103/PhysRevB.82.104519

  View details for Web of Science ID 000282123000004

• Photon-enhanced thermionic emission for solar concentrator systems NATURE MATERIALS Schwede, J. W., Bargatin, I., Riley, D. C., Hardin, B. E., Rosenthal, S. J., Sun, Y., Schmitt, F., Pianetta, P., Howe, R. T., Shen, Z., Melosh, N. A. 2010; 9 (9): 762-767

  Abstract

  Solar-energy conversion usually takes one of two forms: the 'quantum' approach, which uses the large per-photon energy of solar radiation to excite electrons, as in photovoltaic cells, or the 'thermal' approach, which uses concentrated sunlight as a thermal-energy source to indirectly produce electricity using a heat engine. Here we present a new concept for solar electricity generation, photon-enhanced thermionic emission, which combines quantum and thermal mechanisms into a single physical process. The device is based on thermionic emission of photoexcited electrons from a semiconductor cathode at high temperature. Temperature-dependent photoemission-yield measurements from GaN show strong evidence for photon-enhanced thermionic emission, and calculated efficiencies for idealized devices can exceed the theoretical limits of single-junction photovoltaic cells. The proposed solar converter would operate at temperatures exceeding 200 degrees C, enabling its waste heat to be used to power a secondary thermal engine, boosting theoretical combined conversion efficiencies above 50%.

  View details for DOI 10.1038/NMAT2814

  View details for Web of Science ID 000281178400029

  View details for PubMedID 20676086

• Systematic study of electron-phonon coupling to oxygen modes across the cuprates PHYSICAL REVIEW B Johnston, S., Vernay, F., Moritz, B., Shen, Z., Nagaosa, N., Zaanen, J., Devereaux, T. P. 2010; 82 (6)

  View details for DOI 10.1103/PhysRevB.82.064513

  View details for Web of Science ID 000281016800003

• Massive Dirac Fermion on the Surface of a Magnetically Doped Topological Insulator SCIENCE Chen, Y. L., Chu, J., Analytis, J. G., Liu, Z. K., Igarashi, K., Kuo, H., Qi, X. L., Mo, S. K., Moore, R. G., Lu, D. H., Hashimoto, M., Sasagawa, T., Zhang, S. C., Fisher, I. R., Hussain, Z., Shen, Z. X. 2010; 329 (5992): 659-662

  Abstract

  In addition to a bulk energy gap, topological insulators accommodate a conducting, linearly dispersed Dirac surface state. This state is predicted to become massive if time reversal symmetry is broken, and to become insulating if the Fermi energy is positioned inside both the surface and bulk gaps. We introduced magnetic dopants into the three-dimensional topological insulator dibismuth triselenide (Bi2Se3) to break the time reversal symmetry and further position the Fermi energy inside the gaps by simultaneous magnetic and charge doping. The resulting insulating massive Dirac fermion state, which we observed by angle-resolved photoemission, paves the way for studying a range of topological phenomena relevant to both condensed matter and particle physics.

  View details for DOI 10.1126/science.1189924

  View details for Web of Science ID 000280602700032

  View details for PubMedID 20689013

• Ultrathin Topological Insulator Bi2Se3 Nanoribbons Exfoliated by Atomic Force Microscopy NANO LETTERS Hong, S. S., Kundhikanjana, W., Cha, J. J., Lai, K., Kong, D., Meister, S., Kelly, M. A., Shen, Z., Cui, Y. 2010; 10 (8): 3118-3122

  Abstract

  Ultrathin topological insulator nanostructures, in which coupling between top and bottom surface states takes place, are of great intellectual and practical importance. Due to the weak van der Waals interaction between adjacent quintuple layers (QLs), the layered bismuth selenide (Bi(2)Se(3)), a single Dirac-cone topological insulator with a large bulk gap, can be exfoliated down to a few QLs. In this paper, we report the first controlled mechanical exfoliation of Bi(2)Se(3) nanoribbons (>50 QLs) by an atomic force microscope (AFM) tip down to a single QL. Microwave impedance microscopy is employed to map out the local conductivity of such ultrathin nanoribbons, showing drastic difference in sheet resistance between 1-2 QLs and 4-5 QLs. Transport measurement carried out on an exfoliated (50 QLs) ribbons. These AFM-exfoliated thin nanoribbons afford interesting candidates for studying the transition from quantum spin Hall surface to edge states.

  View details for DOI 10.1021/nl1018E4h

  View details for PubMedID 20698625

• Mesoscopic Percolating Resistance Network in a Strained Manganite Thin Film SCIENCE Lai, K., Nakamura, M., Kundhikanjana, W., Kawasaki, M., Tokura, Y., Kelly, M. A., Shen, Z. 2010; 329 (5988): 190-193

  Abstract

  Many unusual behaviors in complex oxides are deeply associated with the spontaneous emergence of microscopic phase separation. Depending on the underlying mechanism, the competing phases can form ordered or random patterns at vastly different length scales. By using a microwave impedance microscope, we observed an orientation-ordered percolating network in strained Nd(1/2)Sr(1/2)MnO3 thin films with a large period of 100 nanometers. The filamentary metallic domains align preferentially along certain crystal axes of the substrate, suggesting the anisotropic elastic strain as the key interaction in this system. The local impedance maps provide microscopic electrical information of the hysteretic behavior in strained thin film manganites, suggesting close connection between the glassy order and the colossal magnetoresistance effects at low temperatures.

  View details for DOI 10.1126/science.1189925

  View details for Web of Science ID 000279635200041

  View details for PubMedID 20616272

• Particle-hole symmetry breaking in the pseudogap state of Bi2201 NATURE PHYSICS Hashimoto, M., He, R., Tanaka, K., Testaud, J., Meevasana, W., Moore, R. G., Lu, D., Yao, H., Yoshida, Y., Eisaki, H., Devereaux, T. P., Hussain, Z., Shen, Z. 2010; 6 (6): 414-418

  View details for DOI 10.1038/NPHYS1632

  View details for Web of Science ID 000279014400011

• Enhanced Superconducting Gaps in the Trilayer High-Temperature Bi2Sr2Ca2Cu3O10+delta Cuprate Superconductor PHYSICAL REVIEW LETTERS Ideta, S., Takashima, K., Hashimoto, M., Yoshida, T., Fujimori, A., Anzai, H., Fujita, T., Nakashima, Y., Ino, A., Arita, M., Namatame, H., Taniguchi, M., Ono, K., Kubota, M., Lu, D. H., Shen, Z., Kojima, K. M., Uchida, S. 2010; 104 (22)

  Abstract

  We report the first observation of the multilayer band splitting in the optimally doped trilayer cuprate Bi2Sr2Ca2Cu3O(10+δ) (Bi2223) by angle-resolved photoemission spectroscopy. The observed energy bands and Fermi surfaces are originated from the outer and inner CuO2 planes (OP and IP). The OP band is overdoped with a large d-wave gap around the node of Δ0∼43  meV while the IP is underdoped with an even large gap of Δ0∼60  meV. These energy gaps are much larger than those for the same doping level of the double-layer cuprates, which leads to the large Tc in Bi2223. We propose possible origins of the large superconducting gaps for the OP and IP: (1) minimal influence of out-of-plane disorder and a proximity effect and (2) interlayer tunneling of Cooper pairs between the OP and IP.

  View details for DOI 10.1103/PhysRevLett.104.227001

  View details for Web of Science ID 000278207500024

  View details for PubMedID 20867198

• Doping-Dependent Nodal Fermi Velocity of the High-Temperature Superconductor Bi2Sr2CaCu2O8+delta Revealed Using High-Resolution Angle-Resolved Photoemission Spectroscopy PHYSICAL REVIEW LETTERS Vishik, I. M., Lee, W. S., Schmitt, F., Moritz, B., Sasagawa, T., Uchida, S., Fujita, K., Ishida, S., Zhang, C., Devereaux, T. P., Shen, Z. X. 2010; 104 (20)

  Abstract

  The improved resolution of laser-based angle-resolved photoemission spectroscopy (ARPES) allows reliable access to fine structures in the spectrum. We present a systematic, doping-dependent study of a recently discovered low-energy kink in the nodal dispersion of Bi2Sr2CaCu2O(8+δ) (Bi-2212), which demonstrates the ubiquity and robustness of this kink in underdoped Bi-2212. The renormalization of the nodal velocity due to this kink becomes stronger with underdoping, revealing that the nodal Fermi velocity is nonuniversal, in contrast with assumed phenomenology. This is used together with laser ARPES measurements of the gap velocity (v2) to resolve discrepancies with thermal conductivity measurements.

  View details for DOI 10.1103/PhysRevLett.104.207002

  View details for Web of Science ID 000277945900042

  View details for PubMedID 20867053

• Signatures of pressure-induced superconductivity in insulating Bi1.98Sr2.06Y0.68CaCu2O8+delta PHYSICAL REVIEW B Cuk, T., Zocco, D. A., Eisaki, H., Struzhkin, V., Grosche, F. M., Maple, M. B., Shen, Z. 2010; 81 (18)

  View details for DOI 10.1103/PhysRevB.81.184509

  View details for Web of Science ID 000278141800088

• Aharonov-Bohm interference in topological insulator nanoribbons NATURE MATERIALS Peng, H., Lai, K., Kong, D., Meister, S., Chen, Y., Qi, X., Zhang, S., Shen, Z., Cui, Y. 2010; 9 (3): 225-229

  Abstract

  Topological insulators represent unusual phases of quantum matter with an insulating bulk gap and gapless edges or surface states. The two-dimensional topological insulator phase was predicted in HgTe quantum wells and confirmed by transport measurements. Recently, Bi(2)Se(3) and related materials have been proposed as three-dimensional topological insulators with a single Dirac cone on the surface, protected by time-reversal symmetry. The topological surface states have been observed by angle-resolved photoemission spectroscopy experiments. However, few transport measurements in this context have been reported, presumably owing to the predominance of bulk carriers from crystal defects or thermal excitations. Here we show unambiguous transport evidence of topological surface states through periodic quantum interference effects in layered single-crystalline Bi(2)Se(3) nanoribbons, which have larger surface-to-volume ratios than bulk materials and can therefore manifest surface effects. Pronounced Aharonov-Bohm oscillations in the magnetoresistance clearly demonstrate the coherent propagation of two-dimensional electrons around the perimeter of the nanoribbon surface, as expected from the topological nature of the surface states. The dominance of the primary h/e oscillation, where h is Planck's constant and e is the electron charge, and its temperature dependence demonstrate the robustness of these states. Our results suggest that topological insulator nanoribbons afford promising materials for future spintronic devices at room temperature.

  View details for DOI 10.1038/NMAT2609

  View details for Web of Science ID 000274700900017

  View details for PubMedID 20010826

• Evolution of electronic structure from insulator to superconductor in Bi2Sr2-xLax(Ca,Y)Cu2O8+delta PHYSICAL REVIEW B Tanaka, K., Yoshida, T., Shen, K. M., Lu, D. H., Lee, W. S., Yagi, H., Fujimori, A., Shen, Z., Risdiana, R., Fujii, T., Terasaki, I. 2010; 81 (12)

  View details for DOI 10.1103/PhysRevB.81.125115

  View details for Web of Science ID 000276248900052

• Strong energy-momentum dispersion of phonon-dressed carriers in the lightly doped band insulator SrTiO3 NEW JOURNAL OF PHYSICS Meevasana, W., Zhou, X. J., Moritz, B., Chen, C., He, R. H., Fujimori, S., Lu, D. H., Mo, S., Moore, R. G., Baumberger, F., Devereaux, T. P., van der Marel, D., Nagaosa, N., Zaanen, J., Shen, Z. 2010; 12

  View details for DOI 10.1088/1367-2630/12/2/023004

  View details for Web of Science ID 000274247300004

• Environmentally Friendly Refining of Diamond-Molecules via the Growth of Large Single Crystals CRYSTAL GROWTH & DESIGN Iwasa, A., Clay, W. A., Dahl, J. E., Carlson, R. M., Shen, Z., Sasagawa, T. 2010; 10 (2): 870-873

  View details for DOI 10.1021/cg901218t

  View details for Web of Science ID 000274837000056

• Fermi surface evolution across multiple charge density wave transitions in ErTe3 PHYSICAL REVIEW B Moore, R. G., Brouet, V., He, R., Lu, D. H., Ru, N., Chu, J., Fisher, I. R., Shen, Z. 2010; 81 (7)

  View details for DOI 10.1103/PhysRevB.81.073102

  View details for Web of Science ID 000274998200002

• STM Imaging of Electronic Waves on the Surface of Bi2Te3: Topologically Protected Surface States and Hexagonal Warping Effects PHYSICAL REVIEW LETTERS Alpichshev, Z., Analytis, J. G., Chu, J., Fisher, I. R., Chen, Y. L., Shen, Z. X., Fang, A., Kapitulnik, A. 2010; 104 (1)

  Abstract

  Scanning tunneling spectroscopy studies on high-quality Bi2Te3 crystals exhibit perfect correspondence to angle-resolved photoemission spectroscopy data, hence enabling identification of different regimes measured in the local density of states (LDOS). Oscillations of LDOS near a step are analyzed. Within the main part of the surface band oscillations are strongly damped, supporting the hypothesis of topological protection. At higher energies, as the surface band becomes concave, oscillations appear, dispersing with a wave vector that may result from a hexagonal warping term.

  View details for DOI 10.1103/PhysRevLett.104.016401

  View details for Web of Science ID 000273881900022

  View details for PubMedID 20366373

• Topological Insulator Nanowires and Nanoribbons NANO LETTERS Kong, D., Randel, J. C., Peng, H., Cha, J. J., Meister, S., Lai, K., Chen, Y., Shen, Z., Manoharan, H. C., Cui, Y. 2010; 10 (1): 329-333

  Abstract

  Recent theoretical calculations and photoemission spectroscopy measurements on the bulk Bi(2)Se(3) material show that it is a three-dimensional topological insulator possessing conductive surface states with nondegenerate spins, attractive for dissipationless electronics and spintronics applications. Nanoscale topological insulator materials have a large surface-to-volume ratio that can manifest the conductive surface states and are promising candidates for devices. Here we report the synthesis and characterization of high quality single crystalline Bi(2)Se(3) nanomaterials with a variety of morphologies. The synthesis of Bi(2)Se(3) nanowires and nanoribbons employs Au-catalyzed vapor-liquid-solid (VLS) mechanism. Nanowires, which exhibit rough surfaces, are formed by stacking nanoplatelets along the axial direction of the wires. Nanoribbons are grown along [1120] direction with a rectangular cross-section and have diverse morphologies, including quasi-one-dimensional, sheetlike, zigzag and sawtooth shapes. Scanning tunneling microscopy (STM) studies on nanoribbons show atomically smooth surfaces with approximately 1 nm step edges, indicating single Se-Bi-Se-Bi-Se quintuple layers. STM measurements reveal a honeycomb atomic lattice, suggesting that the STM tip couples not only to the top Se atomic layer, but also to the Bi atomic layer underneath, which opens up the possibility to investigate the contribution of different atomic orbitals to the topological surface states. Transport measurements of a single nanoribbon device (four terminal resistance and Hall resistance) show great promise for nanoribbons as candidates to study topological surface states.

  View details for DOI 10.1021/nl903663a

  View details for Web of Science ID 000273428700055

  View details for PubMedID 20030392

• LUMO photoemission lineshape in quasi-one-dimensional C-60 chains PHYSICAL REVIEW B Tamai, A., Baumberger, F., Hengsberger, M., Lobo-Checa, J., Muntwiler, M., Corso, M., Cirelli, C., Patthey, L., Shen, Z., Greber, T., Osterwalder, J. 2010; 81 (4)

  View details for DOI 10.1103/PhysRevB.81.045423

  View details for Web of Science ID 000274002500105

• Bulk Fermi Surface Co-existence with Dirac Surface State in Bi2Se3: A Comparison of Photoemission and Shubnikov-de Haas Measurements Physical Review B Analytis, J. G., Chu, J., Chen, Y., Corredor, F., McDonald, R. D., Shen, Z., Fisher, I. R. 2010; 81 (20)

  View details for DOI 10.1103/PhysRevB.81.205407

• Material and Doping Dependence of the Nodal and Antinodal Dispersion Renormalizations in Single- and Multilayer Cuprates ADVANCES IN CONDENSED MATTER PHYSICS Johnston, S., Lee, W. S., Chen, Y., Nowadnick, E. A., Moritz, B., Shen, Z., Devereaux, T. P. 2010

  View details for DOI 10.1155/2010/968304

  View details for Web of Science ID 000294023600001

• Zn-impurity effects on quasiparticle scattering in La2-xSrxCuO4 studied by angle-resolved photoemission spectroscopy PHYSICAL REVIEW B Yoshida, T., Komiya, S., Zhou, X. J., Tanaka, K., Fujimori, A., Hussain, Z., Shen, Z., Ando, Y., Eisaki, H., Uchida, S. 2009; 80 (24)

  View details for DOI 10.1103/PhysRevB.80.245113

  View details for Web of Science ID 000273229200057

• Hierarchy of Electronic Properties of Chemically Derived and Pristine Graphene Probed by Microwave Imaging NANO LETTERS Kundhikanjana, W., Lai, K., Wang, H., Dai, H., Kelly, M. A., Shen, Z. 2009; 9 (11): 3762-3765

  Abstract

  Local electrical imaging using microwave impedance microscope is performed on graphene in different modalities, yielding a rich hierarchy of the local conductivity. The low-conductivity graphite oxide and its derivatives show significant electronic inhomogeneity. For the conductive chemical graphene, the residual defects lead to a systematic reduction of the microwave signals. In contrast, the signals on pristine graphene agree well with a lumped-element circuit model. The local impedance information can also be used to verify the electrical contact between overlapped graphene pieces.

  View details for DOI 10.1021/nl901949z

  View details for PubMedID 19678669

• Unconventional electronic reconstruction in undoped (Ba,Sr)Fe2As2 across the spin density wave transition PHYSICAL REVIEW B Yi, M., Lu, D. H., Analytis, J. G., Chu, J., Mo, S., He, R., Hashimoto, M., Moore, R. G., Mazin, I. I., Singh, D. J., Hussain, Z., Fisher, I. R., Shen, Z. 2009; 80 (17)

  View details for DOI 10.1103/PhysRevB.80.174510

  View details for Web of Science ID 000272310400081

• A momentum-dependent perspective on quasiparticle interference in Bi2Sr2CaCu2O8+delta NATURE PHYSICS Vishik, I. M., Nowadnick, E. A., Lee, W. S., Shen, Z. X., Moritz, B., Devereaux, T. P., Tanaka, K., Sasagawa, T., Fujii, T. 2009; 5 (10): 718-721

  View details for DOI 10.1038/NPHYS1375

  View details for Web of Science ID 000271185400010

• Effect of strong correlations on the high energy anomaly in hole- and electron-doped high-T-c superconductors NEW JOURNAL OF PHYSICS Moritz, B., Schmitt, F., Meevasana, W., Johnston, S., Motoyama, E. M., Greven, M., Lu, D. H., Kim, C., Scalettar, R. T., Shen, Z., Devereaux, T. P. 2009; 11

  View details for DOI 10.1088/1367-2630/11/9/093020

  View details for Web of Science ID 000269819000006

• Dependence of Band-Renormalization Effects on the Number of Copper Oxide Layers in Tl-Based Copper Oxide Superconductors Revealed by Angle-Resolved Photoemission Spectroscopy PHYSICAL REVIEW LETTERS Lee, W. S., Tanaka, K., Vishik, I. M., Lu, D. H., Moore, R. G., Eisaki, H., Iyo, A., Devereaux, T. P., Shen, Z. X. 2009; 103 (6)

  Abstract

  Here we report the first angle-resolved photoemission measurement on nearly optimally doped multilayer Tl-based superconducting cuprates (Tl-2212 and Tl-1223) and a comparison study to single-layer (Tl-2201) compound. A "kink" in the band dispersion is found in all three compounds but exhibits different momentum dependence for the single-layer and multilayer compounds, reminiscent to that of Bi-based cuprates. This layer number dependent renormalization effect strongly implies that the spin-resonance mode is unlikely to be responsible for the dramatic renormalization effect near the antinodal region.

  View details for DOI 10.1103/PhysRevLett.103.067003

  View details for Web of Science ID 000268809300056

  View details for PubMedID 19792598

• Underlying Fermi surface of Sr14-xCaxCu24O41 in two-dimensional momentum space observed by angle-resolved photoemission spectroscopy PHYSICAL REVIEW B Yoshida, T., Zhou, X. J., Hussain, Z., Shen, Z., Fujimori, A., Eisaki, H., Uchida, S. 2009; 80 (5)

  View details for DOI 10.1103/PhysRevB.80.052504

  View details for Web of Science ID 000269638500016

• Universal versus Material-Dependent Two-Gap Behaviors of the High-T-c Cuprate Superconductors: Angle-Resolved Photoemission Study of La2-xSrxCuO4 PHYSICAL REVIEW LETTERS Yoshida, T., Hashimoto, M., Ideta, S., Fujimori, A., Tanaka, K., Mannella, N., Hussain, Z., Shen, Z., Kubota, M., Ono, K., Komiya, S., Ando, Y., Eisaki, H., Uchida, S. 2009; 103 (3)

  Abstract

  We have investigated the doping and temperature dependences of the pseudogap and superconducting gap in the single-layer cuprate La2-xSrxCuO4 by angle-resolved photoemission spectroscopy. The results clearly exhibit two distinct energy and temperature scales, namely, the gap around (pi, 0) of magnitude Delta* and the gap around the node characterized by the d-wave order parameter Delta0. In comparison with Bi2212 having higher Tc's, Delta0 is smaller, while Delta* and T* are similar. This result suggests that Delta* and T* are approximately material-independent properties of a single CuO2 plane, in contrast to the material-dependent Delta0, representing the pairing strength.

  View details for DOI 10.1103/PhysRevLett.103.037004

  View details for Web of Science ID 000268088300057

  View details for PubMedID 19659310

• Unusual Layer-Dependent Charge Distribution, Collective Mode Coupling, and Superconductivity in Multilayer Cuprate Ba2Ca3Cu4O8F2 PHYSICAL REVIEW LETTERS Chen, Y., Iyo, A., Yang, W., Ino, A., Arita, M., Johnston, S., Eisaki, H., Namatame, H., Taniguchi, M., Devereaux, T. P., Hussain, Z., Shen, Z. 2009; 103 (3)

  Abstract

  Low energy ultrahigh momentum resolution angle resolved photoemission spectroscopy study on four-layer self-doped high Tc superconductor Ba2Ca3Cu4O8F2 (F0234) revealed fine structure in the band dispersion, identifying the unconventional association of hole and electron doping with the inner and outer CuO2 layers, respectively. For the states originating from two inequivalent CuO2 layers, different energy scales are observed in dispersion kinks associated with the collective mode coupling, with the larger energy scale found in the electron (n-) doped state which also has stronger coupling strength. Given the earlier finding that the superconducting gap is substantially larger along the n-type Fermi surface, our observations connect the mode coupling energy and strength with magnitude of the pairing gap.

  View details for DOI 10.1103/PhysRevLett.103.036403

  View details for Web of Science ID 000268088300048

  View details for PubMedID 19659301

• Experimental Realization of a Three-Dimensional Topological Insulator, Bi2Te3 SCIENCE Chen, Y. L., Analytis, J. G., Chu, J., Liu, Z. K., Mo, S., Qi, X. L., Zhang, H. J., Lu, D. H., Dai, X., Fang, Z., Zhang, S. C., Fisher, I. R., Hussain, Z., Shen, Z. 2009; 325 (5937): 178-181

  Abstract

  Three-dimensional topological insulators are a new state of quantum matter with a bulk gap and odd number of relativistic Dirac fermions on the surface. By investigating the surface state of Bi2Te3 with angle-resolved photoemission spectroscopy, we demonstrate that the surface state consists of a single nondegenerate Dirac cone. Furthermore, with appropriate hole doping, the Fermi level can be tuned to intersect only the surface states, indicating a full energy gap for the bulk states. Our results establish that Bi2Te3 is a simple model system for the three-dimensional topological insulator with a single Dirac cone on the surface. The large bulk gap of Bi2Te3 also points to promising potential for high-temperature spintronics applications.

  View details for DOI 10.1126/science.1173034

  View details for Web of Science ID 000267802000040

  View details for PubMedID 19520912

• Electronic structure of the BaFe2As2 family of iron-pnictide superconductors PHYSICAL REVIEW B Yi, M., Lu, D. H., Analytis, J. G., Chu, J., Mo, S., He, R., Moore, R. G., Zhou, X. J., Chen, G. F., Luo, J. L., Wang, N. L., Hussain, Z., Singh, D. J., Fisher, I. R., Shen, Z. 2009; 80 (2)

  View details for DOI 10.1103/PhysRevB.80.024515

  View details for Web of Science ID 000268617500094

• Evidence for weak electronic correlations in iron pnictides PHYSICAL REVIEW B Yang, W. L., Sorini, A. P., Chen, C., Moritz, B., Lee, W., Vernay, F., Olalde-Velasco, P., Denlinger, J. D., Delley, B., Chu, J., Analytis, J. G., Fisher, I. R., Ren, Z. A., Yang, J., Lu, W., Zhao, Z. X., van den Brink, J., Hussain, Z., Shen, Z., Devereaux, T. P. 2009; 80 (1)

  View details for DOI 10.1103/PhysRevB.80.014508

  View details for Web of Science ID 000268617100099

• ARPES studies of the electronic structure of LaOFe(P, As) PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS Lu, D. H., Yi, M., Mo, S., Analytis, J. G., Chu, J., Erickson, A. S., Singh, D. J., Hussain, Z., Geballe, T. H., Fisher, I. R., Shen, Z. 2009; 469 (9-12): 452-458

  View details for DOI 10.1016/j.physc.2009.03.044

  View details for Web of Science ID 000267191500018

• A brief update of angle-resolved photoemission spectroscopy on a correlated electron system 25th International Conference on Low Temperature Physics (LT25) Lee, W. S., Vishik, I. M., Lu, D. H., Shen, Z. IOP PUBLISHING LTD. 2009

  Abstract

  In this paper, we briefly summarize the capabilities of state-of-the-art angle-resolved photoemission spectroscopy (ARPES) in the field of experimental condensed matter physics. Due to the advancement of the detector technology and the high flux light sources, ARPES has become a powerful tool to study the low energy excitations of solids, especially those novel quantum materials in which many-body physics are at play. To benchmark today's state-of-the-art ARPES technique, we demonstrate that the precision of today's ARPES has advanced to a regime comparable to the bulk-sensitive de Haas-van Alphen (dHvA) measurements. Finally, as an example of new discoveries driven by the advancement of the ARPES technique, we summarize some of our recent ARPES measurements on underdoped high-T(c) superconducting cuprates, which have provided further insight into the complex pseudogap problem.

  View details for DOI 10.1088/0953-8984/21/16/164217

  View details for Web of Science ID 000264746900020

  View details for PubMedID 21825397

• Tapping mode microwave impedance microscopy REVIEW OF SCIENTIFIC INSTRUMENTS Lai, K., Kundhikanjana, W., Peng, H., Cui, Y., Kelly, M. A., Shen, Z. X. 2009; 80 (4)

  Abstract

  We report tapping mode microwave impedance imaging based on atomic force microscope platforms. The shielded cantilever probe is critical to localize the tip-sample interaction near the tip apex. The modulated tip-sample impedance can be accurately simulated by the finite-element analysis and the result agrees quantitatively to the experimental data on a series of thin-film dielectric samples. The tapping mode microwave imaging is also superior to the contact mode in that the thermal drift in a long time scale is totally eliminated and an absolute measurement on the dielectric properties is possible. We demonstrated tapping images on working nanodevices, and the data are consistent with the transport results.

  View details for DOI 10.1063/1.3123406

  View details for Web of Science ID 000266597100023

  View details for PubMedID 19405666

• Effects of out-of-plane disorder on the nodal quasiparticle and superconducting gap in single-layer Bi2Sr1.6L0.4CuO6+delta (L=La,Nd,Gd) PHYSICAL REVIEW B Hashimoto, M., Yoshida, T., Fujimori, A., Lu, D. H., Shen, Z., Kubota, M., Ono, K., Ishikado, M., Fujita, K., Uchida, S. 2009; 79 (14)

  View details for DOI 10.1103/PhysRevB.79.144517

  View details for Web of Science ID 000265943200114

• Nanoscale Electronic Inhomogeneity in In2Se3 Nanoribbons Revealed by Microwave Impedance Microscopy NANO LETTERS Lai, K., Peng, H., Kundhikanjana, W., Schoen, D. T., Xie, C., Meister, S., Cui, Y., Kelly, M. A., Shen, Z. 2009; 9 (3): 1265-1269

  Abstract

  Driven by interactions due to the charge, spin, orbital, and lattice degrees of freedom, nanoscale inhomogeneity has emerged as a new theme for materials with novel properties near multiphase boundaries. As vividly demonstrated in complex metal oxides (see refs 1-5) and chalcogenides (see refs 6 and 7), these microscopic phases are of great scientific and technological importance for research in high-temperature superconductors (see refs 1 and 2), colossal magnetoresistance effect (see ref 4), phase-change memories (see refs 5 and 6), and domain switching operations (see refs 7-9). Direct imaging on dielectric properties of these local phases, however, presents a big challenge for existing scanning probe techniques. Here, we report the observation of electronic inhomogeneity in indium selenide (In(2)Se(3)) nanoribbons (see ref 10) by near-field scanning microwave impedance microscopy (see refs 11-13). Multiple phases with local resistivity spanning 6 orders of magnitude are identified as the coexistence of superlattice, simple hexagonal lattice and amorphous structures with approximately 100 nm inhomogeneous length scale, consistent with high-resolution transmission electron microscope studies. The atomic-force-microscope-compatible microwave probe is able to perform a quantitative subsurface electrical study in a noninvasive manner. Finally, the phase change memory function in In(2)Se(3) nanoribbon devices can be locally recorded with big signals of opposite signs.

  View details for DOI 10.1021/nl900222j

  View details for Web of Science ID 000264142100060

• Energy gaps in the failed high-T-c superconductor La1:875Ba0:125CuO4 NATURE PHYSICS He, R., Tanaka, K., Mo, S., Sasagawa, T., Fujita, M., Adachi, T., Mannella, N., Yamada, K., Koike, Y., Hussain, Z., Shen, Z. 2009; 5 (2): 119-123

  View details for DOI 10.1038/NPHYS1159

  View details for Web of Science ID 000263458500015

• A step closer to visualizing the electron-phonon interplay in real time PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Chen, Y. L., Lee, W. S., Shen, Z. X. 2009; 106 (4): 963-964

  View details for DOI 10.1073/pnas.0812286106

  View details for Web of Science ID 000262831600001

  View details for PubMedID 19164546

  View details for PubMedCentralID PMC2633531

• Intrinsic electron and hole bands in electron-doped cuprate superconductors PHYSICAL REVIEW B Xiang, T., Luo, H. G., Lu, D. H., Shen, K. M., Shen, Z. X. 2009; 79 (1)

  View details for DOI 10.1103/PhysRevB.79.014524

  View details for Web of Science ID 000262977900112

• Bogoliubov angle, particle-hole mixture, and angle-resolved photoemission spectroscopy in superconductors PHYSICAL REVIEW B Balatsky, A. V., Lee, W. S., Shen, Z. X. 2009; 79 (2)

  View details for DOI 10.1103/PhysRevB.79.020505

  View details for Web of Science ID 000262978100019

• Thermionic emission from microfabricated silicon-carbide filaments Power MEMS Lee, J., Bargatin, I., Provine, J., Clay, W., Schwede, J., Liu, F., Maboudian, R., Melosh, N., Shen, Z., Howe, R. 2009: 1-4
• Origin of the Monochromatic Photoemission Peak in Diamondoid Monolayers NANO LETTERS Clay, W. A., Liu, Z., Yang, W., Fabbri, J. D., Dahl, J. E., Carlson, R. M., Sun, Y., Schreiner, P. R., Fokin, A. A., Tkachenko, B. A., Fokina, N. A., Pianetta, P. A., Melosh, N., Shen, Z. 2009; 9 (1): 57-61

  Abstract

  Recent photoemission experiments have discovered a highly monochromatized secondary electron peak emitted from diamondoid self-assembled monolayers on metal substrates. New experimental data and simulation results are presented to show that a combination of negative electron affinity and strong electron-phonon scattering is responsible for this behavior. The simulation results are generated using a simple Monte Carlo transport algorithm. The simulated spectra recreate the main spectral features of the measured ones.

  View details for DOI 10.1021/nl802310k

  View details for Web of Science ID 000262519100010

  View details for PubMedID 18975993

• Rare earth ion effects on the pseudo-gap in electron-doped superconductors and possible nodeless d-wave gap 61st Yamada Conference on Spectroscopies in Novel Superconductors Park, S. R., Leem, C. S., Roh, Y. S., Choi, K. J., Kim, J. H., Kim, B. J., Koh, H., Eisaki, H., Lu, D. H., Shen, Z., Armitage, N. P., Kim, C. PERGAMON-ELSEVIER SCIENCE LTD. 2008: 2939–43

  View details for DOI 10.1016/j.jpcs.2008.06.116

  View details for Web of Science ID 000261971200005

• Diamondoids as low-kappa dielectric materials APPLIED PHYSICS LETTERS Clay, W. A., Sasagawa, T., Kelly, M., Dahl, J. E., Carlson, R. M., Melosh, N., Shen, Z. 2008; 93 (17)

  View details for DOI 10.1063/1.3010379

  View details for Web of Science ID 000260571800066

• A route to tunable direct band-gap diamond devices: Electronic structures of nanodiamond crystals JOURNAL OF APPLIED PHYSICS Sasagawa, T., Shen, Z. 2008; 104 (7)

  View details for DOI 10.1063/1.2986637

  View details for Web of Science ID 000260125500066

• Calibration of shielded microwave probes using bulk dielectrics APPLIED PHYSICS LETTERS Lai, K., Kundhikanjana, W., Kelly, M. A., Shen, Z. X. 2008; 93 (12)

  View details for DOI 10.1063/1.2990638

  View details for Web of Science ID 000259799100066

• Transient electronic structure and melting of a charge density wave in TbTe3 SCIENCE Schmitt, F., Kirchmann, P. S., Bovensiepen, U., Moore, R. G., Rettig, L., Krenz, M., Chu, J., Ru, N., Perfetti, L., Lu, D. H., Wolf, M., Fisher, I. R., Shen, Z. 2008; 321 (5896): 1649-1652

  Abstract

  Obtaining insight into microscopic cooperative effects is a fascinating topic in condensed matter research because, through self-coordination and collectivity, they can lead to instabilities with macroscopic impacts like phase transitions. We used femtosecond time- and angle-resolved photoelectron spectroscopy (trARPES) to optically pump and probe TbTe3, an excellent model system with which to study these effects. We drove a transient charge density wave melting, excited collective vibrations in TbTe3, and observed them through their time-, frequency-, and momentum-dependent influence on the electronic structure. We were able to identify the role of the observed collective vibration in the transition and to document the transition in real time. The information that we demonstrate as being accessible with trARPES will greatly enhance the understanding of all materials exhibiting collective phenomena.

  View details for DOI 10.1126/science.1160778

  View details for Web of Science ID 000259300400026

  View details for PubMedID 18703710

• Electronic structure of the iron-based superconductor LaOFeP NATURE Lu, D. H., Yi, M., Mo, S., Erickson, A. S., Analytis, J., Chu, J., Singh, D. J., Hussain, Z., Geballe, T. H., Fisher, I. R., Shen, Z. 2008; 455 (7209): 81-84

  Abstract

  The recent discovery of superconductivity in the iron oxypnictide family of compounds has generated intense interest. The layered crystal structure with transition-metal ions in planar square-lattice form and the discovery of spin-density-wave order near 130 K (refs 10, 11) seem to hint at a strong similarity with the copper oxide superconductors. An important current issue is the nature of the ground state of the parent compounds. Two distinct classes of theories, distinguished by the underlying band structure, have been put forward: a local-moment antiferromagnetic ground state in the strong-coupling approach, and an itinerant ground state in the weak-coupling approach. The first approach stresses on-site correlations, proximity to a Mott-insulating state and, thus, the resemblance to the high-transition-temperature copper oxides, whereas the second approach emphasizes the itinerant-electron physics and the interplay between the competing ferromagnetic and antiferromagnetic fluctuations. The debate over the two approaches is partly due to the lack of conclusive experimental information on the electronic structures. Here we report angle-resolved photoemission spectroscopy (ARPES) of LaOFeP (superconducting transition temperature, T(c) = 5.9 K), the first-reported iron-based superconductor. Our results favour the itinerant ground state, albeit with band renormalization. In addition, our data reveal important differences between these and copper-based superconductors.

  View details for DOI 10.1038/nature07263

  View details for Web of Science ID 000258890200040

  View details for PubMedID 18769435

• Analysis of the spectral function of Nd1.85Ce0.15CuO4 obtained by angle-resolved photoemission spectroscopy PHYSICAL REVIEW B Schmitt, F., Lee, W. S., Lu, D., Meevasana, W., Motoyama, E., Greven, M., Shen, Z. 2008; 78 (10)

  View details for DOI 10.1103/PhysRevB.78.100505

  View details for Web of Science ID 000259690400015

• Appearance of universal metallic dispersion in a doped Mott insulator PHYSICAL REVIEW B Sahrakorpi, S., Markiewicz, R. S., Lin, H., Lindroos, M., Zhou, X. J., Yoshida, T., Yang, W. L., Kakeshita, T., Eisaki, H., Uchida, S., Komiya, S., Ando, Y., Zhou, F., Zhao, Z. X., Sasagawa, T., Fujimori, A., Hussain, Z., Shen, Z., Bansil, A. 2008; 78 (10)

  View details for DOI 10.1103/PhysRevB.78.104513

  View details for Web of Science ID 000259690400089

• Modeling and characterization of a cantilever-based near-field scanning microwave impedance microscope REVIEW OF SCIENTIFIC INSTRUMENTS Lai, K., Kundhikanjana, W., Kelly, M., Shen, Z. X. 2008; 79 (6)

  Abstract

  This paper presents a detailed modeling and characterization of a microfabricated cantilever-based scanning microwave probe with separated excitation and sensing electrodes. Using finite-element analysis, we model the tip-sample interaction as small impedance changes between the tip electrode and the ground at our working frequencies near 1 GHz. The equivalent lumped elements of the cantilever can be determined by transmission line simulation of the matching network, which routes the cantilever signals to 50 Omega feed lines. In the microwave electronics, the background common-mode signal is canceled before the amplifier stage so that high sensitivity (below 1 aF capacitance changes) is obtained. Experimental characterization of the microwave microscope was performed on ion-implanted Si wafers and patterned semiconductor samples. Pure electrical or topographical signals can be obtained from different reflection modes of the probe.

  View details for DOI 10.1063/1.2949109

  View details for Web of Science ID 000257283700020

  View details for PubMedID 18601409

• Uncovering a pressure-tuned electronic transition in Bi1.98Sr2.06Y0.68Cu2O8+delta using Raman scattering and x-ray diffraction PHYSICAL REVIEW LETTERS Cuk, T., Struzhkin, V. V., Devereaux, T. P., Goncharov, A. F., Kendziora, C. A., Eisaki, H., Mao, H., Shen, Z. 2008; 100 (21)

  Abstract

  We report pressure-tuned Raman and x-ray diffraction data of Bi(1.98.)Sr(2.06)Y(0.68)Cu(2)O(8+delta) revealing a critical pressure at 21 GPa with anomalies in electronic Raman background, electron-phonon coupling lambda, spectral weight transfer, density dependent behavior of phonons and magnons, and a compressibility change in the c axis. For the first time in a cuprate, mobile charge carriers, lattice, and magnetism all show anomalies at a distinct critical pressure in the same experimental setting. Furthermore, the spectral changes suggest that the critical pressure at 21 GPa is related to the critical point at optimal doping.

  View details for DOI 10.1103/PhysRevLett.100.217003

  View details for Web of Science ID 000256585500042

  View details for PubMedID 18518627

• Superconductivity-induced self-energy evolution of the nodal electron of optimally doped Bi2Sr2Ca0.92Y0.08Cu2O8+delta PHYSICAL REVIEW B Lee, W. S., Meevasana, W., Johnston, S., Lu, D. H., Vishik, I. M., Moore, R. G., Eisaki, H., Kaneko, N., Devereaux, T. P., Shen, Z. X. 2008; 77 (14)

  View details for DOI 10.1103/PhysRevB.77.140504

  View details for Web of Science ID 000255457300008

• Extracting the spectral function of the cuprates by a full two-dimensional analysis: Angle-resolved photoemission spectra of Bi2Sr2CuO6 PHYSICAL REVIEW B Meevasana, W., Baumberger, F., Tanaka, K., Schmitt, F., Dunkel, W. R., Lu, D. H., Mo, S., Eisaki, H., Shen, Z. 2008; 77 (10)

  View details for DOI 10.1103/PhysRevB.77.104506

  View details for Web of Science ID 000254542700102

• Direct evidence of two gaps in underdoped Bi2212 International Symposium on Lattice Effects in Cuprate High Temperature Superconductors Tanaka, K., Lee, W. S., Hussain, Z., Shen, Z. X. IOP PUBLISHING LTD. 2008

  View details for DOI 10.1088/1742-6596/108/1/012014

  View details for Web of Science ID 000261516600014

• Fermi surface and van hove singularities in the itinerant metamagnet Sr3Ru2O7 PHYSICAL REVIEW LETTERS Tamai, A., Allan, M., Mercure, J., Meevasana, W., Dunkel, R., Lu, D., Perry, R., Mackenzie, A., Singh, D., Shen, Z., Baumberger, F. 2008; 101 (2)

  View details for DOI 10.1103/PhysRevLett.101.026407

• Superconductivity: Brings About Real Resonance Nature Physics Lee, W., Shen, Z. 2008; 4 (2): 95-96

  View details for DOI 10.1038/nphys849

• Electronic Structure at the C60/Metal Interface: An angle-resolved photoemission and first principle study PHYSICAL REVIEW B Tamai, A., Seitsonen, A., Baumberger, F., Hengsberger, M., Shen, Z., Greber, T., Osterwalder, J. 2008; 77 (7)

  View details for DOI 10.1103/PhysRevB.77.075134

• Doping Evolution of the Electronic Structure in the Single-Layer Cuprates Bi2Sr2-xLaxCuO6+d: Comparison with Other Single-Layer Cuprates PHYSICAL REVIEW B Hashimoto, M., Yoshida, T., Yagi, H., Takizawa, M., Fujimori, A., Kubota, M., Ono, K., Tanaka, K., Lu, D., Shen, Z., Ono, S., Ando, Y. 2008; 77 (9)
• Charge Dynamics of Doped Holes in High-Tc Cuprates – A Clue from Optical Conductivity PHYSICAL REVIEW LETTERS Mishchenko, A., Nagaosa, N., Shen, Z., De Filippis, G., Cataudella, V., Devereaux, T., Bernhard, C., Kim, K., Zaanen, J. 2008; 100 (16)

  View details for DOI 10.1103/PhysRevLett.100.166401

• ARPES Study of the Evolution of Band Structure and Charge Density Wave Properties in Rte3 for R = Y, La, Ce, Sm, Gd, Tb and Dy Physical Review B Hussain, Z., Brouet, V., Yang, W., Zhou, X., Moore, R., He, R., Lu, D., Shen, Z., Laverock, J., Dugdale, S., Ru, N., Fisher, R. 2008; 77 (235104)
• A route to tunable direct band-gap diamond devices: Electronic structure of nanodiamond crystals Journal of applied physics Sasagawa, T., Shen, Z. 2008; 104 (7): 073704
• Scientific Needs for Future X-ray Sources in the US--A White Paper Lawrence Berkeley National Lab.(LBNL) Falcone, R., Stohr, J., Bergmann, U., Corlett, J., Galayda, J., Hastings, J., Hettel, B., Hussain, Z., Kirz, J., McCurdy, B., Raubernheimer, T., Sannibale, F., Seeman, J., Shen, Z., Schoenlein, B., Zholents, A. 2008
• Polaron coherence condensation as the mechanism for colossal magnetoresistance in layered manganites PHYSICAL REVIEW B Mannella, N., Yang, W. L., Tanaka, K., Zhou, X. J., Zheng, H., Mitchell, J. F., Zaanen, J., Devereaux, T. P., Nagaosa, N., Hussain, Z., Shen, Z. 2007; 76 (23)

  View details for DOI 10.1103/PhysRevB.76.233102

  View details for Web of Science ID 000251986500002

• Complete momentum and energy resolved TOF electron spectrometer for time-resolved photoemission spectroscopy 14th National Conference on Synchrotron Radiation Instrumentation Lebedev, G., Tremsin, A., Siegmund, O., Chen, Y., Shen, Z., Hussain, Z. ELSEVIER SCIENCE BV. 2007: 168–71

  View details for DOI 10.1016/j.nima.2007.08.099

  View details for Web of Science ID 000251039500052

• Design of an elliptically bent refocus mirror for the MERLIN beamline at the advanced light source 14th National Conference on Synchrotron Radiation Instrumentation Kelez, N., Chuang, Y., Smith-Baumann, A., Franck, K., Duarte, R., Lanzara, A., Hasan, M. Z., Dessau, D. S., Chiang, T. C., Shen, Z., Hussain, Z. ELSEVIER SCIENCE BV. 2007: 135–37

  View details for DOI 10.1016/j.nima.2007.08.092

  View details for Web of Science ID 000251039500042

• Evolution of the fermi surface and quasiparticle renormalization through a van hove singularity in Sr2-yLayRuO4 PHYSICAL REVIEW LETTERS Shen, K. M., Kikugawa, N., Bergemann, C., Balicas, L., Baumberger, F., Meevasana, W., Ingle, N. J., Maeno, Y., Shen, Z., Mackenzie, A. P. 2007; 99 (18)

  Abstract

  We employ a combination of chemical substitution and angle resolved photoemission spectroscopy to prove that the Fermi level in the gamma band of Sr(2-y)La(y)RuO(4) can be made to traverse a van Hove singularity. Remarkably, the large mass renormalization has little dependence on either k or doping. By combining the results from photoemission with thermodynamic measurements on the same batches of crystals, we deduce a parametrization of the full many-body quasiparticle dispersion in Sr(2)RuO(4) which extends from the Fermi level to approximately 20 meV above it.

  View details for DOI 10.1103/PhysRevLett.99.187001

  View details for Web of Science ID 000250644000045

  View details for PubMedID 17995427

• Abrupt onset of a second energy gap at the superconducting transition of underdoped Bi2212 NATURE Lee, W. S., Vishik, I. M., Tanaka, K., Lu, D. H., Sasagawa, T., Nagaosa, N., Devereaux, T. P., Hussain, Z., Shen, Z. 2007; 450 (7166): 81-84

  Abstract

  The superconducting gap--an energy scale tied to the superconducting phenomena--opens on the Fermi surface at the superconducting transition temperature (T(c)) in conventional BCS superconductors. In underdoped high-T(c) superconducting copper oxides, a pseudogap (whose relation to the superconducting gap remains a mystery) develops well above T(c) (refs 1, 2). Whether the pseudogap is a distinct phenomenon or the incoherent continuation of the superconducting gap above T(c) is one of the central questions in high-T(c) research. Although some experimental evidence suggests that the two gaps are distinct, this issue is still under intense debate. A crucial piece of evidence to firmly establish this two-gap picture is still missing: a direct and unambiguous observation of a single-particle gap tied to the superconducting transition as function of temperature. Here we report the discovery of such an energy gap in underdoped Bi2Sr2CaCu2O8+delta in the momentum space region overlooked in previous measurements. Near the diagonal of Cu-O bond direction (nodal direction), we found a gap that opens at T(c) and has a canonical (BCS-like) temperature dependence accompanied by the appearance of the so-called Bogoliubov quasi-particles, a classical signature of superconductivity. This is in sharp contrast to the pseudogap near the Cu-O bond direction (antinodal region) measured in earlier experiments.

  View details for DOI 10.1038/nature06219

  View details for Web of Science ID 000250585800040

  View details for PubMedID 17972881

• High spatial and temporal resolution photon/electron counting detector for synchrotron radiation research 3rd International Conference on Imaging Techniques in Subatomic Physics, Astrophysics, Medicine, Biology and Industry Tremsin, A. S., LEBEDEV, G. V., Siegmund, O. H., Vallerga, J. V., Hull, J. S., McPhate, J. B., Jozwiak, C., Chen, Y., Guo, J. H., Shen, Z. X., Hussain, Z. ELSEVIER SCIENCE BV. 2007: 853–57

  View details for DOI 10.1016/j.nima.2007.06.085

  View details for Web of Science ID 000250128000006

• Effects of Zn-impurity scattering in La2-xSrxCuO4 studied by angle-resolved photoemission spectroscopy 8th International Conference on Materials and Mechanisms of Superconductivity and High Temperature Superconductors Yoshida, T., Zhou, X. J., Hussain, Z., Shen, Z. X., Fujimori, A., Komiya, S., Ando, Y., Eisaki, H., Uchinda, S. ELSEVIER SCIENCE BV. 2007: 872–873

  View details for DOI 10.1016/j.physc.2007.03.095

  View details for Web of Science ID 000249870600074

• Existence of a quasiparticle remnant in angle-resolved photoemission spectrum of La2-xSrxCuO4 8th International Conference on Materials and Mechanisms of Superconductivity and High Temperature Superconductors Lindroos, M., Arpiainen, V., Sahrakorpi, S., Markiewicz, R. S., Zhou, X. J., Yoshida, T., Yang, W. L., Kakeshita, T., Eisaki, H., Uchida, S., Fujimori, A., Hussain, Z., Shen, Z., Bansil, A. ELSEVIER SCIENCE BV. 2007: 941–942

  View details for DOI 10.1016/j.physc.2007.03.358

  View details for Web of Science ID 000249870600105

• Electronic band structure and Kondo coupling in YbRh2Si2 PHYSICAL REVIEW B Wigger, G. A., Baumberger, F., Shen, Z., Yin, Z. P., Pickett, W. E., Maquilon, S., Fisk, Z. 2007; 76 (3)

  View details for DOI 10.1103/PhysRevB.76.035106

  View details for Web of Science ID 000248500800039

• Monochromatic electron photoemission from diamondoid monolayers SCIENCE Yang, W. L., Fabbri, J. D., Willey, T. M., Lee, J. R., Dahl, J. E., Carlson, R. M., Schreiner, P. R., Fokin, A. A., Tkachenko, B. A., Fokina, N. A., Meevasana, W., Mannella, N., Tanaka, K., Zhou, X. J., van Buuren, T., Kelly, M. A., Hussain, Z., Melosh, N. A., Shen, Z. 2007; 316 (5830): 1460-1462

  Abstract

  We found monochromatic electron photoemission from large-area self-assembled monolayers of a functionalized diamondoid, [121]tetramantane-6-thiol. Photoelectron spectra of the diamondoid monolayers exhibited a peak at the low-kinetic energy threshold; up to 68% of all emitted electrons were emitted within this single energy peak. The intensity of the emission peak is indicative of diamondoids being negative electron affinity materials. With an energy distribution width of less than 0.5 electron volts, this source of monochromatic electrons may find application in technologies such as electron microscopy, electron beam lithography, and field-emission flat-panel displays.

  View details for DOI 10.1126/science.1141811

  View details for PubMedID 17556579

• Atomic-force-microscope-compatible near-field scanning microwave microscope with separated excitation and sensing probes REVIEW OF SCIENTIFIC INSTRUMENTS Lai, K., Ji, M. B., Leindecker, N., Kelly, M. A., Shen, Z. X. 2007; 78 (6)

  Abstract

  We present the design and experimental results of a near-field scanning microwave microscope working at a frequency of 1 GHz. Our microscope is unique in that the sensing probe is separated from the excitation electrode to significantly suppress the common-mode signal. Coplanar waveguides were patterned onto a silicon nitride cantilever interchangeable with atomic force microscope tips, which are robust for high speed scanning. In the contact mode that we are currently using, the numerical analysis shows that contrast comes from both the variation in local dielectric properties and the sample topography. Our microscope demonstrates the ability to achieve high resolution microwave images on buried structures, as well as nanoparticles, nanowires, and biological samples.

  View details for DOI 10.1063/1.2746768

  View details for Web of Science ID 000247626200014

  View details for PubMedID 17614611

• Hierarchy of multiple many-body interaction scales in high-temperature superconductors PHYSICAL REVIEW B Meevasana, W., Zhou, X. J., Sahrakorpi, S., Lee, W. S., Yang, W. L., Tanaka, K., Mannella, N., Yoshida, T., Lu, D. H., Chen, Y. L., He, R. H., Lin, H., Komiya, S., Ando, Y., Zhou, F., Ti, W. X., Xiong, J. W., Zhao, Z. X., Sasagawa, T., Kakeshita, T., Fujita, K., Uchida, S., Eisaki, H., Fujimori, A., Hussain, Z., Markiewicz, R. S., Bansil, A., Nagaosa, N., Zaanen, J., Devereaux, T. P., Shen, Z. 2007; 75 (17)

  View details for DOI 10.1103/PhysRevB.75.174506

  View details for Web of Science ID 000246890500119

• Aspects of electron-phonon self-energy revealed from angle-resolved photoemission spectroscopy PHYSICAL REVIEW B Lee, W. S., Johnston, S., Devereaux, T. P., Shen, Z. 2007; 75 (19)

  View details for DOI 10.1103/PhysRevB.75.195116

  View details for Web of Science ID 000246890800045

• Unmasking the nodal quasiparticle dynamics in cuprate superconductors using low-energy photoemission PHYSICAL REVIEW B Yamasaki, T., Yamazaki, K., Ino, A., Arita, M., Namatame, H., Taniguchi, M., Fujimori, A., Shen, Z., Ishikado, M., Uchida, S. 2007; 75 (14)

  View details for DOI 10.1103/PhysRevB.75.140513

  View details for Web of Science ID 000246075100024

• Ca3Ru2O7: Electronic instability and extremely strong quasiparticle renormalisation 17th International Conference on Magnetism (ICM 2006) Kikugawa, N., Rost, A., Baumberger, F., Ingle, N. J., Hossain, M. A., Meevasana, W., Shen, K. M., Lu, D. H., Damascelli, A., Mackenzie, A. P., Hussain, Z., Shen, Z. X. ELSEVIER SCIENCE BV. 2007: 1027–29

  View details for DOI 10.1016/j.jmmm.2006.10.225

  View details for Web of Science ID 000247618700161

• Hybridization of 4f states in heavy-fermion compounds YbRh2Si2 and YbIr2Si2 17th International Conference on Magnetism (ICM 2006) Molodtsov, S. L., Danzenbaecher, S., Kucherenko, Y., Laubschat, C., Vyalikh, D. V., Hossain, Z., Geibel, C., Zhou, X. J., Yang, W. L., Mannella, N., Hussain, Z., Shen, Z., Shi, M., Patthey, L. ELSEVIER SCIENCE BV. 2007: 443–45

  View details for DOI 10.1016/j.jmmm.2006.10.501

  View details for Web of Science ID 000247666000088

• Angle-resolved photoemission studies of lattice polaron formation in the cuprate Ca2CuO2Cl2 PHYSICAL REVIEW B Shen, K. M., Ronning, F., Meevasana, W., Lu, D. H., Ingle, N. J., Baumberger, F., Lee, W. S., MILLER, L. L., Kohsaka, Y., Azuma, M., Takano, M., Takagi, H., Shen, Z. 2007; 75 (7)

  View details for DOI 10.1103/PhysRevB.75.075115

  View details for Web of Science ID 000244533400044

• Doping Evolution of the Cuprate Superconductors from High Resolution ARPES Very High Resolution Photoelectron Spectroscopy Shen, K., Shen, Z. Springer, Berlin, Heidelberg. 2007: 243–270

  View details for DOI https://doi.org/10.1007/3-540-68133-7_9

• Insights from ARPES for an undoped, four-layered, two gap high-Tc superconductor Physical review letters Xie, W., Jepsen, O., Andersen, O., Chen, Y., Shen, Z. 2007; 98 (4): 047001
• Angle-Resolved Photoemission Spectroscopy on Electronic Structure and lectron–Phonon Coupling in Cuprate Superconductors Handbook of High-Temperature Superconductivity Zhou, X., Cuk, T., Devereaux, T., Nagaosa, N., Shen, Z. Springer, New York, NY. 2007: 87–144
• Momentum dependence of 4f hybridization in heavy-fermion compounds: Angle-resolved photoemission study of YbIr2Si2 and YbRh2Si2 PHYSICAL REVIEW B Danzenbaecher, S., Kucherenko, Y., Vyalikh, D. V., Holder, M., Laubschat, C., Yaresko, A. N., Krellner, C., Hossain, Z., Geibel, C., Zhou, X. J., Yang, W. L., Mannella, N., Hussain, Z., Shen, Z., Shi, M., Patthey, L., Molodtsov, S. L. 2007; 75 (4)

  View details for DOI 10.1103/PhysRevB.75.045109

  View details for Web of Science ID 000243895600026

• Band Renormalization Effect in Bi2Sr2Ca2Cu3O10 δ High Tc Superconductors and Related Transition Metal Oxides Lee, W., Cuk, T., Meevasane, W., Lu, D., Shen, K., Shen, Z., Yang, W., Zhou, X., Hussain, Z., Shimoyama, J., Devereaux, T. 2007
• Low-energy electronic structure of the high-Tc cuprates La2− xSrxCuO4 studied by angle-resolved photoemission spectroscopy Journal of Physics: Condensed Matter Yoshida, Y., Zhou, X., Lu, D., Komiya, S., Ando, Y., Eisaki, H., Kakeshita, T., Uchida, S., Hussain, Z., Shen, Z., Fujimori, A. 2007; 19 (12)
• Distinct Fermi-momentum-dependent energy gaps in deeply underdoped Bi2212 SCIENCE Tanaka, K., Lee, W. S., Lu, D. H., Fujimori, A., Fujii, T., Risdiana, Terasaki, I., Scalapino, D. J., Devereaux, T. P., Hussain, Z., Shen, Z. 2006; 314 (5807): 1910-1913

  Abstract

  We used angle-resolved photoemission spectroscopy applied to deeply underdoped cuprate superconductors Bi2Sr2Ca(1-x)YxCu2O8 (Bi2212) to reveal the presence of two distinct energy gaps exhibiting different doping dependence. One gap, associated with the antinodal region where no coherent peak is observed, increased with underdoping, a behavior known for more than a decade and considered as the general gap behavior in the underdoped regime. The other gap, associated with the near-nodal regime where a coherent peak in the spectrum can be observed, did not increase with less doping, a behavior not previously observed in the single particle spectra. We propose a two-gap scenario in momentum space that is consistent with other experiments and may contain important information on the mechanism of high-transition temperature superconductivity.

  View details for DOI 10.1126/science.1133411

  View details for Web of Science ID 000242996800043

  View details for PubMedID 17114172

• Anomalous Fermi-surface dependent pairing in a self-doped high-T-c superconductor PHYSICAL REVIEW LETTERS Chen, Y., Iyo, A., Yang, W., Zhou, X., Lu, D., Eisaki, H., Devereaux, T. P., Hussain, Z., Shen, Z. 2006; 97 (23)

  Abstract

  We report the discovery of a self-doped multilayer high Tc superconductor Ba2Ca3Cu4O8F2 (F0234) which contains distinctly different superconducting gap magnitudes along its two Fermi-surface sheets. While formal valence counting would imply this material to be an undoped insulator, it is a self-doped superconductor with a Tc of 60 K, possessing simultaneously both electron- and hole-doped Fermi-surface sheets. Intriguingly, the Fermi-surface sheet characterized by the much larger gap is the electron-doped one, which has a shape disfavoring two electronic features considered to be important for the pairing mechanism: the van Hove singularity and the antiferromagnetic (pi/a, pi/a) scattering.

  View details for DOI 10.1103/PhysRevLett.97.236401

  View details for Web of Science ID 000242708900037

  View details for PubMedID 17280217

• Systematic doping evolution of the underlying Fermi surface of La2-xSrxCuO4 PHYSICAL REVIEW B Yoshida, T., Zhou, X. J., Tanaka, K., Yang, W. L., Hussain, Z., Shen, Z., Fujimori, A., Sahrakorpi, S., Lindroos, M., Markiewicz, R. S., Bansil, A., Komiya, S., Ando, Y., Eisaki, H., Kakeshita, T., Uchida, S. 2006; 74 (22)

  View details for DOI 10.1103/PhysRevB.74.224510

  View details for Web of Science ID 000243195600095

• Calculation of overdamped c-axis charge dynamics and the coupling to polar phonons in cuprate superconductors PHYSICAL REVIEW B Meevasana, W., Devereaux, T. P., Nagaosa, N., Shen, Z., Zaanen, J. 2006; 74 (17)

  View details for DOI 10.1103/PhysRevB.74.174524

  View details for Web of Science ID 000242409000130

• Photoemission study of excess oxygen-doped La2CuO4.10 18th International Symposium on Superconductivity (ISS 2005) Hashimoto, M., Yoshida, T., Tanaka, K., Fujimori, A., Lu, D. H., Shen, Z. X., Wakimoto, S., Okusawa, M., Yamada, K. ELSEVIER SCIENCE BV. 2006: 80–83

  View details for DOI 10.1016/j.physc.2006.03.083

  View details for Web of Science ID 000240964100022

• Sr2RhO4: a new, clean correlated electron metal NEW JOURNAL OF PHYSICS Perry, R. S., Baumberger, F., Balicas, L., Kikugawa, N., Ingle, N. J., Rost, A., Mercure, J. F., Maeno, Y., Shen, Z. X., Mackenzie, A. P. 2006; 8

  View details for DOI 10.1088/1367-2630/8/9/175

  View details for Web of Science ID 000240237500005

• Angle-resolved photoemission spectroscopy of perovskite-type transition-metal oxides and their analyses using tight-binding band structure Indo-US Conference on Novel and Complex Materials Wadati, H., Yoshida, T., Chikamatsu, A., Kumigashira, H., Oshima, M., Eisaki, H., Shen, Z., Mizokawa, T., Fujimori, A. TAYLOR & FRANCIS LTD. 2006: 617–35

  View details for DOI 10.1080/01411590600826672

  View details for Web of Science ID 000241600800002

• Fermi surface and quasiparticle excitations of Sr2RhO4 PHYSICAL REVIEW LETTERS Baumberger, F., Ingle, N. J., Meevasana, W., Shen, K. M., Lu, D. H., Perry, R. S., Mackenzie, A. P., Hussain, Z., Singh, D. J., Shen, Z. 2006; 96 (24)

  Abstract

  The electronic structure of the layered 4d transition metal oxide Sr2RhO4 is investigated by angle resolved photoemission. We find well-defined quasiparticle excitations with a highly anisotropic dispersion, suggesting a quasi-two-dimensional Fermi-liquid-like ground state. Markedly different from the isostructural Sr2RuO4, only two bands with dominant Rh 4dxz,zy character contribute to the Fermi surface. A quantitative analysis of the photoemission quasiparticle band structure is in excellent agreement with bulk data. In contrast, it is found that state-of-the-art density functional calculations in the local density approximation differ significantly from the experimental findings.

  View details for DOI 10.1103/PhysRevLett.96.246402

  View details for Web of Science ID 000238487900041

  View details for PubMedID 16907260

• Distinct spinon and holon dispersions in photoemission spectral functions from one-dimensional SrCuO2 NATURE PHYSICS Kim, B. J., Koh, H., Rotenberg, E., Oh, S., Eisaki, H., Motoyama, N., Uchida, S., Tohyama, T., Maekawa, S., Shen, Z., Kim, C. 2006; 2 (6): 397-401

  View details for DOI 10.1038/nphys316

  View details for Web of Science ID 000238529600022

• Doping dependence of the coupling of electrons to bosonic modes in the single-layer high-temperature Bi2Sr2CuO6 superconductor PHYSICAL REVIEW LETTERS Meevasana, W., Ingle, N. J., Lu, D. H., Shi, J. R., Baumberger, F., Shen, K. M., Lee, W. S., Cuk, T., Eisaki, H., Devereaux, T. P., Nagaosa, N., Zaanen, J., Shen, Z. X. 2006; 96 (15)

  Abstract

  A recent highlight in the study of high-T(c) superconductors is the observation of band renormalization or self-energy effects on the quasiparticles. This is seen in the form of kinks in the quasiparticle dispersions as measured by photoemission and interpreted as signatures of collective bosonic modes coupling to the electrons. Here we compare for the first time the self-energies in an optimally doped and strongly overdoped, nonsuperconducting single-layer Bi-cuprate (Bi2Sr2CuO6). In addition to the appearance of a strong overall weakening, we also find that the weight of the self-energy in the overdoped system shifts to higher energies. We present evidence that this is related to a change in the coupling to c-axis phonons due to the rapid change of the c-axis screening in this doping range.

  View details for DOI 10.1103/PhysRevLett.96.157003

  View details for Web of Science ID 000236969700057

  View details for PubMedID 16712188

• Comment on "Multiple bosonic mode coupling in the electron self-energy of (La2-xSrx)CuO4" - Zhou et al. reply PHYSICAL REVIEW LETTERS Zhou, X. J., Shi, J. R., Yang, W. L., Komiya, S., Ando, Y., Plummer, W., Hussain, Z., Shen, Z. X. 2006; 96 (11)

  View details for DOI 10.1103/PhysRevLett.96.119702

  View details for Web of Science ID 000236249900086

• Nested Fermi surface and electronic instability in Ca3Ru2O7 PHYSICAL REVIEW LETTERS Baumberger, F., Ingle, N. J., Kikugawa, N., Hossain, M. A., Meevasana, W., Perry, R. S., Shen, K. M., Lu, D. H., Damascelli, A., Rost, A., Mackenzie, A. P., Hussain, Z., Shen, Z. X. 2006; 96 (10)

  Abstract

  High-resolution angular resolved photoemission data reveal well-defined quasiparticle bands of unusually low weight, emerging in line with the metallic phase of Ca(3)Ru(2)O(7) below approximately 30 K . At the bulk structural phase transition temperature of 48 K, we find clear evidence for an electronic instability, gapping large parts of the underlying Fermi surface that appears to be nested. Metallic pockets are found to survive in the small, non-nested sections, constituting a low-temperature Fermi surface with 2 orders of magnitude smaller volume than in all other metallic ruthenates. The Fermi velocities and volumes of these pockets are in agreement with the results of complementary quantum oscillation measurements on the same crystal batches.

  View details for DOI 10.1103/PhysRevLett.96.107601

  View details for Web of Science ID 000236062800079

  View details for PubMedID 16605788

• Energy dispersion of 4f-derived emissions in photoelectron spectra of the heavy-fermion compound YbIr2Si2 PHYSICAL REVIEW LETTERS Danzenbacher, S., Kucherenko, Y., Laubschat, C., Vyalikh, D. V., Hossain, Z., Geibel, C., Zhou, X. J., Yang, W. L., Mannella, N., Hussain, Z., Shen, Z. X., Molodtsov, S. L. 2006; 96 (10)

  Abstract

  Angle-resolved photoemission spectra of the heavy-fermion system YbIr(2)Si(2) are reported that reveal strong momentum (k) dependent splittings of the 4f(13) bulk and surface emissions around the expected intersection points of the 4f final states with valence bands in the Brillouin zone. The obtained dispersion is explained in terms of a simplified periodic Anderson model by a k dependence of the electron hopping matrix element disregarding clearly interpretation in terms of a single-impurity model.

  View details for DOI 10.1103/PhysRevLett.96.106402

  View details for Web of Science ID 000236062800060

  View details for PubMedID 16605769

• Puzzles about 1/8 magic doping in cuprate 7th International Conference on Spectroscopies in Novel Superconductors (SNS 04) Feng, D. L., Shen, Z. X., Zhou, X. J., Shen, K. M., Lu, D. H., van der Marel, D. PERGAMON-ELSEVIER SCIENCE LTD. 2006: 198–200

  View details for DOI 10.1016/j.jpcs.2005.10.149

  View details for Web of Science ID 000236746600050

• Dependence of the Band Structure of C60 Monolayers on Molecular Orientations and Doping Observed by Angle-Resolved Photoemission JOURNAL OF PHYSICS AND CHEMISTRY OF SOLID Brouet, V., Yang, W., Zhou, X., Hussain, Z., Shen, Z. 2006; 67 (1-3): 218-222

  View details for DOI 10.1016/j.jpcs.2005.10.170

• Systematic Doping Evolution of the Underlying Fermi Surface in La2-xSrxCuO4 PHYSICAL REVIEW B Yoshida, Y., Zhou, X., Tanaka, K., Yang, W., Hussain, Z., Shen, Z., Fujimori, A., Sahrakorpi, S., Lindroos, M., Markiewicz, R., Bansil, A., Komiya, S., Ando, Y., Eisaki, H., Kakeshita, T., Uchida, S. 2006; 74 (22)
• Normal state spectral lineshapes of nodal quasiparticles in single layer Bi2201 superconductor 7th International Conference on Spectroscopies in Novel Superconductors (SNS 04) Lanzara, A., Bogdanov, P. V., Zhou, X. J., Kaneko, N., Eisaki, H., Greven, M., Hussain, Z., Shen, Z. X. PERGAMON-ELSEVIER SCIENCE LTD. 2006: 239–43

  View details for DOI 10.1016/j.jpcs.2005.10.129

  View details for Web of Science ID 000236746600059

• Polaronic behavior of undoped high-T-c cuprate superconductors from angle-resolved photoemission spectra PHYSICAL REVIEW LETTERS Rosch, O., Gunnarsson, O., Zhou, X. J., Yoshida, T., Sasagawa, T., Fujimori, A., Hussain, Z., Shen, Z. X., Uchida, S. 2005; 95 (22)

  Abstract

  We present angle-resolved photoemission spectroscopy (ARPES) data on undoped La2CuO4, indicating polaronic coupling between bosons and charge carriers. Using a shell model, we calculate the electron-phonon coupling and find that it is strong enough to give self-trapped polarons. We develop an efficient method for calculating ARPES spectra in undoped systems. Using the calculated couplings, we find the width of the phonon sideband in good agreement with experiment. We analyze reasons for the observed dependence of the width on the binding energy.

  View details for DOI 10.1103/PhysRevLett.95.227002

  View details for Web of Science ID 000233458500059

  View details for PubMedID 16384255

• Nodal quasiparticle in pseudogapped colossal magnetoresistive manganites NATURE Mannella, N., Yang, W. L., Zhou, X. J., Zheng, H., Mitchell, J. F., Zaanen, J., Devereaux, T. P., Nagaosa, N., Hussain, Z., Shen, Z. X. 2005; 438 (7067): 474-478

  Abstract

  A characteristic feature of the copper oxide high-temperature superconductors is the dichotomy between the electronic excitations along the nodal (diagonal) and antinodal (parallel to the Cu-O bonds) directions in momentum space, generally assumed to be linked to the 'd-wave' symmetry of the superconducting state. Angle-resolved photoemission measurements in the superconducting state have revealed a quasiparticle spectrum with a d-wave gap structure that exhibits a maximum along the antinodal direction and vanishes along the nodal direction. Subsequent measurements have shown that, at low doping levels, this gap structure persists even in the high-temperature metallic state, although the nodal points of the superconducting state spread out in finite 'Fermi arcs'. This is the so-called pseudogap phase, and it has been assumed that it is closely linked to the superconducting state, either by assigning it to fluctuating superconductivity or by invoking orders which are natural competitors of d-wave superconductors. Here we report experimental evidence that a very similar pseudogap state with a nodal-antinodal dichotomous character exists in a system that is markedly different from a superconductor: the ferromagnetic metallic groundstate of the colossal magnetoresistive bilayer manganite La1.2Sr1.8Mn2O7. Our findings therefore cast doubt on the assumption that the pseudogap state in the copper oxides and the nodal-antinodal dichotomy are hallmarks of the superconductivity state.

  View details for DOI 10.1038/nature04273

  View details for Web of Science ID 000233458200044

  View details for PubMedID 16306987

• Quantitative analysis of Sr2RuO4 angle-resolved photoemission spectra: Many-body interactions in a model Fermi liquid PHYSICAL REVIEW B Ingle, N. J., Shen, K. M., Baumberger, F., Meevasana, W., Lu, D. H., Shen, Z. X., Damascelli, A., Nakatsuji, S., Mao, Z. Q., Maeno, Y., Kimura, T., Tokura, Y. 2005; 72 (20)

  View details for DOI 10.1103/PhysRevB.72.205114

  View details for Web of Science ID 000233603900030

• Direct observation of the mass renormalization in SrVO3 by angle resolved photoemission spectroscopy PHYSICAL REVIEW LETTERS Yoshida, T., Tanaka, K., Yagi, H., Ino, A., Eisaki, H., Fujimori, A., Shen, Z. X. 2005; 95 (14)

  Abstract

  Band dispersions and Fermi surfaces of the three-dimensional Mott-Hubbard system SrVO3 are directly observed by angle-resolved photoemission spectroscopy. An observed spectral weight distribution near the Fermi level (E(F)) shows cylindrical Fermi surfaces as predicted by band-structure calculations. By comparing the experimental results with calculated surface electronic structures, we conclude that the obtained band dispersion reflects the bulk electronic structure. The enhanced effective electron mass obtained from the energy band near E(F) is consistent with the bulk thermodynamic properties and hence with the normal Fermi-liquid behavior of SrVO3.

  View details for DOI 10.1103/PhysRevLett.95.146404

  View details for Web of Science ID 000232229800047

  View details for PubMedID 16241677

• Multiple bosonic mode coupling in the electron self-energy of (La2-xSrx)CuO4 PHYSICAL REVIEW LETTERS Zhou, X. J., Shi, J. R., Yoshida, T., Cuk, T., Yang, W. L., Brouet, V., Nakamura, J., Mannella, N., Komiya, S., Ando, Y., Zhou, F., Ti, W. X., Xiong, J. W., Zhao, Z. X., Sasagawa, T., Kakeshita, T., Eisaki, H., Uchida, S., Fujimori, A., Zhang, Z. Y., Plummer, E. W., Laughlin, R. B., Hussain, Z., Shen, Z. X. 2005; 95 (11)

  Abstract

  High resolution angle-resolved photoemission spectroscopy data along the (0,0)-(pi,pi) nodal direction with significantly improved statistics reveal fine structure in the electron self-energy of the underdoped (La2-xSrx)CuO4 samples in the normal state. Fine structure at energies of (40-46) meV and (58-63) meV, and possible fine structure at energies of (23-29) meV and (75-85) meV, have been identified. These observations indicate that, in (La2-xSrx)CuO4, more than one bosonic modes are involved in the coupling with electrons.

  View details for DOI 10.1103/PhysRevLett.95.117001

  View details for Web of Science ID 000231802000055

  View details for PubMedID 16197033

• Orientation-dependent C-60 electronic structures revealed by photoemission spectroscopy (vol 93, pg 197601, 2004) PHYSICAL REVIEW LETTERS Brouet, Yang, W. L., Zhou, X. J., Choi, H. J., Louie, S. G., Cohen, M. L., Goldoni, A., Parmigiani, F., Hussain, Z., Shen, Z. X. 2005; 95 (9)

  View details for DOI 10.1103/PhysRevLett.95.099903

  View details for Web of Science ID 000231503600082

• Doping-induced reorientation of C-60 molecules on Ag(111) PHYSICAL REVIEW B Tamai, A., Seitsonen, A. P., Fasel, R., Shen, Z. X., Osterwalder, J., Greber, T. 2005; 72 (8)

  View details for DOI 10.1103/PhysRevB.72.085421

  View details for Web of Science ID 000231564600148

• Quantitative measurement of sheet resistance by evanescent microwave probe APPLIED PHYSICS LETTERS Wang, Z. Y., Kelly, M. A., Shen, Z. X., Shao, L., Chu, W. K., Edwards, H. 2005; 86 (15)

  View details for DOI 10.1063/1.1891296

  View details for Web of Science ID 000228901600100

• Anomalous high-energy dispersion in angle-resolved photoemission spectra from the insulating cuprate Ca2CuO2Cl2 PHYSICAL REVIEW B Ronning, F., Shen, K. M., Armitage, N. P., Damascelli, A., Lu, D. H., Shen, Z. X., MILLER, L. L., Kim, C. 2005; 71 (9)

  View details for DOI 10.1103/PhysRevB.71.094518

  View details for Web of Science ID 000228727100109

• Nodal quasiparticles and antinodal charge ordering in Ca2-xNaxCuO2Cl2 SCIENCE Shen, K. M., Ronning, F., Lu, D. H., Baumberger, F., Ingle, N. J., Lee, W. S., Meevasana, W., Kohsaka, Y., Azuma, M., Takano, M., Takagi, H., Shen, Z. X. 2005; 307 (5711): 901-904

  Abstract

  Understanding the role of competing states in the cuprates is essential for developing a theory for high-temperature superconductivity. We report angle-resolved photoemission spectroscopy experiments which probe the 4a0 x 4a0 charge-ordered state discovered by scanning tunneling microscopy in the lightly doped cuprate superconductor Ca2-xNaxCuO2Cl2. Our measurements reveal a marked dichotomy between the real- and momentum-space probes, for which charge ordering is emphasized in the tunneling measurements and photoemission is most sensitive to excitations near the node of the d-wave superconducting gap. These results emphasize the importance of momentum anisotropy in determining the complex electronic properties of the cuprates and places strong constraints on theoretical models of the charge-ordered state.

  View details for DOI 10.1126/science.1103627

  View details for Web of Science ID 000226985100046

  View details for PubMedID 15705845

• Space charge effect and mirror charge effect in photoemission spectroscopy JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Zhou, X. J., WANNBERG, B., Yang, W. L., Brouet, V., Sun, Z., DOUGLAS, J. F., Dessau, D., Hussain, Z., Shen, Z. X. 2005; 142 (1): 27-38

  View details for DOI 10.1016/j.elspec.2004.08.004

  View details for Web of Science ID 000226496700002

• Quantitative analysis of Sr 2 RuO 4 angle-resolved photoemission spectra: Many-body interactions in a model Fermi liquid PHYSICAL REVIEW B Ingle, N., Shen, K., Baumberger, F., Meevasana, W., Lu, D., Shen, Z., Damascelli, A., Nakatsuji, S., Mao, Z., Maeno, Y., Kimura, T., Tokura, Y. 2005; 72 (205114)
• Electron-Phonon Coupling in High-Temperature Cuprate Superconductors as Revealed by Angle-Resolved Photoemission Spectroscopy Synchrotron Radiation News Zhou, X., Hussain, J., Shen, Z. 2005; 18 (3)
• Electronic structure and charge-density wave formation in La Te 1.95 and Ce Te 2.00 PHYSICAL REVIEW B Shin, K., Brouet, V., Ru, N., Shen, Z., Fisher, I. 2005; 72 (8)

  View details for DOI 10.1103/PhysRevB.72.085132

• Missing quasiparticles and the chemical potential puzzle in the doping evolution of the cuprate superconductors PHYSICAL REVIEW LETTERS Shen, K. M., Ronning, F., Lu, D. H., Lee, W. S., Ingle, N. J., Meevasana, W., Baumberger, F., Damascelli, A., Armitage, N. P., MILLER, L. L., Kohsaka, Y., Azuma, M., Takano, M., Takagi, H., Shen, Z. X. 2004; 93 (26)

  Abstract

  The evolution of Ca2-xNaxCuO2Cl2 from Mott insulator to superconductor was studied using angle-resolved photoemission spectroscopy. By measuring both the excitations near the Fermi energy as well as nonbonding states, we tracked the doping dependence of the electronic structure and the chemical potential with unprecedented precision. Our work reveals failures in the standard weakly interacting quasiparticle scenario, including the broad line shapes of the insulator and the apparently paradoxical shift of the chemical potential within the Mott gap. To resolve this, we develop a model where the quasiparticle is vanishingly small at half filling and grows upon doping, allowing us to unify properties such as the dispersion and Fermi wave vector with the chemical potential.

  View details for DOI 10.1103/PhysRevLett.93.267002

  View details for Web of Science ID 000226054600054

  View details for PubMedID 15698008

• Fermi surface reconstruction in the CDW state of CeTe3 observed by photoemission PHYSICAL REVIEW LETTERS Brouet, V., Yang, W. L., Zhou, X. J., Hussain, Z., Ru, N., Shin, K. Y., Fisher, I. R., Shen, Z. X. 2004; 93 (12)

  Abstract

  CeTe3 is a layered compound where an incommensurate charge density wave (CDW) opens a large gap ( approximately 400 meV) in optimally nested regions of the Fermi surface (FS), whereas other sections with poorer nesting remain ungapped. Through angle-resolved photoemission, we identify bands backfolded according to the CDW periodicity. They define FS pockets formed by the intersection of the original FS and its CDW replica. Such pockets illustrate very directly the role of nesting in the CDW formation but they could not be detected so far in a CDW system. We address the reasons for the weak intensity of the folded bands, by comparing different foldings coexisting in CeTe3.

  View details for DOI 10.1103/PhysRevLett.93.126405

  View details for Web of Science ID 000223923800059

  View details for PubMedID 15447291

• Angle-resolved photoemission study of the lightly doped cuprates Bi2212 International Symposium on Synchrotron Radiation Research for Spin and Electronic States in d and f Electron Systems Tanaka, K., Yoshida, T., Fujimori, A., Lu, D. H., Zhou, X. J., Shen, Z. X., Hussain, Z., Eisaki, H., Uchida, S., Sugaya, T., Mizuno, T., Terasaki, I. ELSEVIER SCIENCE BV. 2004: 277–79

  View details for DOI 10.1016/j.physb.2004.06.025

  View details for Web of Science ID 000224002800014

• ARPES study of T*-phase cuprate superconductor SmLa0.85Sr0.15CuO4-delta International Symposium on Synchrotron Radiation Research for Spin and Electronic States in d and f Electron Systems Ino, A., Higashiguchi, M., Yamazaki, K., Yamasaki, T., Narimura, T., Kobayashi, K., Shimada, K., Namatame, H., Taniguchi, M., Yoshida, T., Fujimori, A., Shen, Z. X., Kakeshita, T., Uchida, S., Adachi, S., Tajima, S. ELSEVIER SCIENCE BV. 2004: 274–76

  View details for DOI 10.1016/j.physb.2004.06.024

  View details for Web of Science ID 000224002800013

• Thermodynamic and transport properties of underdoped cuprates from ARPES data International Symposium on Synchrotron Radiation Research for Spin and Electronic States in d and f Electron Systems Yoshida, T., Zhou, X. J., Yagi, H., Lu, D. H., Tanaka, K., Fujimori, A., Hussain, Z., Shen, Z. X., Kakeshita, T., Eisaki, H., Uchida, S., Segawa, K., Lavrov, A. N., Ando, Y. ELSEVIER SCIENCE BV. 2004: 250–55

  View details for DOI 10.1016/j.physb.2004.06.017

  View details for Web of Science ID 000224002800006

• Coupling of the B-1g phonon to the antinodal electronic states of Bi2Sr2Ca0.92Y0.08Cu2O8+delta PHYSICAL REVIEW LETTERS Cuk, T., Baumberger, F., Lu, D. H., Ingle, N., Zhou, X. J., Eisaki, H., Kaneko, N., Hussain, Z., Devereaux, T. P., Nagaosa, N., Shen, Z. X. 2004; 93 (11)

  Abstract

  Angle-resolved photoemission spectroscopy on optimally doped Bi(2)Sr(2)Ca(0.92)Y(0.08)Cu(2)O(8+delta) uncovers a coupling of the electronic bands to a 40 meV mode in an extended k-space region away from the nodal direction, leading to a new interpretation of the strong renormalization of the electronic structure seen in Bi2212. Phenomenological agreements with neutron and Raman experiments suggest that this mode is the B(1g) oxygen bond-buckling phonon. A theoretical calculation based on this assignment reproduces the electronic renormalization seen in the data.

  View details for DOI 10.1103/PhysRevLett.93.117003

  View details for Web of Science ID 000223794400050

  View details for PubMedID 15447370

• Anisotropic electron-phonon interaction in the cuprates PHYSICAL REVIEW LETTERS Devereaux, T. P., Cuk, T., Shen, Z. X., Nagaosa, N. 2004; 93 (11)

  Abstract

  We explore manifestations of electron-phonon coupling on the electron spectral function for two phonon modes in the cuprates exhibiting strong renormalizations with temperature and doping. Applying simple symmetry considerations and kinematic constraints, we find that the out-of-plane, out-of-phase O buckling mode (B(1g)) involves small momentum transfers and couples strongly to electronic states near the antinode while the in-plane Cu-O breathing modes involve large momentum transfers and couples strongly to nodal electronic states. Band renormalization effects are found to be strongest in the superconducting state near the antinode, in full agreement with angle-resolved photoemission spectroscopy data.

  View details for DOI 10.1103/PhysRevLett.93.117004

  View details for Web of Science ID 000223794400051

  View details for PubMedID 15447371

• Effects of next-nearest-neighbor hopping t ' on the electronic structure of cuprate superconductors PHYSICAL REVIEW B Tanaka, K., Yoshida, T., Fujimori, A., Lu, D. H., Shen, Z. X., Zhou, X. J., Eisaki, H., Hussain, Z., Uchida, S., Aiura, Y., Ono, K., Sugaya, T., Mizuno, T., Terasaki, I. 2004; 70 (9)

  View details for DOI 10.1103/PhysRevB.70.092503

  View details for Web of Science ID 000224209200019

• A spectroscopic view of electron-phonon coupling at metal surfaces 5th Motorola Workshop on Computational Materials and Electronics Tang, S. J., Shi, J. R., Wu, B., Sprunger, P. T., Yang, W. L., Brouet, V., Zhou, X. J., Hussain, Z., Shen, Z. A., Zhang, Z. Y., Plummer, E. W. WILEY-V C H VERLAG GMBH. 2004: 2345–52

  View details for DOI 10.1002/pssb.200404890

  View details for Web of Science ID 000223394700021

• Dichotomy between nodal and antinodal quasiparticles in underdoped (La2-xSrx)CuO4 superconductors PHYSICAL REVIEW LETTERS Zhou, X. J., Yoshida, T., Lee, D. H., Yang, W. L., Brouet, V., Zhou, F., Ti, W. X., Xiong, J. W., Zhao, Z. X., Sasagawa, T., Kakeshita, T., Eisaki, H., Uchida, S., Fujimori, A., Hussain, Z., Shen, Z. X. 2004; 92 (18)

  Abstract

  High resolution angle-resolved photoemission measurements on an underdoped (La(2-x)Srx)CuO4 system show that, at energies below 70 meV, the quasiparticle peak is well defined around the (pi/2,pi/2) nodal region and disappears rather abruptly when the momentum is changed from the nodal point to the (pi,0) antinodal point along the underlying "Fermi surface." It indicates that there is an extra low energy scattering mechanism acting upon the antinodal quasiparticles. We propose that this mechanism is the scattering of quasiparticles across the nearly parallel segments of the Fermi surface near the antinodes.

  View details for DOI 10.1103/PhysRevLett.92.187001

  View details for Web of Science ID 000221277900054

  View details for PubMedID 15169524

• Direct extraction of the Eliashberg function for electron-phonon coupling: A case study of Be(10(1)over-bar0) PHYSICAL REVIEW LETTERS Shi, J. R., Tang, S. J., Wu, B., Sprunger, P. T., Yang, W. L., Brouet, V., Zhou, X. J., Hussain, Z., Shen, Z. X., Zhang, Z. Y., Plummer, E. W. 2004; 92 (18)

  Abstract

  We propose a systematic procedure to directly extract the Eliashberg function for electron-phonon coupling from high-resolution angle-resolved photoemission measurement. The procedure is successfully applied to the Be(10(-)10) surface, providing new insights into electron-phonon coupling at this surface. The method is shown to be robust against imperfections in experimental data and suitable for wider applications.

  View details for DOI 10.1103/PhysRevLett.92.186401

  View details for Web of Science ID 000221277900043

  View details for PubMedID 15169513

• Fully gapped single-particle excitations in lightly doped cuprates PHYSICAL REVIEW B Shen, K. M., Yoshida, T., Lu, D. H., Ronning, F., Armitage, N. P., Lee, W. S., Zhou, X. J., Damascelli, A., Feng, D. L., Ingle, N. J., Eisaki, H., Kohsaka, Y., Takagi, H., Kakeshita, T., Uchida, S., Mang, P. K., Greven, M., Onose, Y., Taguchi, Y., Tokura, Y., Komiya, S., Ando, Y., Azuma, M., Takano, M., Fujimori, A., Shen, Z. X. 2004; 69 (5)

  View details for DOI 10.1103/PhysRevB.69.054503

  View details for Web of Science ID 000220001700073

• Effect of chemical inhomogeneity in bismuth-based copper oxide superconductors PHYSICAL REVIEW B Eisaki, H., Kaneko, N., Feng, D. L., Damascelli, A., Mang, P. K., Shen, K. M., Shen, Z. X., Greven, M. 2004; 69 (6)

  View details for DOI 10.1103/PhysRevB.69.064512

  View details for Web of Science ID 000220092100073

• Sharp-mode coupling in high-Tc superconductors Nature Cuk, T., Shen, Z., Gromko, A., Sun, Z., Dessau, D. 2004; 432 (1)

  View details for DOI 10.1038/nature03163

• A Review of Electron-Phonon Coupling Seen in the High-Tc Superconductors by ARPES IPSS, basic solid state physics Cuk, T., Lu, D., Zhou, X., Shen, Z., Devereaux, T., Nagaosa, N. 2004

  View details for DOI 10.1002/pssb.200404959

• Angle-resolved photoemission spectral function analysis of the electron-doped cuprate Nd1.85Ce0.15CuO4 PHYSICAL REVIEW B Armitage, N. P., Lu, D. H., Kim, C., Damascelli, A., Shen, K. M., Ronning, F., Feng, D. L., Bogdanov, P., Zhou, X. J., Yang, W. L., Hussain, Z., Mang, P. K., Kaneko, N., Greven, M., Onose, Y., Taguchi, Y., Tokura, Y., Shen, Z. X. 2003; 68 (6)

  View details for DOI 10.1103/PhysRevB.68.064517

  View details for Web of Science ID 000185240600085

• Metallic behavior of lightly doped La2-xSrxCuO4 with a Fermi surface forming an arc PHYSICAL REVIEW LETTERS Yoshida, T., Zhou, X. J., Sasagawa, T., Yang, W. L., Bogdanov, P. V., Lanzara, A., Hussain, Z., Mizokawa, T., Fujimori, A., Eisaki, H., Shen, Z. X., Kakeshita, T., Uchida, S. 2003; 91 (2)

  Abstract

  Lightly doped La2-xSrxCuO4 in the so-called "insulating" spin-glass phase has been studied by angle-resolved photoemission spectroscopy. We have observed that a "quasiparticle" (QP) peak crosses the Fermi level in the node direction of the d-wave superconducting gap, forming an "arc" of Fermi surface, which explains the metallic behavior at high temperatures of the lightly doped materials. The QP spectral weight of the arc smoothly increases with hole doping, which we attribute to the n approximately x behavior of the carrier number in the underdoped and lightly doped regions.

  View details for DOI 10.1103/PhysRevLett.91.027001

  View details for Web of Science ID 000184086000038

  View details for PubMedID 12906502

• High-temperature superconductors: Universal nodal Fermi velocity. Nature Zhou, X. J., Yoshida, T., Lanzara, A., Bogdanov, P. V., Kellar, S. A., Shen, K. M., Yang, W. L., Ronning, F., Sasagawa, T., Kakeshita, T., Noda, T., Eisaki, H., Uchida, S., Lin, C. T., Zhou, F., Xiong, J. W., Ti, W. X., Zhao, Z. X., Fujimori, A., Hussain, Z., Shen, Z. 2003; 423 (6938): 398-?

  View details for PubMedID 12761537

• Universal nodal Fermi velocity NATURE Zhou, X. J., Yoshida, T., Lanzara, A., Bogdanov, P. V., Kellar, S. A., Shen, K. M., Yang, W. L., Ronning, F., Sasagawa, T., Kakeshita, T., Noda, T., Eisaki, H., Uchida, S., Lin, C. T., Zhou, F., Xiong, J. W., Ti, W. X., Zhao, Z. X., Fujimori, A., Hussain, Z., Shen, Z. X. 2003; 423 (6938): 398-398

  View details for DOI 10.1038/423398a

  View details for Web of Science ID 000183012000028

• ARPES study on electronic evolution in Ca2-xNaxCuO2Cl2 23rd International Conference on Low Temperature Physics (LT23) Sasagawa, T., Ronning, F., Kohsaka, Y., Shen, K. M., Yoshida, T., Azuma, M., Takano, M., Shen, Z. X., Takagi, H. ELSEVIER SCIENCE BV. 2003: 307–308

  View details for DOI 10.1016/S0921-4534(02)02462-0

  View details for Web of Science ID 000183340300147

• Angle-resolved photoemission spectroscopy of (Ca,Na)(2)CuO2Cl2 crystals: Fingerprints of a magnetic insulator in a heavily underdoped superconductor JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Kohsaka, Y., Sasagawa, T., Ronning, F., Yoshida, T., Kim, C., Hanaguri, T., Azuma, M., Takano, M., Shen, Z. X., Takagi, H. 2003; 72 (5): 1018-1021

  View details for DOI 10.1143/JPSJ.72.1018

  View details for Web of Science ID 000183823400013

• ARPES study of lightly doped La2-xSrxCuO4 23rd International Conference on Low Temperature Physics (LT23) Yoshida, T., Zhou, X. J., Sasagawa, T., Yang, W. L., Bogdanov, P. V., Lanzara, A., Hussain, Z., Mizokawa, T., Fujimori, A., Eisaki, H., Shen, Z. X., Kakeshita, T., Uchida, S. ELSEVIER SCIENCE BV. 2003: 303–304

  View details for DOI 10.1016/S0921-4534(02)02457-7

  View details for Web of Science ID 000183340300145

• Evolution of a metal to insulator transition in Ca2-xNaxCuO2Cl2 as seen by angle-resolved photoemission PHYSICAL REVIEW B Ronning, F., Sasagawa, T., Kohsaka, Y., Shen, K. M., Damascelli, A., Kim, C., Yoshida, T., Armitage, N. P., Lu, D. H., Feng, D. L., MILLER, L. L., Takagi, H., Shen, Z. X. 2003; 67 (16)

  View details for DOI 10.1103/PhysRevB.67.165101

  View details for Web of Science ID 000182824200021

• Band structure and Fermi surface of electron-doped C-60 monolayers SCIENCE Yang, W. L., Brouet, V., Zhou, X. J., Choi, H. J., Louie, S. G., Cohen, M. L., Kellar, S. A., Bogdanov, P. V., Lanzara, A., Goldoni, A., Parmigiani, F., Hussain, Z., Shen, Z. X. 2003; 300 (5617): 303-307

  Abstract

  C60 fullerides are challenging systems because both the electron-phonon and electron-electron interactions are large on the energy scale of the expected narrow band width. We report angle-resolved photoemission data on the band dispersion for an alkali-doped C60 monolayer and a detailed comparison with theory. Compared to the maximum bare theoretical band width of 170 meV, the observed 100-meV dispersion is within the range of renormalization by electron-phonon coupling. This dispersion is only a fraction of the integrated peak width, revealing the importance of many-body effects. Additionally, measurements on the Fermi surface indicate the robustness of the Luttinger theorem even for materials with strong interactions.

  View details for Web of Science ID 000182135400049

  View details for PubMedID 12690192

• Angle-resolved photoemission studies of the cuprate superconductors REVIEWS OF MODERN PHYSICS Damascelli, A., Hussain, Z., Shen, Z. X. 2003; 75 (2): 473-541

  View details for Web of Science ID 000182718200004

• Photoemission studies in MgB2 PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS Uchiyama, H., Tajima, S., Shen, K. M., Lu, D. H., Shen, Z. X. 2003; 385 (1-2): 85-90

  View details for Web of Science ID 000180663000011

• Universality of the electronic structure from a half-filled CuO2 plane PHYSICAL REVIEW B Ronning, F., Kim, C., Shen, K. M., Armitage, N. P., Damascelli, A., Lu, D. H., Feng, D. L., Shen, Z. X., MILLER, L. L., Kim, Y. J., Chou, F., Terasaki, I. 2003; 67 (3)

  View details for DOI 10.1103/PhysRevB.67.035113

  View details for Web of Science ID 000180943800041

• Angle-Resolved Photoemission Spectroscopy Studies of Cuprate Superconductors Frontiers of Science Shen, Z. 2003: 71-94

  View details for DOI 10.1142/9789812791207_0007

• Coupling of quasiparticles to phonons in high temperature superconductors JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Lanzara, A., Bogdanov, P. V., Zhou, X. J., Eisaki, H., Yoshida, T., Fujimori, A., Hussain, Z., Shen, Z. X. 2002; 127 (1-2): 37-41

  View details for Web of Science ID 000179903400005

• Anomalous momentum dependence of the quasiparticle scattering rate in overdoped Bi2Sr2CaCu2O8 PHYSICAL REVIEW LETTERS Bogdanov, P. V., Lanzara, A., Zhou, X. J., Yang, W. L., Eisaki, H., Hussain, Z., Shen, Z. X. 2002; 89 (16)

  Abstract

  The question of the anisotropy of the electron scattering in high temperature superconductors is investigated using high resolution angle-resolved photoemission data from Pb-doped Bi2Sr2CaCu2O8 (Bi2212) with suppressed superstructure. The scattering rate of low energy electrons along two bilayer-split pieces of the Fermi surface is measured (via the quasiparticle peak width), and no increase of scattering towards the antinode (pi,0) region is observed, contradicting the expectation from Q=(pi,pi) scattering. The results put a limit on the effects of Q=(pi,pi) scattering on the electronic structure of this overdoped superconductor with still very high T(c).

  View details for DOI 10.1103/PhysRevLett.89.167002

  View details for Web of Science ID 000178384300039

  View details for PubMedID 12398747

• High resolution angle-resolved photoemission study of high temperature superconductors: charge-ordering, bilayer splitting and electron-phonon coupling JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Zhou, X. J., Hussain, Z., Shen, Z. X. 2002; 126 (1-3): 145-162

  View details for Web of Science ID 000179709500012

• Role of the electron-phonon interaction in the strongly correlated cuprate superconductors PHILOSOPHICAL MAGAZINE B-PHYSICS OF CONDENSED MATTER STATISTICAL MECHANICS ELECTRONIC OPTICAL AND MAGNETIC PROPERTIES Shen, Z. X., Lanzara, A., Ishihara, S., Nagaosa, N. 2002; 82 (13): 1349-1368

  View details for DOI 10.1080/13642810210142735

  View details for Web of Science ID 000177901700001

• Evanescent microwave probe measurement of low-k dielectric films JOURNAL OF APPLIED PHYSICS Wang, Z. Y., Kelly, M. A., Shen, Z. X., Wang, G., Xiang, X. D., Wetzel, J. T. 2002; 92 (2): 808-811

  View details for DOI 10.1063/1.1481199

  View details for Web of Science ID 000176600000022

• Doping dependence of an n-type cuprate superconductor investigated by angle-resolved photoemission spectroscopy PHYSICAL REVIEW LETTERS Armitage, N. P., Ronning, F., Lu, D. H., Kim, C., Damascelli, A., Shen, K. M., Feng, D. L., Eisaki, H., Shen, Z. X., Mang, P. K., Kaneko, N., Greven, M., Onose, Y., Taguchi, Y., Tokura, Y. 2002; 88 (25)

  Abstract

  We present an angle-resolved photoemission doping dependence study of the n-type cuprate superconductor Nd(2-x)Ce(x)CuO(4+/-delta), from the half-filled Mott insulator to the T(c) = 24 K superconductor. In Nd2CuO4, we reveal the charge-transfer band for the first time. As electrons are doped into the system, this feature's intensity decreases with the concomitant formation of near- E(F) spectral weight. At low doping, the Fermi surface is an electron-pocket (with volume approximately x) centered at (pi,0). Further doping leads to the creation of a new holelike Fermi surface (volume approximately 1+x) centered at (pi,pi). These findings shed light on the Mott gap, its doping evolution, as well as the anomalous transport properties of the n-type cuprates.

  View details for DOI 10.1103/PhysRevLett.88.257001

  View details for Web of Science ID 000176554800043

  View details for PubMedID 12097118

• Electronic excitations near the Brillouin zone boundary of Bi2Sr2CaCu2O8+delta PHYSICAL REVIEW B Feng, D. L., Kim, C., Eisaki, H., Lu, D. H., Damascelli, A., Shen, K. M., Ronning, F., Armitage, N. P., Kaneko, N., Greven, M., Shimoyama, J., Kishio, K., Yoshizaki, R., Gu, G. D., Shen, Z. X. 2002; 65 (22)

  View details for DOI 10.1103/PhysRevB.65.220501

  View details for Web of Science ID 000176767100014

• Photoemission study of the intra-unit-cell coupling in a trilayer cuprate INTERNATIONAL JOURNAL OF MODERN PHYSICS B Feng, D. L., Eisaki, H., Shen, K. M., Damascelli, A., Kim, C., Lu, D. H., Shen, Z. X., Shimizu, K., Shimoyama, J. I., Kishio, K., Motoyama, N., Kaneko, N., Greven, M., Gu, G. D. 2002; 16 (11-12): 1691-1696

  View details for Web of Science ID 000176129800023

• Coexistence of interfering and noninterfering channels in resonant photoemission spectra across the Cu 2p -> 3d threshold PHYSICAL REVIEW B Pagliara, S., Sangaletti, L., Goldoni, A., Kim, C., Shen, Z. X., Revcolevschi, A., Dhalenne, G., Parmigiani, F. 2002; 65 (20)

  View details for DOI 10.1103/PhysRevB.65.205107

  View details for Web of Science ID 000176066600028

• Anomalous temperature dependence in the photoemission spectral function of cuprates PHYSICAL REVIEW B Kim, C., Ronning, F., Damascelli, A., Feng, D. L., Shen, Z. X., Wells, B. O., Kim, Y. J., Birgeneau, R. J., Kastner, M. A., MILLER, L. L., Eisaki, H., Uchida, S. 2002; 65 (17)

  View details for DOI 10.1103/PhysRevB.65.174516

  View details for Web of Science ID 000175619600115

• Momentum-resolved charge excitations in a prototype one-dimensional Mott insulator PHYSICAL REVIEW LETTERS Hasan, M. Z., Montano, P. A., Isaacs, E. D., Shen, Z. X., Eisaki, H., Sinha, S. K., Islam, Z., Motoyama, N., Uchida, S. 2002; 88 (17)

  Abstract

  We report momentum-resolved charge excitations in a one-dimensional (1D) Mott insulator studied using high resolution inelastic x-ray scattering over the entire Brillouin zone for the first time. Excitations at the insulating gap edge are found to be highly dispersive (momentum dependent) compared to excitations observed in two-dimensional Mott insulators. The observed dispersion in 1D cuprates ( SrCuO2 and Sr2CuO3) is consistent with charge excitations involving holons which is unique to spin-1/2 quantum chain systems. These results point to the potential utility of momentum-resolved inelastic x-ray scattering in providing valuable information about electronic structure of strongly correlated insulators.

  View details for DOI 10.1103/PhysRevLett.88.177403

  View details for Web of Science ID 000175054700052

  View details for PubMedID 12005784

• Electronic structure of MgB2 from angle-resolved photoemission spectroscopy PHYSICAL REVIEW LETTERS Uchiyama, H., Shen, K. M., Lee, S., Damascelli, A., Lu, D. H., Feng, D. L., Shen, Z. X., Tajima, S. 2002; 88 (15)

  Abstract

  The first angle-resolved photoemission spectroscopy results from MgB2 single crystals are reported. Along the GammaK and GammaM directions, we observed three distinct dispersive features approaching the Fermi energy. These can be assigned to the theoretically predicted sigma (B 2p(x,y)) and pi (B 2p(z)) bands. In addition, a small parabolic-like band is detected around the Gamma point, which can be attributed to a surface-derived state. The overall agreement between our results and the band calculations suggests that the electronic structure of MgB2 is of a conventional nature, thus implying that electron correlations are weak and may be of little importance to superconductivity in this system.

  View details for DOI 10.1103/PhysRevLett.88.157002

  View details for Web of Science ID 000174773400031

  View details for PubMedID 11955214

• Electronic structure of the trilayer cuprate superconductor Bi2Sr2Ca2Cu3O10+delta PHYSICAL REVIEW LETTERS Feng, D. L., Damascelli, A., Shen, K. M., Motoyama, N., Lu, D. H., Eisaki, H., Shimizu, K., Shimoyama, J., Kishio, K., Kaneko, N., Greven, M., Gu, G. D., Zhou, X. J., Kim, C., Ronning, F., Armitage, N. P., Shen, Z. X. 2002; 88 (10)

  Abstract

  The low-energy electronic structure of the nearly optimally doped trilayer cuprate superconductor Bi(2)Sr(2)Ca(2)Cu(3)O(10+delta) is investigated by angle-resolved photoemission spectroscopy. The normal state quasiparticle dispersion and Fermi surface and the superconducting d-wave gap and coherence peak are observed and compared with those of single- and bilayer systems. We find that both the superconducting gap magnitude and the relative coherence-peak intensity scale linearly with T(c) for various optimally doped materials.

  View details for DOI 10.1103/PhysRevLett.88.107001

  View details for Web of Science ID 000174342000052

  View details for PubMedID 11909381

• Doping-dependent evolution of the electronic structure of La2-xSrxCuO4 in the superconducting and metallic phases PHYSICAL REVIEW B Ino, A., Kim, C., Nakamura, M., Yoshida, T., Mizokawa, T., Fujimori, A., Shen, Z. X., Kakeshita, T., Eisaki, H., Uchida, S. 2002; 65 (9)

  View details for DOI 10.1103/PhysRevB.65.094504

  View details for Web of Science ID 000174547900104

• Electronic Band Structure of Layered Ruthenates Electron Spectroscopies Applied to Low-Dimensional Materials Puchkov, A., Shen, Z. Springer, Dordrecht. 2002: 445–496

  View details for DOI https://doi.org/10.1007/0-306-47126-4_9

• Angle-resolved photoemission study of Zn-doped PrBa 2 Cu 4 O 8 : Possible observation of single-particle spectral function for a Tomonaga-Luttinger liquid Phys. Rev. B Mizokawa, T., Nakada, K., Kim, C., Shen, Z., Yoshida, T., Fujimori, A., Horii, S., Yamada, Y., Ikuta, H., Mizutani, U. 2002; 65 (19): 193101

  View details for DOI 10.1103/PhysRevB.65.193101

• Comment on "Fermi surface, surface states, and surface reconstruction in Sr2RuO4" - Reply PHYSICAL REVIEW LETTERS Damascelli, A., Shen, K. M., Lu, D. H., Shen, Z. X. 2001; 87 (23)

  View details for DOI 10.1103/PhysRevLett.87.239702

  View details for Web of Science ID 000172545400050

• Surface electronic structure of Sr2RuO4 PHYSICAL REVIEW B Shen, K. M., Damascelli, A., Lu, D. H., Armitage, N. P., Ronning, F., Feng, D. L., Kim, C., Shen, Z. X., Singh, D. J., Mazin, I. I., Nakatsuji, S., Mao, Z. Q., Maeno, Y., Kimura, T., Tokura, Y. 2001; 64 (18)

  View details for Web of Science ID 000172239400016

• Photoemission study of Pb doped Bi2Sr2CaCu2O8: A Fermi surface picture PHYSICAL REVIEW B Bogdanov, P. V., Lanzara, A., Zhou, X. J., Kellar, S. A., Feng, D. L., Lu, E. D., Eisaki, H., Shimoyama, J. I., Kishio, K., Hussain, Z., Shen, Z. X. 2001; 64 (18)

  View details for Web of Science ID 000172239400019

• Charge excitations in a quantum antiferromagnet 3rd International Conference on New Theories, Discoveries and Applications of Superconductors and Related Materials Hasan, M. Z., Isaacs, E. D., Shen, Z. X., MILLER, L. L. ELSEVIER SCIENCE BV. 2001: 618–621

  View details for Web of Science ID 000172155700144

• Momentum resolved resonant inelastic X-ray scattering as a novel tool to study electronic structure of complex insulators 3rd International Conference on New Theories, Discoveries and Applications of Superconductors and Related Materials Hasan, M. Z., Isaacs, E. D., Shen, Z. X. ELSEVIER SCIENCE BV. 2001: 265–268

  View details for Web of Science ID 000172155700063

• Anomalous electronic structure and pseudogap effects in Nd1.85Ce0.15CuO4 PHYSICAL REVIEW LETTERS Armitage, N. P., Lu, D. H., Kim, C., Damascelli, A., Shen, K. M., Ronning, F., Feng, D. L., Bogdanov, P., Shen, Z. X., Onose, Y., Taguchi, Y., Tokura, Y., Mang, P. K., Kaneko, N., Greven, M. 2001; 87 (14)

  Abstract

  We report a high-resolution angle-resolved photoemission spectroscopic study of the electron-doped ( n-type) cuprate superconductor Nd1.85Ce0.15CuO4. We observe regions along the Fermi surface where the near- E(F) intensity is suppressed and the spectral features are broad in a manner reminiscent of the high-energy "pseudogap" in the underdoped p-type (hole doped) cuprates. However, instead of occurring near the (pi,0) region, as in the p-type materials, this pseudogap falls near the intersection of the underlying Fermi surface with the antiferromagnetic Brillouin zone boundary.

  View details for DOI 10.1103/PhysRevLett.87.147003

  View details for Web of Science ID 000171427500041

  View details for PubMedID 11580672

• X-ray standing-wave investigations of valence electronic structure PHYSICAL REVIEW B Woicik, J. C., Nelson, E. J., Heskett, D., Warner, J., Berman, L. E., Karlin, B. A., Vartanyants, I. A., Hasan, M. Z., Kendelewicz, T., Shen, Z. X., Pianetta, P. 2001; 64 (12)

  View details for Web of Science ID 000171244400038

• Evidence for ubiquitous strong electron-phonon coupling in high-temperature superconductors NATURE Lanzara, A., Bogdanov, P. V., Zhou, X. J., Kellar, S. A., Feng, D. L., Lu, E. D., Yoshida, T., Eisaki, H., Fujimori, A., Kishio, K., Shimoyama, J. I., Noda, T., Uchida, S., Hussain, Z., Shen, Z. X. 2001; 412 (6846): 510-514

  Abstract

  Coupling between electrons and phonons (lattice vibrations) drives the formation of the electron pairs responsible for conventional superconductivity. The lack of direct evidence for electron-phonon coupling in the electron dynamics of the high-transition-temperature superconductors has driven an intensive search for an alternative mechanism. A coupling of an electron with a phonon would result in an abrupt change of its velocity and scattering rate near the phonon energy. Here we use angle-resolved photoemission spectroscopy to probe electron dynamics-velocity and scattering rate-for three different families of copper oxide superconductors. We see in all of these materials an abrupt change of electron velocity at 50-80 meV, which we cannot explain by any known process other than to invoke coupling with the phonons associated with the movement of the oxygen atoms. This suggests that electron-phonon coupling strongly influences the electron dynamics in the high-temperature superconductors, and must therefore be included in any microscopic theory of superconductivity.

  View details for Web of Science ID 000170202900037

  View details for PubMedID 11484045

• Dual nature of the electronic structure of (La2-x-yNdySrx)CuO4 and La1.85Sr0.15CuO4 PHYSICAL REVIEW LETTERS Zhou, X. J., Yoshida, T., Kellar, S. A., Bogdanov, P. V., Lu, E. D., Lanzara, A., Nakamura, M., Noda, T., Kakeshita, T., Eisaki, H., Uchida, S., Fujimora, A., Hussain, Z., Shen, Z. X. 2001; 86 (24): 5578-5581

  Abstract

  High resolution angle-resolved photoemission measurements have been carried out on (La(1.4--x)-Nd(0.6)Sr(x))CuO(4), a model system with static one-dimensional (1D) charge ordering (stripe), and (La(1.85)-Sr(0.15))CuO(4), a high temperature superconductor (T(c) = 40 K) with possible dynamic stripes. In addition to the straight segments near ( pi,0) and ( 0,pi) antinodal regions, we have identified the existence of spectral weight along the [1,1] nodal direction in the electronic structure of both systems. This observation of nodal state, together with the straight segments near antinodal regions, reveals the dual nature of the electronic structure of stripes due to the competition of order and disorder.

  View details for Web of Science ID 000169239500043

  View details for PubMedID 11415305

• Bilayer splitting in the electronic structure of heavily overdoped Bi2Sr2CaCu2O8+delta PHYSICAL REVIEW LETTERS Feng, D. L., Armitage, N. P., Lu, D. H., Damascelli, A., Hu, J. P., Bogdanov, P., Lanzara, A., Ronning, F., Shen, K. M., Eisaki, H., Kim, C., Shen, Z. X., Shimoyama, J. I., Kishio, K. 2001; 86 (24): 5550-5553

  Abstract

  The electronic structure of heavily overdoped Bi(2)Sr(2)CaCu(2)O(8+delta) is investigated by angle-resolved photoemission spectroscopy. The long-sought bilayer band splitting in this two-plane system is observed in both normal and superconducting states, which qualitatively agrees with the bilayer Hubbard model calculations. The maximum bilayer energy splitting is about 88 meV for the normal state feature, while it is only about 20 meV for the superconducting peak.

  View details for Web of Science ID 000169239500036

  View details for PubMedID 11415298

• From Mott insulator to overdoped superconductor: evolution of the electronic structure of cuprates studied by ARPES JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Damascelli, A., Lu, D. H., Shen, Z. X. 2001; 117: 165-187

  View details for Web of Science ID 000169651700013

• Electronlike Fermi surface and remnant (pi,0) feature in overdoped La1.78Sr0.22CuO4 PHYSICAL REVIEW B Yoshida, T., Zhou, X. J., Nakamura, M., Kellar, S. A., Bogdanov, P. V., Lu, E. D., Lanzara, A., Hussain, Z., Ino, A., Mizokawa, T., Fujimori, A., Eisaki, H., Kim, C., Shen, Z. X., Kakeshita, T., Uchida, S. 2001; 63 (22)

  View details for Web of Science ID 000169283000008

• Superconducting gap and strong in-plane anisotropy in untwinned YBa2Cu3O7-delta PHYSICAL REVIEW LETTERS Lu, D. H., Feng, D. L., Armitage, N. P., Shen, K. M., Damascelli, A., Kim, C., Ronning, F., Shen, Z. X., Bonn, D. A., Liang, R., Hardy, W. N., Rykov, A. I., Tajima, S. 2001; 86 (19): 4370-4373

  Abstract

  With significantly improved sample quality and instrumental resolution, we clearly identify in the ( pi,0) photoemission spectra from YBa(2)Cu(3)O(6.993), in the superconducting state, the long-sought "peak-dip-hump" structure. This advance allows us to investigate the large a-b anisotropy of the in-plane electronic structure including, in particular, a 50% difference in the magnitude of the superconducting gap that scales with the energy position of the hump feature. This anisotropy, likely induced by the presence of the CuO chains, raises serious questions about attempts to quantitatively explain the YBa(2)Cu(3)O(7-delta) data from various experiments using models based on a perfectly square lattice.

  View details for Web of Science ID 000168591000045

  View details for PubMedID 11328177

• Evidence of electron fractionalization from photoemission spectra in the high temperature superconductors PHYSICAL REVIEW LETTERS Orgad, D., Kivelson, S. A., Carlson, E. W., Emery, V. J., Zhou, X. J., Shen, Z. X. 2001; 86 (19): 4362-4365

  Abstract

  In the normal state of the high temperature superconductors Bi(2)Sr(2)CaCu(2)O(8+delta) and La2(-x)Sr(x)CuO4, and in the related "stripe ordered" material, La(1.25)Nd(0.6)Sr(0.15)CuO4, there is sharp structure in the measured single hole spectral function, A<(k-->,omega), considered as a function of k--> at fixed small binding energy omega. At the same time, as a function of omega at fixed k--> on much of the putative Fermi surface, any structure in A<(k-->,omega), other than the Fermi cutoff, is very broad. This is characteristic of the situation in which there are no stable excitations with the quantum numbers of the electron, as is the case in the one-dimensional electron gas.

  View details for Web of Science ID 000168591000043

  View details for PubMedID 11328175

• A photoemission investigation of the superconducting gap in an electron-doped cuprate superconductor 8th International Conference on Electronic Spectroscopy and Structure Armitage, N. P., Lu, D. H., Kim, C., Damascelli, A., Shen, K. M., Ronning, F., Shen, Z. X., Onose, Y., Taguchi, Y., Tokura, Y. ELSEVIER SCIENCE BV. 2001: 623–627

  View details for Web of Science ID 000167832700096

• Inelastic X-ray scattering as a novel tool to study electronic excitations in complex insulators 8th International Conference on Electronic Spectroscopy and Structure Hasan, M. Z., Isaacs, E., Shen, Z. X., MILLER, L. L. ELSEVIER SCIENCE BV. 2001: 705–709

  View details for Web of Science ID 000167832700109

• Fermi surface of Sr2RuO4 from angle resolved photoemission 8th International Conference on Electronic Spectroscopy and Structure Damascelli, A., Shen, K. M., Lu, D. H., Armitage, N. P., Ronning, F., Feng, D. L., Kim, C., Shen, Z. X., Kimura, T., Tokura, Y., Mao, Z. Q., Maeno, Y. ELSEVIER SCIENCE BV. 2001: 641–646

  View details for Web of Science ID 000167832700099

• Superconducting gap anisotropy in Nd1.85Ce0.15CuO4: Results from photoemission PHYSICAL REVIEW LETTERS Armitage, N. P., Lu, D. H., Feng, D. L., Kim, C., Damascelli, A., Shen, K. M., Ronning, F., Shen, Z. X., Onose, Y., Taguchi, Y., Tokura, Y. 2001; 86 (6): 1126-1129

  Abstract

  We have performed angle resolved photoelectron spectroscopy on the electron doped cuprate superconductor Nd1.85Ce0.15CuO4. A comparison of the leading edge midpoints between the superconducting and normal states reveals a small, but finite shift of 1.5-2 meV near the ( pi,0) position, but no observable shift along the zone diagonal near ( pi/2, pi/2). This is interpreted as evidence for an anisotropic superconducting gap in the electron doped materials, which is consistent with the presence of d-wave superconducting order in this cuprate superconductor.

  View details for Web of Science ID 000166781000046

  View details for PubMedID 11178026

• Pseudogaps and dynamical stripes in La2-xSrxCuO4 from photoemission spectroscopy CREST International Workshop on Pseudo Gap, Spin Gap and Anomalous Metals Fujimori, A., Ino, A., Yoshida, T., Mizokawa, T., Nakamura, M., Kim, C., Shen, Z. X., Kishio, K., Kakeshita, T., Eisaki, H., Uchida, S. PERGAMON-ELSEVIER SCIENCE LTD. 2001: 15–19

  View details for Web of Science ID 000166040100004

• Angle resolved photoemission spectroscopy of Sr2CuO2Cl2 - a revisit American Physical Society Dürr, C., Legner, S., Hayn, R., Borisenko, S., Hu, Z., Theresiak, A., Knupfer, M., Golden, M., Fink, J., Ronning, F., Shen, Z., Eisaki, H., Uchida, S., Janowitz, C., Müller, R., Johnson, R., Rossnagel, K., Kipp, L., Reichardt, G. 2001; 63 (1): 014505

  View details for DOI 10.1103/PhysRevB.63.014505

• Photoemission study of Pb doped Bi 2 Sr 2 CaCu 2 O 8 : A Fermi surface picture Photoemission study of Pb doped Bi 2 Sr 2 CaCu 2 O 8 : A Fermi surface picture Bogdanov, P., Lanzara, A., Zhou, X., Kellar, S., Feng, D., Lu, E., Eisaki, H., Shimoyama, J., Kishio, K., Hussain, Z., Shen, Z. 2001; 64 (18)

  View details for DOI 10.1103/PhysRevB.64.180505

• Chapter 201 Angle-resolved photoemission studies of untwinned yttrium barium copper oxide Handbook on the Physics and Chemistry of Rare Earths Schabel, M., Shen, Z. Elsevier. 2001: 391–435

  View details for DOI 10.1016/S0168-1273(01)31010-3

• Evidence for abrupt change in dispersion and scattering rate of quasiparticles in Bi2Sr2CaCu2O8 CREST International Workshop on Pseudo Gap, Spin Gap and Anomalous Metals Lanzara, A., Bogdanov, P. V., Kellar, S. A., Zhou, X. J., Lu, E. D., Gu, G., Shimoyama, J. I., Kishio, K., Hussain, Z., Shen, Z. X. PERGAMON-ELSEVIER SCIENCE LTD. 2001: 21–24

  View details for Web of Science ID 000166040100005

• Nodal spectral weight and Fermi surface in La2-xSrxCuO4 3rd International Conference on Stripes and High Tc Superconductivity (STRIPES 2000) Yoshida, T., Nakamura, M., Ino, A., Mizokawa, T., Fujimori, A., Zhou, X. J., Kellar, S. A., Bogdanov, P. V., Lu, E. D., Lanzara, A., Eisaki, H., Hussain, Z., Shen, Z. X., Kakeshita, T., Uchida, S. WORLD SCIENTIFIC PUBL CO PTE LTD. 2000: 3777–82

  View details for Web of Science ID 000166507300075

• ARPES study of LSCO and PBCO: Electronic structure of the stripe phase and the 1/4-filled Cu-O chains 3rd International Conference on Stripes and High Tc Superconductivity (STRIPES 2000) Mizokawa, T., Ino, A., Yoshida, T., Fujimori, A., Kim, C., Eisaki, H., Shen, Z. X., Horii, S., Kakeshita, T., Uchida, S., Tomimoto, K., Tajima, S., Yamada, Y. WORLD SCIENTIFIC PUBL CO PTE LTD. 2000: 3602–9

  View details for Web of Science ID 000166507300049

• Fermi surface, surface states, and surface reconstruction in Sr2RuO4 PHYSICAL REVIEW LETTERS Damascelli, A., Lu, D. H., Shen, K. M., Armitage, N. P., Ronning, F., Feng, D. L., Kim, C., Shen, Z. X., Kimura, T., Tokura, Y., Mao, Z. Q., Maeno, Y. 2000; 85 (24): 5194-5197

  View details for Web of Science ID 000165800000045

• Angle-resolved photoemission study of insulating and metallic Cu-O chains in PrBa2Cu3O7 and PrBa2Cu4O8 PHYSICAL REVIEW LETTERS Mizokawa, T., Kim, C., Shen, Z. X., Ino, A., Yoshida, T., Fujimori, A., Goto, M., Eisaki, H., Uchida, S., Tagami, M., Yoshida, K., Rykov, A. I., Siohara, Y., Tomimoto, K., Tajima, S., Yamada, Y., Horii, S., Yamada, N., Yamada, Y., Hirabayashi, I. 2000; 85 (22): 4779-4782

  View details for Web of Science ID 000165556600034

• On the similarity of the spectral weight pattern of Bi2Sr2CaCuO8+delta and La1.48Nd0.4Sr0.12CuO4 International Conference on Materials and Mechanisms of Superconductivity High Temperature Superconductors VI Feng, D. L., Lu, D. H., Shen, K. M., Oh, S., Andrus, A., O'Donnell, J., Eckstein, J. N., Shimoyama, J., Kishio, K., Shen, Z. X. ELSEVIER SCIENCE BV. 2000: 2097–2098

  View details for Web of Science ID 000165856000010

• Particle-hole excitations in insulating antiferromagnet Ca2CuO2Cl2 International Conference on Materials and Mechanisms of Superconductivity High Temperature Superconductors VI Hasan, M. Z., Isaacs, E. D., Shen, Z. X., MILLER, L. L. ELSEVIER SCIENCE BV. 2000: 781–782

  View details for Web of Science ID 000165855700037

• Fermi surface, pseudogap and superconducting gap in La2-xSrxCuO4 International Conference on Materials and Mechanisms of Superconductivity High Temperature Superconductors VI Fujimori, A., Ino, A., Yoshida, T., Mizokawa, T., Nakamura, M., Kim, C., Shen, Z. X., Kakeshita, T., Eisaki, H., Uchida, S. ELSEVIER SCIENCE BV. 2000: 2067–2070

  View details for Web of Science ID 000165856000002

• Electronic structure of Nd1.85Ce0.15CuO4: Evidence for a disparity between hole and electron doped cuprate superconductors International Conference on Materials and Mechanisms of Superconductivity High Temperature Superconductors VI Armitage, N. P., Lu, D. H., Kim, C., Damascelli, A., Shen, K. M., Ronning, F., Onose, Y., Taguchi, Y., Tokura, Y., Shen, Z. X. ELSEVIER SCIENCE BV. 2000: 2083–2086

  View details for Web of Science ID 000165856000006

• ARPES features of the AF insulators Sr2CuO2Cl2 and Ca2CuO2Cl2 close to the AF zone boundary International Conference on Materials and Mechanisms of Superconductivity High Temperature Superconductors VI Ronning, F., Kim, C., Damascelli, A., Armitage, N. P., Lu, D. H., Shen, K. M., MILLER, L. L., Kim, Y. J., Kastner, M. A., Birgeneau, R. J., Shen, Z. X. ELSEVIER SCIENCE BV. 2000: 2087–2090

  View details for Web of Science ID 000165856000007

• Evidence for an energy scale for quasiparticle dispersion in Bi2Sr2CaCu2O8 Physical review letters Bogdanov, P. V., Lanzara, A., Kellar, S. A., Zhou, X. J., Lu, E. D., Zheng, W. J., Gu, G., Shimoyama, J., Kishio, K., Ikeda, H., Yoshizaki, R., Hussain, Z., Shen, Z. X. 2000; 85 (12): 2581-4

  Abstract

  Quasiparticle dispersion in Bi2Sr2CaCu2O8 is investigated with improved angular resolution as a function of temperature and doping. Unlike the linear dispersion predicted by the band calculation, the data show a sharp break in dispersion at 50+/-15 meV binding energy where the velocity changes by a factor of 2 or more. This change provides an energy scale in the quasiparticle self-energy. This break in dispersion is evident at and away from the d-wave node line, but the magnitude of the dispersion change decreases with temperature and with increasing doping.

  View details for PubMedID 10978112

• Electronic structure of La2-xSrxCuO4 in the vicinity of the superconductor-insulator transition PHYSICAL REVIEW B Ino, A., Kim, C., Nakamura, M., Yoshida, T., Mizokawa, T., Shen, Z. X., Fujimori, A., Kakeshita, T., Eisaki, H., Uchida, S. 2000; 62 (6): 4137-4141

  View details for Web of Science ID 000088727900078

• Signature of superfluid density in the single-particle excitation spectrum of Bi(2)Sr(2)CaCu(2)O(8+delta) Science (New York, N.Y.) Feng, D. L., Lu, D. H., Shen, K. M., Kim, C., Eisaki, H., Damascelli, A., Yoshizaki, R., Shimoyama, J., Kishio, K., Gu, G. D., Oh, S., Andrus, A., O'Donnell, J., Eckstein, J. N., Shen, Z. 2000; 289 (5477): 277-81

  Abstract

  We report that the doping and temperature dependence of photoemission spectra near the Brillouin zone boundary of Bi(2)Sr(2)CaCu(2)O(8+delta)exhibit unexpected sensitivity to the superfluid density. In the superconducting state, the photoemission peak intensity as a function of doping scales with the superfluid density and the condensation energy. As a function of temperature, the peak intensity shows an abrupt behavior near the superconducting phase transition temperature where phase coherence sets in, rather than near the temperature where the gap opens. This anomalous manifestation of collective effects in single-particle spectroscopy raises important questions concerning the mechanism of high-temperature superconductivity.

  View details for PubMedID 10894771

• Signature of superfluid density in the single-particle excitation spectrum of Bi2Sr2CaCu2O8+delta SCIENCE Feng, D. L., Lu, D. H., Shen, K. M., Kim, C., Eisaki, H., Damascelli, A., Yoshizaki, R., Shimoyama, J., Kishio, K., Gu, G. D., Oh, S., Andrus, A., O'Donnell, J., Eckstein, J. N., Shen, Z. X. 2000; 289 (5477): 277-281

  Abstract

  We report that the doping and temperature dependence of photoemission spectra near the Brillouin zone boundary of Bi(2)Sr(2)CaCu(2)O(8+delta)exhibit unexpected sensitivity to the superfluid density. In the superconducting state, the photoemission peak intensity as a function of doping scales with the superfluid density and the condensation energy. As a function of temperature, the peak intensity shows an abrupt behavior near the superconducting phase transition temperature where phase coherence sets in, rather than near the temperature where the gap opens. This anomalous manifestation of collective effects in single-particle spectroscopy raises important questions concerning the mechanism of high-temperature superconductivity.

  View details for Web of Science ID 000088169400035

• Electronic structure of mott insulators studied by inelastic X-ray scattering Science (New York, N.Y.) Hasan, M. Z., Isaacs, E. D., Shen, Z., Miller, L. L., Tsutsui, K., Tohyama, T., Maekawa, S. 2000; 288 (5472): 1811-4

  Abstract

  The electronic structure of Mott insulators continues to be a major unsolved problem in physics despite more than 50 years of research. Well-developed momentum-resolved spectroscopies such as photoemission or neutron scattering cannot probe the full Mott gap. High-resolution resonant inelastic x-ray scattering revealed dispersive charge excitations across the Mott gap in a high-critical temperature parent cuprate (Ca(2)CuO(2)Cl(2)), shedding light on the anisotropy of the Mott gap. These charge excitations across the Mott gap can be described within the framework of the Hubbard model.

  View details for PubMedID 10846160

• Electronic structure of Mott insulators studied by inelastic X-ray scattering SCIENCE Hasan, M. Z., Isaacs, E. D., Shen, Z. X., MILLER, L. L., Tsutsui, K., Tohyama, T., Maekawa, S. 2000; 288 (5472): 1811-1814

  Abstract

  The electronic structure of Mott insulators continues to be a major unsolved problem in physics despite more than 50 years of research. Well-developed momentum-resolved spectroscopies such as photoemission or neutron scattering cannot probe the full Mott gap. High-resolution resonant inelastic x-ray scattering revealed dispersive charge excitations across the Mott gap in a high-critical temperature parent cuprate (Ca(2)CuO(2)Cl(2)), shedding light on the anisotropy of the Mott gap. These charge excitations across the Mott gap can be described within the framework of the Hubbard model.

  View details for Web of Science ID 000087503800046

• Final Report to the DOE on the Construction of the High Energy Resolution Spectrometer (HERS) Endstation on Beamline 10.0.1.1 of the Advanced Light Source Kellar, S., Shen, Z. Stanford University. 2000
• Cover-Superconducting secrets-(ARPES data for Nd1. 85Ce0. 15CuO4, an electron-doped cuprate superconductor Physics World Armitage, N., Shen, Z., Tokura, Y. 2000; 13 (2): 33
• Metallic character in the electronic structure of the stripe phase Physical Review Letters Zhou, ., Yoshida, T., Kellar, S., Bogdanov, P., Lu, E., Lanzara, A., Nakamura, M., Noda, T., Kakeshita, T., Eisaki, H., Uchida, S., Fujimori, A., Hussain, Z., Shen, Z. 2000; 86
• Temperature Dependence of electronic Properties of K3C60 and K4C60 Single Phase Films Investigated by Means of Electron Spectroscopies JOURNAL OF CHEMICAL PHYSICS Goldoni, A., Sangaletti, L., Friedmann, S., Shen, Z., Peloi, M., Parmigiani, F., Comelli, G., Paolucci, G. 2000; 113 (18): 8266-8275
• Spin liquid state around a doped hole in insulating cuprates JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Tohyama, T., Shibata, Y., Maekawa, S., Shen, Z. X., Nagaosa, N., Miller, L. L. 2000; 69 (1): 9–12

  View details for DOI 10.1143/JPSJ.69.9

  View details for Web of Science ID 000085999500003

• Direct Electronic Structure Measurements of the Colossal Magnetoresistive Oxides Colossal Magnetoresistive Oxides Dessau, D., Shen, Z. Gordon and Breach Publishers. 2000
• Angle-resolved photoemission study of untwinned PrBa2Cu3O7: Undoped CuO2 plane and doped CuO3 chain PHYSICAL REVIEW B Mizokawa, T., Kim, C., Shen, Z. X., Ino, A., Fujimori, A., Goto, M., Eisaki, H., Uchida, S., Tagami, M., Yoshida, K., Rykov, A. I., Siohara, Y., Tomimoto, K., Tajima, S. 1999; 60 (17): 12335-12341

  View details for Web of Science ID 000083808700078

• One-Dimensional Electronic Structure and Suppression of d-Wave Node State in (La(1.28)Nd(0.6)Sr(0.12))CuO(4). Science (New York, N.Y.) Zhou, X. J., Bogdanov, P., Kellar, S. A., Noda, T., Eisaki, H., Uchida, S., Hussain, Z., Shen, Z. 1999; 286 (5438): 268-272

  Abstract

  Angle-resolved photoemission spectroscopy was carried out on (La(1.28)Nd(0.6) Sr(0.12))CuO(4), a model system of the charge- and spin-ordered state, or stripe phase. The electronic structure contains characteristic features consistent with other cuprates, such as the flat band at low energy near the Brillouin zone face. However, the low-energy excitation near the expected d-wave node region is strongly suppressed. The frequency-integrated spectral weight is confined inside one-dimensional segments in the momentum space (defined by horizontal momenta &cjs3539;k(x)&cjs3539; = pi/4 and vertical momenta &cjs3539;k(y)&cjs3539; = pi/4), deviating strongly from the more rounded Fermi surface expected from band calculations. This departure from the two-dimensional Fermi surface persists to a very high energy scale. These results provide important information for establishing a theory to understand the charge and spin ordering in cuprates and their relation with high-temperature superconductivity.

  View details for PubMedID 10514366

• Novel electronic structure of cuprate superconductors revealed by the anomalous spectral lineshape in ARPES experiments Shen, Z. X., Sawatzky, G. A. WILEY-V C H VERLAG GMBH. 1999: 523–29

  View details for DOI 10.1002/(SICI)1521-3951(199909)215:1<523::AID-PSSB523>3.0.CO;2-S

  View details for Web of Science ID 000082487800086

• Angle-resolved photoemission electron spectroscopy reveals a Fermi surface remnant with a d-wave like dispersion in the Mott insulator, Ca2CuO2Cl2 7th NEC Symposium on Fundamental Approaches to New Material Phases - Phase Control in Spin-Charge-Orbital Complex Systems Ronning, F., Kim, C., Shen, Z. X. ELSEVIER SCIENCE SA. 1999: 17–21

  View details for Web of Science ID 000081887800005

• Phase transition, molecular motions, and inequivalent carbon atoms in K3C60 (111) single-phase ordered films PHYSICAL REVIEW B Goldoni, A., Sangaletti, L., Parmagiani, F., Friedmann, S. L., Shen, Z. X., Peloi, M., Comelli, G., Paolucci, G. 1999; 59 (24): 16071–75

  View details for DOI 10.1103/PhysRevB.59.16071

  View details for Web of Science ID 000081134700064

• Condensed matter physics - Is this why T-c is so low? SCIENCE Balatsky, A. V., Shen, Z. X. 1999; 284 (5417): 1137-1138

  View details for Web of Science ID 000080359100026

• Fermi surface evolution in cuprates: an angle-resolved photoemission study 1st Euroconference on Anomalous Complex Superconductors Ronning, F., Kim, C., Shen, Z. X. ELSEVIER SCIENCE BV. 1999: 320–324

  View details for Web of Science ID 000081173100036

• Fermi surface and band dispersion in La2-xSrxCuO4 JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Ino, A., Kim, C., Mizokawa, T., Shen, Z. X., Fujimori, A., Takaba, M., Tamasaku, K., Eisaki, H., Uchida, S. 1999; 68 (5): 1496–99

  View details for DOI 10.1143/JPSJ.68.1496

  View details for Web of Science ID 000080552800009

• Electronic structure measurements of colossal magnetoresistive manganese-oxides: Polaronic effects on the band structure International Conference on Superconductivity and Magnetism Dessau, D. S., Saitoh, T., Park, C. H., Shen, Z. X., Villella, P., Hamada, N., Moritomo, Y., Tokura, Y. SPRINGER/PLENUM PUBLISHERS. 1999: 273–76

  View details for Web of Science ID 000079294300063

• Fermi-Liquid Versus Pseudogap Behaviors in Filling-Control Transition-Metal Oxides Physics and Chemistry of Transition Metal Oxides Fujimori, A., Yoshida, T., Ino, A., Mizokawa, T., Kim, C., Shen, Z., Taguchi, Y., Katsufuji, T., Tokura, Y., Eisaki, H., Uchida, S., Kishio, K. Springer, Berlin, Heidelberg. 1999: 111–119
• Dominant role of a pseudogap in the physics of the colossal magnetoresistive oxides 1st International Conference on New Theories, Discoveries, and Applications of Superconductors and Related Materials (New3SC-1) Dessau, D. S., Saitoh, T., Park, C. H., Shen, Z. X., Moritomo, Y., Tokura, Y. WORLD SCIENTIFIC PUBL CO PTE LTD. 1998: 3389–92

  View details for Web of Science ID 000079114500101

• Photoemission evidence for a remnant fermi surface and a d-wave-like dispersion in insulating Ca2CuO2Cl2 Science (New York, N.Y.) Ronning, F., Kim, C., Feng, D. L., Marshall, D. S., Loeser, A. G., Miller, L. L., Eckstein, J. N., Bozovic, I., Shen, Z. 1998; 282 (5396): 2067-72

  Abstract

  An angle-resolved photoemission study is reported on Ca2CuO2Cl2, a parent compound of high-Tc superconductors. Analysis of the electron occupation probability, n(k), from the spectra shows a steep drop in spectral intensity across a contour that is close to the Fermi surface predicted by the band calculation. This analysis reveals a Fermi surface remnant, even though Ca2CuO2Cl2 is a Mott insulator. The lowest energy peak exhibits a dispersion with approximately the &cjs3539;coskxa - coskya&cjs3539; form along this remnant Fermi surface. Together with the data from Dy-doped Bi2Sr2CaCu2O8+delta, these results suggest that this d-wave-like dispersion of the insulator is the underlying reason for the pseudo gap in the underdoped regime.

  View details for PubMedID 9851925

• ARPES results on Sr2RuO4: Fermi surface revisited PHYSICAL REVIEW B Puchkov, A. V., Shen, Z. X., Kimura, T., Tokura, Y. 1998; 58 (20): 13322-13325

  View details for Web of Science ID 000077279800004

• Correlation and electron-phonon effects in the valence-band photoemission spectra of single-phase K3C60 films PHYSICAL REVIEW B Goldoni, A., Friedmann, S. L., Shen, Z. X., Parmigiani, F. 1998; 58 (16): 11023-11028

  View details for Web of Science ID 000076716500133

• Chemical potential shift, density of states and Fermi surfaces in overdoped and underdoped La2-xSrxCuO4 International Conference on Spectroscopies in Novel Superconductors (SNS'97) Fujimori, A., Ino, A., Mizokawa, T., Kim, C., Shen, Z. X., Sasagawa, T., Kimura, T., Kishio, K., Takaba, M., Tamasaku, K., Eisaki, H., Uchidau, S. PERGAMON-ELSEVIER SCIENCE LTD. 1998: 1892–96

  View details for Web of Science ID 000077460500055

• (Sr1-xCax)(3)Ru2O7 system: Optical and ARPES results Puchkov, A. V., Schabel, M. C., Basov, D. N., Startseva, T., Cao, G., Timusk, T., Shen, Z. X. PERGAMON-ELSEVIER SCIENCE LTD. 1998: 1907–11

  View details for DOI 10.1016/S0022-3697(98)00146-2

  View details for Web of Science ID 000077460500058

• Comparison of the measured electronic structure of the colossal magnetoresistive manganites and high T-c superconductors: Band structure, photoemission lineshapes, and a pseudogap International Conference on Spectroscopies in Novel Superconductors (SNS'97) Dessau, D. S., Saitoh, T., Villella, P., Park, C. H., Shen, Z. X., Moritomo, Y., Tokura, Y. PERGAMON-ELSEVIER SCIENCE LTD. 1998: 1917–20

  View details for Web of Science ID 000077460500060

• Layered ruthenium oxides: From band metal to Mott insulator PHYSICAL REVIEW LETTERS Puchkov, A. V., Schabel, M. C., Basov, D. N., Startseva, T., Cao, G., Timusk, T., Shen, Z. X. 1998; 81 (13): 2747–50

  View details for DOI 10.1103/PhysRevLett.81.2747

  View details for Web of Science ID 000076133300032

• Electronic band structure of Sr3Ru2O7 PHYSICAL REVIEW B Puchkov, A. V., Shen, Z. X., Cao, G. 1998; 58 (11): 6671–75

  View details for DOI 10.1103/PhysRevB.58.6671

  View details for Web of Science ID 000076058800001

• Systematics of the photoemission spectral function of cuprates: Insulators and hole- and electron-doped superconductors PHYSICAL REVIEW LETTERS Kim, C., White, P. J., Shen, Z. X., Tohyama, T., Shibata, Y., Maekawa, S., Wells, B. O., Kim, Y. J., Birgeneau, R. J., Kastner, M. A. 1998; 80 (19): 4245-4248

  View details for Web of Science ID 000073550200034

• Temperature-induced momentum-dependent spectral weight transfer in Bi2Sr2CaCu2O8+delta Science (New York, N.Y.) Shen, Z., White, P. J., Feng, D. L., Kim, C., Gu, G. D., Ikeda, H., Yoshizaki, R., Koshizuka, N. 1998; 280 (5361): 259-62

  Abstract

  Angle-resolved photoemission data from the cuprate superconductor Bi2Sr2CaCu2O8+delta above and below the superconducting transition temperature Tc reveal momentum-dependent changes that extend up to an energy of about 0.3 electron volt, or 40kTc (where k is the Boltzmann constant). The data suggest an anomalous transfer of spectral weight from one momentum to another, involving a sizable momentum transfer Q approximately (0.45pi, 0). The observed Q is intriguingly near the charge-order periodicity required if fluctuating charge stripes are present.

  View details for PubMedID 9535649

• Angle-resolved photoemission on untwinned YBa2Cu3O6.95. I. Electronic structure and dispersion relations of surface and bulk bands PHYSICAL REVIEW B Schabel, M. C., Park, C. H., Matsuura, A., Shen, Z. X., Bonn, D. A., Liang, R. X., Hardy, W. N. 1998; 57 (10): 6090–6106

  View details for DOI 10.1103/PhysRevB.57.6090

  View details for Web of Science ID 000072486500075

• Angle-resolved photoemission on untwinned YBa2Cu3O6.95. II. Determination of Fermi surfaces PHYSICAL REVIEW B Schabel, M. C., Park, C. H., Matsuura, A., Shen, Z. X., Bonn, D. A., Liang, R. X., Hardy, W. N. 1998; 57 (10): 6107–15

  View details for DOI 10.1103/PhysRevB.57.6107

  View details for Web of Science ID 000072486500076

• Low energy k-dependent electronic structure of the layered magnetoresistive oxide La1.2Sr1.8Mn2O7 Symposium on Metallic Magnetic Oxides at the Materials-Research-Society Fall Meeting Saitoh, T., Dessau, D. S., Park, C. H., Shen, Z. X., Villella, P., Hamada, N., Moritomo, Y., Tokura, Y. MATERIALS RESEARCH SOCIETY. 1998: 213–218

  View details for Web of Science ID 000073253400030

• Angle-Resolved Photoemission Study of High-Tc Superconductors: Insulators, Metals and Superconductors Models and Phenomenology fro Conventional and High-temperature Superconductivity Shen, Z. IOS Press/Ohmsha. 1998: 141
• Metal-insulator transition in NiS 2 − x Se x and the local impurity self-consistent approximation model Physical Review B Matsuura, A., Watanabe, H., Kim, C., Doniach, S., Shen, Z., Thio, T., Bennett, J. 1998; 58 (7): 3690
• k -Dependent Electronic Structure, a Large “Ghost” Fermi Surface, and a Pseudogap in a Layered Magnetoresistive Oxide Physical Review Letters Dessau, D., Saitoh, T., Park, C., Shen, Z., Villella, P., Hamada, N., Moritomo, Y., Tokura, Y. 1998; 81 (1)
• Experimental determination of the key energy scales in the colossal magnetoresistive manganites Symposium on Metallic Magnetic Oxides at the Materials-Research-Society Fall Meeting Dessau, D. S., Saitoh, T., Park, C. H., Shen, Z. X., Moritomo, Y., Tokura, Y. MATERIALS RESEARCH SOCIETY. 1998: 181–186

  View details for Web of Science ID 000073253400027

• Separation of spin and charge excitations in one-dimensional SrCuO2 PHYSICAL REVIEW B Kim, C., Shen, Z. X., Motoyama, N., Eisaki, H., Uchida, S., Tohyama, T., Maekawa, S. 1997; 56 (24): 15589-15595

  View details for Web of Science ID 000071251000020

• Temperature and doping dependence of the Bi-Sr-Ca-Cu-O electronic structure and fluctuation effects PHYSICAL REVIEW B Loeser, A. G., Shen, Z. X., Schabel, M. C., Kim, C., Zhang, M., Kapitulnik, A., Fournier, P. 1997; 56 (21): 14185–89

  View details for DOI 10.1103/PhysRevB.56.14185

  View details for Web of Science ID A1997YJ87900097

• Recent photoemission data from underdoped Bi2212 single crystals Shen, Z. X. ELSEVIER SCIENCE BV. 1997: 123–123

  View details for Web of Science ID A1997XZ90400035

• Measurement of an anisotropic energy gap in single plane Bi2Sr2-xLaxCuO6+delta PHYSICAL REVIEW LETTERS Harris, J. M., White, P. J., Shen, Z. X., Ikeda, H., Yoshizaki, R., Eisaki, H., Uchida, S., Si, W. D., Xiong, J. W., Zhao, Z. X., Dessau, D. S. 1997; 79 (1): 143-146

  View details for Web of Science ID A1997XH87000036

• Electronic states and effective Hamiltonian of CuGeO3 5th International Conference / 45th Yamada Conference on Physics of Transition Metals (ICPTM 96) Tohyama, T., Mizuno, Y., Maekawa, S., Kim, C., Shen, Z. X. ELSEVIER SCIENCE BV. 1997: 135–136

  View details for Web of Science ID A1997XM23300049

• Site-specific unoccupied electronic structure of one-dimensional SrCuO2 PHYSICAL REVIEW B Knupfer, M., Neudert, R., Kielwein, M., Haffner, S., Golden, M. S., Fink, J., Kim, C., Shen, Z. X., Merz, M., Nucker, N., Schuppler, S., Motoyama, N., Eisaki, H., Uchida, S., Hu, Z., Domke, M., Kaindl, G. 1997; 55 (12): R7291–R7294

  View details for DOI 10.1103/PhysRevB.55.R7291

  View details for Web of Science ID A1997WQ43400001

• Momentum, temperature, and doping dependence of photoemission lineshape and implications for the nature of the pairing potential in high-T-c superconducting materials PHYSICAL REVIEW LETTERS Shen, Z. X., Schrieffer 1997; 78 (9): 1771–74

  View details for DOI 10.1103/PhysRevLett.78.1771

  View details for Web of Science ID A1997WL50600042

• Superconducting-gap anisotropy in YBa2CU3O7-delta: Photoemission results on untwinned crystals PHYSICAL REVIEW B Schabel, M. C., Park, C. H., Matsuura, A., Shen, Z. X., Bonn, D. A., Liang, R. X., Hardy, W. N. 1997; 55 (5): 2796–99

  View details for DOI 10.1103/PhysRevB.55.2796

  View details for Web of Science ID A1997WG88600029

• Electron-spectroscopy study of correlation mechanisms in CuGeO3 single crystals PHYSICAL REVIEW B Parmigiani, F., Sangaletti, L., Goldoni, A., delPennino, U., Kim, C., Shen, Z. X., Revcolevschi, A., Dhalenne, G. 1997; 55 (3): 1459–68

  View details for DOI 10.1103/PhysRevB.55.1459

  View details for Web of Science ID A1997WF30300039

• Excitation gap in the normal and superconducting state of underdoped Bi2Sr2Ca1-xDyxCu2O8+delta thin film and single crystals 7th International Conference on Muon Spin Rotation, Relaxation, Resonance Shen, Z. X., Harris, J. M., Loeser, A. G. SPRINGER. 1997: 13–25

  View details for Web of Science ID A1997XB05400002

• Rapid suppression of the superconducting gap in overdoped Bi2Sr2CaCu2O8+delta PHYSICAL REVIEW B White, P. J., Shen, Z. X., Kim, C., Harris, J. M., Loeser, A. G., Fournier, P., Kapitulnik, A. 1996; 54 (22): 15669-15672

  View details for Web of Science ID A1996VX71800022

• Observation of spin-charge separation in one-dimensional SrCuO2 PHYSICAL REVIEW LETTERS Kim, C., Matsuura, A. Y., Shen, Z. X., Motoyama, N., Eisaki, H., Uchida, S., Tohyama, T., Maekawa, S. 1996; 77 (19): 4054-4057

  View details for Web of Science ID A1996VQ14700029

• Electronic structure momentum dependence of Bi2Sr2CaCu2O8+delta in the normal and superconducting state JOURNAL OF SUPERCONDUCTIVITY Loeser, A. G., Shen, Z. X., Dessau, D. S. 1996; 9 (4): 373-378

  View details for Web of Science ID A1996VK55100008

• Excitation Gap in the Normal State of Underdoped Bi2Sr2CaCu2O8+delta Science (New York, N.Y.) Loeser, A. G., Shen, Z., Dessau, D. S., Marshall, D. S., Park, C. H., Fournier, P., Kapitulnik, A. 1996; 273 (5273): 325-9

  Abstract

  Angle-resolved photoemission experiments reveal evidence of an energy gap in the normal state excitation spectrum of the cuprate superconductor Bi2Sr2CaCu2O8+delta. This gap exists only in underdoped samples and closes around the doping level at which the superconducting transition temperature Tc is a maximum. The momentum dependence and magnitude of the gap closely resemble those of the dx2-y2 gap observed in the superconducting state. This observation is consistent with results from several other experimental techniques, which also indicate the presence of a gap in the normal state. Some possible theoretical explanations for this effect are reviewed.

  View details for PubMedID 8662512

• Excitation gap in the normal state of underdoped Bi2Sr2CaCu2O8+delta SCIENCE Loeser, A. G., Shen, Z. X., Dessau, D. S., Marshall, D. S., Park, C. H., Fournier, P., Kapitulnik, A. 1996; 273 (5273): 325-329

  View details for Web of Science ID A1996UY20200029

• Complete band-structure determination of the quasi-two-dimensional Fermi-liquid reference compound TiTe2 PHYSICAL REVIEW B Claessen, R., Anderson, R. O., Gweon, G. H., Allen, J. W., Ellis, W. P., Janowitz, C., Olson, C. G., Shen, Z. X., Eyert, Skibowski, M., Friemelt, K., Bucher, E., Hufner, S. 1996; 54 (4): 2453–65

  View details for DOI 10.1103/PhysRevB.54.2453

  View details for Web of Science ID A1996VB24900032

  View details for PubMedID 9986092

• Unconventional electronic structure evolution with hole doping in Bi2Sr2CaCu2O8+delta: Angle-resolved photoemission results PHYSICAL REVIEW LETTERS Marshall, D. S., Dessau, D. S., Loeser, A. G., Park, C. H., Matsuura, A. Y., Eckstein, J. N., Bozovic, I., Fournier, P., Kapitulnik, A., SPICER, W. E., Shen, Z. X. 1996; 76 (25): 4841-4844

  View details for Web of Science ID A1996UR09500048

• Doping dependence of Bi2Sr2CaCu2O8+delta in the normal state International Symposium on Frontiers of High -T(c) Superconductivity Loeser, A. G., Dessau, D. S., Shen, Z. X. ELSEVIER SCIENCE BV. 1996: 208–13

  View details for Web of Science ID A1996UW98600047

• Evolution of the electronic structure with doping in Bi2Sr2CaCu2O8+delta - Angle resolved photoemission results 11th International Conference on Vacuum Ultraviolet Radiation Physics (VUV-11 Conference) Dessau, D. S., Marshall, D. S., Loeser, A. G., Park, C. H., Matsuura, A. Y., Shen, Z. X., Fournier, P., Kapitulnik, A., Kishio, K., Eckstein, J., Bozovic, I. ELSEVIER SCIENCE BV. 1996: 167–170

  View details for Web of Science ID A1996UT32200039

• Electronic structure and the metal-insulator transition in Ni S 2 − x Se x PHYSICAL REVIEW B Matsuura, A., Shen, Z., Dessau, D., Park, C., Thio, T., Bennett, J., Jepsen, O. 1996; 53 (12)
• Anomalous Energy Gap in the Normal and Superconducting State of Underdoped Bi~2Sr~2Ca~1~-~xDy~xCu~2O~8~ ~ ︠Thin Film and Single Crystals Shen, Z., Harris, J., Loeser, A. World Scientific. River Edge, N.J.. 1996 240–243
• Anomalous superconducting state gap size versus T c behavior in underdoped Bi 2 Sr 2 Ca 1 − x Dy x Cu 2 O 8 δ Phys. Rev. B Harris, J., Shen, Z., White, P., Marshall, D., Schabel, M., Eckstein, J., Bozovic, I. 1996; 54 (22)
• Angle-resolved photoemission of quasi-one-dimensional metals: Evidence for Luttinger liquid behavior 6th International Conference on Electron Spectroscopy (ICES 6) Claessen, R., Gweon, G. H., Reinert, F., Allen, J. W., Ellis, W. P., Shen, Z. X., Olson, C. G., Schneemeyer, L. F., Levy, F. ELSEVIER SCIENCE BV. 1995: 121–126

  View details for Web of Science ID A1995UC82800017

• Band mapping of the model insulator Sr2CuO2Cl2 - Dispersion of a single hole in an antiferromagnetic background Conference on Spectroscopies in Novel Superconductors Wells, B. O., Shen, Z. X., Matsuura, A., King, D. M., Kastner, M. A., Greven, M., Birgeneau, R. J. PERGAMON-ELSEVIER SCIENCE LTD. 1995: 1871–74

  View details for Web of Science ID A1995TL54700089

• Special issue - Spectroscopies in novel superconductors - Preface JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS Shen, Z. X., Liebenberg, D., Bansil, A. 1995; 56 (12): R15–R16

  View details for DOI 10.1016/0022-3697(96)80004-7

  View details for Web of Science ID A1995TL54700001

• ANGLE-RESOLVED PHOTOEMISSION SPECTROSCOPY STUDY OF BI2SR2CACU2O8+DELTA THIN-FILMS PHYSICAL REVIEW B Marshall, D. S., Dessau, D. S., King, D. M., Park, C. H., Matsuura, A. Y., Shen, Z. X., SPICER, W. E., Eckstein, J. N., Bozovic, I. 1995; 52 (17): 12548-12551

  View details for Web of Science ID A1995TD72400021

• INTERFACE STRUCTURE AND PERPENDICULAR MAGNETIC-ANISOTROPY IN PT/CO MULTILAYERS JOURNAL OF APPLIED PHYSICS Bertero, G. A., Sinclair, R., Park, C. H., Shen, Z. X. 1995; 77 (8): 3953-3959

  View details for Web of Science ID A1995QU38700053

• ELECTRONIC-STRUCTURE AND PHOTOEMISSION-STUDIES OF LATE TRANSITION-METAL OXIDES - MOTT INSULATORS AND HIGH-TEMPERATURE SUPERCONDUCTORS PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS Shen, Z. X., Dessau, D. S. 1995; 253 (1-3): 2-162

  View details for Web of Science ID A1995QK06300001

• E VERSUS K RELATIONS AND MANY-BODY EFFECTS IN THE MODEL INSULATING COPPER-OXIDE SR2CUO2CL2 PHYSICAL REVIEW LETTERS Wells, B. O., Shen, Z. X., Matsuura, A., King, D. M., Kastner, M. A., Greven, M., Birgeneau, R. J. 1995; 74 (6): 964-967

  View details for Web of Science ID A1995QE48700034

• PHOTOEMISSION-STUDIES OF HIGH-T-C SUPERCONDUCTORS - THE SUPERCONDUCTING GAP SCIENCE Shen, Z. X., SPICER, W. E., King, D. M., Dessau, D. S., Wells, B. O. 1995; 267 (5196): 343-350

  Abstract

  Over the last several years there have been great improvements in the energy resolution and detection efficiency of angle-resolved photoemission spectroscopy. These improvements have made it possible to discover a number of fascinating features in the electronic structure of the high transition temperature (T(c)) superconductors: apparently bandlike Fermi surfaces, flat-band saddle points, and nested Fermi surface sections. Recent work suggests that these features, previously thought explainable only by one-electron band theory, may be better understood with a many-body approach. Furthermore, other properties of the high-T(c) superconductors, which are difficult to understand with band theory, are well described using a many-body picture. Angle-resolved photoemission spectroscopy has also been used to investigate the nature of the superconducting pairing state, revealing an anisotropic gap consistent with a d-wave order parameter and fueling the current debate over s-wave versus d-wave superconductivity.

  View details for Web of Science ID A1995QC27300026

  View details for PubMedID 17837480

• DIRECT OBSERVATION OF A VERY SHARP SPECTRAL FEATURE AT THE BAND EDGE OF FeSi PHYSICAL REVIEW B 52 Park, C., Shen, Z., Loeser, A., Dessau, D., Aeppli, G., Fisk, Z. 1995
• Signature of Superfluid Density in the Single-Particle Excitation Spectrum of Bi2Sr2CaCu2O8+δ Feng, D., Lu, D., Shen, K., Kim, C., Eisaki, H., Damascelli, A., Yoshizaki, R., Shimoyama, J., Kishio, K., Gu, G., Oh, S., Andrus, A., O'Donnell, J., Eckstein, J., Shen, Z. Quaternary Research. 1995 341
• ELECTRONIC STRUCTURE EVOLUTION FROM MOTT INSULATOR TO SUPERCONDUCTOR--AN ANGLE-RESOVED PHOTOEMISSION INVESTIGATION Journal of Physics and Chemistry of Solids King, D., Dessau, D., Loeser, A., Shen, Z., Wells, B. 1995; 56 (12): 1865-1869
• PHOTOEMISSION STUDIES OF NOVEL SUPERCONDUCTORS China Center of Advanced Science and Technology Matthias, C., Shen, Z. 1995: 81–113
• ELECTRONIC-STRUCTURE OF K2NIF4 PHYSICAL REVIEW B Sangaletti, L., Parmigiani, F., Ratner, E., Shen, Z. X., CHEMELLI, C., JEPSEN, O. 1994; 50 (24): 17854-17866

  View details for Web of Science ID A1994QB02200007

• SYMMETRY OF THE GAP IN BI2212 FROM PHOTOEMISSION SPECTROSCOPY - REPLY PHYSICAL REVIEW LETTERS Dessau, D. S., Shen, Z. X., Wells, B. O. 1994; 73 (22): 3045-3045

  View details for Web of Science ID A1994PT99700032

• FERMIOLOGY AND SUPERCONDUCTING GAP ANISOTROPY OF CUPRATE SUPERCONDUCTORS 20th International Conference on Low Temperature Physics Shen, Z. X. ELSEVIER SCIENCE BV. 1994: 632–35

  View details for Web of Science ID A1994NG61500078

• IN EXPLAINING HIGH-T(C) IS D-WAVE A WASHOUT - REPLY PHYSICS TODAY Shen, Z. X. 1994; 47 (2): 120-120

  View details for Web of Science ID A1994NA80800018

• PHOTOEMISSION-STUDIES OF THE BI-SR-CA-CU-O VALENCE-BAND JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Loeser, A. G., Shen, Z. X., Dessau, D. S., SPICER, W. E. 1994; 66 (3-4): 359-385

  View details for Web of Science ID A1994MX84300010

• FERMI SURFACES AND ENERGY GAPS OF HIGH-TEMPERATURE SUPERCONDUCTORS Conference on Oxide Superconductor Physics and Nano-Engineering Shen, Z. X., Dessau, D. S. SPIE - INT SOC OPTICAL ENGINEERING. 1994: 64–69

  View details for Web of Science ID A1994BB27H00008

• In Explaining High TC, is D-Wave a Washout? Physics Today Anderson, P. W., Pines, D., Scalapino, D. J., Shen, Z. 1994; 47 (2): 11

  View details for DOI 10.1063/1.2808399

• OBSERVATION OF A SADDLE POINT SINGULARITY IN Bi2201 AND ITS IMPLICATIONS FOR NORMAL AND SUPERCONDUCTING STATE PROPERTIES King, D., Shen, Z., Dessau, D., Marshall, D., Park, C., Spicer, W., Peng, J., Li, Z., Greene, R. Physical Review Letters. 1994 ; 73 3298
• ANOMALOUSLY LARGE GAP ANISOTROPY IN THE A-B PLANE OF BI2SR2CACUZO8+DELTA - REPLY PHYSICAL REVIEW LETTERS Dessau, D. S., Shen, Z. X., Marshall, D. M. 1993; 71 (25): 4278-4278

  View details for Web of Science ID A1993MM25400050

• KEY FEATURES IN THE MEASURED BAND-STRUCTURE OF BI2SR2CACU2O8+DELTA - FLAT BANDS AT E(F) AND FERMI-SURFACE NESTING PHYSICAL REVIEW LETTERS Dessau, D. S., Shen, Z. X., King, D. M., Marshall, D. S., Lombardo, L. W., DICKINSON, P. H., Loeser, A. G., DiCarlo, J., Park, C. H., Kapitulnik, A., SPICER, W. E. 1993; 71 (17): 2781-2784

  View details for Web of Science ID A1993MD94700026

• RECENT RESULTS FROM BI2SR2CACU2O8 AND ND2-XCEXCUO4 Conference on Spectroscopies in Novel Superconductors Shen, Z. X., Dessau, D. S., Wells, B. O., King, D. M. PERGAMON-ELSEVIER SCIENCE LTD. 1993: 1169–76

  View details for Web of Science ID A1993MN59400019

• STRUCTURAL INFORMATION ON Y-IONS IN C82 FROM EXAFS EXPERIMENTS CHEMICAL PHYSICS LETTERS Park, C. H., Wells, B. O., DiCarlo, J., Shen, Z. X., Salem, J. R., Bethune, D. S., Yannoni, C. S., Johnson, R. D., deVries, M. S., Booth, C., Bridges, F., Pianetta, P. 1993; 213 (1-2): 196-201

  View details for Web of Science ID A1993LZ69200032

• FERMI-SURFACE AND ELECTRONIC-STRUCTURE OF ND2-XCEXCUO4-DELTA PHYSICAL REVIEW LETTERS King, D. M., Shen, Z. X., Dessau, D. S., Wells, B. O., SPICER, W. E., Arko, A. J., Marshall, D. S., DiCarlo, J., Loeser, A. G., Park, C. H., Ratner, E. R., Peng, J. L., Li, Z. Y., Greene, R. L. 1993; 70 (20): 3159-3162

  View details for Web of Science ID A1993LB78400047

• ANOMALOUSLY LARGE GAP ANISOTROPY IN THE A-B PLANE OF BI2SR2CACU2O8+DELTA PHYSICAL REVIEW LETTERS Shen, Z. X., Dessau, D. S., Wells, B. O., King, D. M., SPICER, W. E., Arko, A. J., Marshall, D., Lombardo, L. W., Kapitulnik, A., Dickinson, P., Doniach, S., DiCarlo, J., Loeser, A. G., Park, C. H. 1993; 70 (10): 1553-1556

  View details for Web of Science ID A1993KQ41400050

• HIGH-ENERGY RESOLUTION ARPES MEASUREMENTS OF THE NORMAL AND SUPERCONDUCTING STATES OF BI2SR2CACU2O8+DELTA SYMP ON APPLICATIONS OF SYNCHROTON RADIATION TECHNIQUES TO MATERIALS SCIENCE, AT THE 1993 SPRING MEETING OF THE MATERIALS RESEARCH SOC Dessau, D. S., Shen, Z. X., King, D. M., Wells, B. O., Marshall, D. S., Lombardo, L. W., DICKINSON, P. H., DiCarlo, J., Park, C. H., Loeser, A. G., Kapitulnik, A., SPICER, W. E., Arko, A. J. MATERIALS RESEARCH SOC. 1993: 187–192

  View details for Web of Science ID A1993BY84N00030

• High-Resolution Photoemission Study of High-Temperature Superconductors OCPA Newsletter Shen, Z. 1993
• High energy resolution ARPES measurements of the normal and superconducting states of Bi2Sr2CaCu2O8+δ Los Alamos National Lab., LA-UR-93-2693; CONF-930405-34 Dessau, D., King, D., Shen, Z. 1993
• PHOTOEMISSION STUDY OF SINGLE CRYSTAL Bi2Sr1.9Pr0.1CuO6  Physical Review B Ratner, E., Shen, Z., Dessau, D., Wells, B., Marshall, D., King, D., Spicer, W., Peng, J., Li, Z., Greene, R. 1993: 10482
• K-DEPENDENT SUPERCONDUCTING GAP ANISOTROPY IN THE A-B-PLANE AND ITS IMPLICATIONS JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS SHEN, Z. X. 1992; 53 (12): 1583–87

  View details for DOI 10.1016/0022-3697(92)90147-6

  View details for Web of Science ID A1992KE86300017

• ANGLE-RESOLVED-PHOTOEMISSION STUDY OF BI2SR2CACU2O8+8+DELTA - METALLICITY OF THE BI-O PLANE - REPLY PHYSICAL REVIEW LETTERS Wells, B. O., Shen, Z. X., Dessau, D. S., SPICER, W. E. 1992; 68 (3): 417-417

  View details for Web of Science ID A1992GZ96700046

• PHOTOEMISSION-STUDY OF SINGLE-CRYSTAL C-60 SYMP ON NOVEL FORMS OF CARBON Wu, J., Shen, Z. X., Dessau, D. S., Cao, R., Marshall, D. S., Pianetta, P., LINDAU, I., Yang, X., Terry, J., King, D. M., Wells, B. O. MATERIALS RESEARCH SOC. 1992: 235–240

  View details for Web of Science ID A1992BX58Q00034

• ANGLE-RESOLVED PHOTOEMISSION OF C60 proceedings of the 10th VUV conference, edited by F.J. Wuillenmier, Y. Petroff, and I. Nenner, Shen, Z. 1992: 301
• ELECTRONIC STRUCTURE OF SINGLE CRYSTAL C60 Physica C: Superconductivity Wu, J., Shen, Z., Cao, R., Dessau, D., Yang, X., Pianetta, P., Marshall, D., Wells, B., King, D., Terry, J., Elloway, D., Wendt, H., Brown, C., Hunzikar, H., de Vries, M. 1992; 197 (3-4): 251-260
• NATURE OF THE HIGH-BINDING-ENERGY DIP IN THE LOW-TEMPERATURE PHOTOEMISSION SPECTRA OF Bi2212 Phys. Rev. Dessau, D., Shen, Z., Wells, B., Spicer, W., Arko, A., Lambardo, L., Mitzi, D., Kapitulnik, A. 1992
• EVIDENCE FOR IN-PLANE ANISOTROPY OF THE SUPERCONDUCTING GAP IN Bi2Sr2CaCu2O8  Phys. Rev Wells, B., Shen, Z., Dessau, D., Spicer, W., Arko, A., Mitzi, D., Lambardo, L., Kapitulnik, A. 1992
• ANGLE RESOLVED PHOTOEMISSION STUDY OF BI2SR2CACU208 8 DELTA-METALLICITY OF THE BI-O PLANE Reply Physicial Review Letters Wells, B., Shen, Z., Dessau, D., Spicer, W. 1992: 417-417
• ELECTRONIC-STRUCTURE OF NIO - CORRELATION AND BAND EFFECTS PHYSICAL REVIEW B Shen, Z. X., LIST, R. S., Dessau, D. S., Wells, B. O., JEPSEN, O., Arko, A. J., BARTTLET, R., Shih, C. K., Parmigiani, F., Huang, J. C., LINDBERG, P. A. 1991; 44 (8): 3604-3626

  View details for Web of Science ID A1991GC99500011

• ANGLE RESOLVED PHOTOEMISSION OF NIO(001) SOLID STATE COMMUNICATIONS Shen, Z. X., LIST, R. S., Dessau, D. S., Arko, A. J., BARTTLET, R., JEPSEN, O., Wells, B. O., Parmigiani, F. 1991; 79 (7): 623-628

  View details for Web of Science ID A1991GE20000014

• THE GOLD HIGH-TEMPERATURE SUPERCONDUCTOR INTERFACE - METALLICITY OF THE NEAR-SURFACE REGION AND A SEARCH FOR THE PROXIMITY EFFECT 37TH NATIONAL SYMP OF THE AMERICAN VACUUM SOC Dessau, D. S., Shen, Z. X., Wells, B. O., SPICER, W. E., LIST, R. S., Arko, A. J., BARTLETT, R. J., Olson, C. G., Mitzi, D. B., Eom, C. B., Kapitulnik, A., Geballe, T. H. AMER INST PHYSICS. 1991: 383–89

  View details for Web of Science ID A1991FR76100002

• ANOMALOUS SPECTRAL WEIGHT TRANSFER AT THE SUPERCONDUCTING TRANSITION OF BI2SR2CACU2O8+DELTA PHYSICAL REVIEW LETTERS Dessau, D. S., Wells, B. O., Shen, Z. X., SPICER, W. E., Arko, A. J., LIST, R. S., Mitzi, D. B., Kapitulnik, A. 1991; 66 (16): 2160-2163

  View details for Web of Science ID A1991FH36600028

• O 1S CORE LEVELS IN BI2SR2CACU2O8+DELTA SINGLE-CRYSTALS PHYSICAL REVIEW B Parmigiani, F., Shen, Z. X., Mitzi, D. B., LINDAU, I., SPICER, W. E., Kapitulnik, A. 1991; 43 (4): 3085-3090

  View details for Web of Science ID A1991FF08300077

• SPIN-DEPENDENT ELECTRON ATTENUATION BY TRANSMISSION THROUGH THIN FERROMAGNETIC-FILMS PHYSICAL REVIEW LETTERS PAPPAS, D. P., KAMPER, K. P., MILLER, B. P., HOPSTER, H., FOWLER, D. E., BRUNDLE, C. R., LUNTZ, A. C., SHEN, Z. X. 1991; 66 (4): 504–7

  View details for DOI 10.1103/PhysRevLett.66.504

  View details for Web of Science ID A1991EU78600028

• SPECTRAL WEIGHT CHANGES AT THE SUPERCONDUCTING TRANSITION OF BI2SR2CACU2O8+DELTA WORKSHOP ON FERMIOLOGY OF HIGH-TC SUPERCONDUCTORS Dessau, D. S., Shen, Z. X., Wells, B. O., SPICER, W. E., Arko, A. J. PERGAMON-ELSEVIER SCIENCE LTD. 1991: 1401–9

  View details for Web of Science ID A1991GY55300017

• Magnetism of ultrathin films of Fe on Cu(100) Journal of Applied Physics Pappas, D., Kamper, K., Miller, B., Hopster, H., Fowler, D., Brundle, C., Luntz, A., Shen, Z. 1991; 69 (8): 5209
• SPIN POLARIZED PHOTOEMISSION FROM Fe on Cu(100) Magnetic Surfaces, Thin Films, and Multilayers Symposium. Pappas, D., Kamper, K., Miller, B., Hopster, H., Fowler, D., Brundle, C., Luntz, A., Shen, Z. 1991
• A SEARCH FOR A PROXIMITY EFFECT INDUCED GAP IN GOLD/HIGH Tc JUNCTIONS Dessau, D., Wells, B., Shen, Z., Spicer, W., Arko, A., List, R., Olson, C., Eom, C., Mitzi, D., Kapitulnik, A., Geballe, T. Appl. Phys. Lett. . 1991 58, 1332
• EVIDENCE for CHEMICAL POTENTIAL SHIFT WITH DOPING IN Bi2Sr2CaCu2O8+DELTA Phys. Rev. B Shen, Z., Dessau, D., Wells, B., Spicer, W., Olson, C., Mitzi, D., List, R., Arko, A. 1991; 44 (21): 12098-12101

  View details for DOI 10.1103/PhysRevB.44.12098

• ELECTRONIC-STRUCTURE AND THE SUPERCONDUCTING GAP OF BI2SR2CACU2O8+DELTA WORKSHOP ON THE ELECTRONIC STRUCTURE AND MECHANISMS FOR HIGH-TEMPERATURE SUPERCONDUCTIVITY Shen, Z. X., Dessau, D. S., Wells, B. O. PLENUM PRESS DIV PLENUM PUBLISHING CORP. 1991: 113–118

  View details for Web of Science ID A1991BW01V00014

• ANGLE-RESOLVED-PHOTOEMISSION STUDY OF BI2SR2CACU2O8+DELTA - METALLICITY OF THE BI-O PLANE PHYSICAL REVIEW LETTERS Wells, B. O., Shen, Z. X., Dessau, D. S., SPICER, W. E., Olson, C. G., Mitzi, D. B., Kapitulnik, A., LIST, R. S., Arko, A. 1990; 65 (24): 3056-3059

  View details for Web of Science ID A1990EL84000035

• PHOTOEMISSION-STUDY OF CUO AND CU2O SINGLE-CRYSTALS PHYSICAL REVIEW B Shen, Z. X., LIST, R. S., Dessau, D. S., Parmigiani, F., Arko, A. J., Bartlett, R., Wells, B. O., LINDAU, I., SPICER, W. E. 1990; 42 (13): 8081-8085

  View details for Web of Science ID A1990EG48800051

• LOCAL SINGLET FOR CUO AND ND2CUO4 PHYSICAL REVIEW B Gunnarsson, O., JEPSEN, O., Shen, Z. X. 1990; 42 (13): 8707-8709

  View details for Web of Science ID A1990EG49000072

• ELECTRONIC-STRUCTURE OF THE GOLD BI2SR2CACU2O8 AND GOLD EUBA2CU3O7-DELTA INTERFACES AS STUDIED BY PHOTOEMISSION SPECTROSCOPY APPLIED PHYSICS LETTERS Dessau, D. S., Shen, Z. X., Wells, B. O., SPICER, W. E., LIST, R. S., Arko, A. J., BARTLETT, R. J., Fisk, Z., Cheong, S. W., Mitzi, D. B., Kapitulnik, A., Schirber, J. E. 1990; 57 (3): 307-309

  View details for Web of Science ID A1990DN53800035

• PHOTOEMISSION-STUDY OF COO PHYSICAL REVIEW B Shen, Z. X., Allen, J. W., LINDBERG, P. A., Dessau, D. S., Wells, B. O., Borg, A., Ellis, W., Kang, J. S., Oh, S. J., LINDAU, I., SPICER, W. E. 1990; 42 (3): 1817-1828

  View details for Web of Science ID A1990DQ81600037

• YB MEAN VALENCE IN CHEMICALLY COMPRESSED YB1-XSCXAL2 PSEUDOBINARY ALLOYS - AN X-RAY ABSORPTION-SPECTROSCOPY INVESTIGATION SOLID STATE COMMUNICATIONS Sancrotti, M., ABBATI, I., Puppin, E., Shen, Z. X., LINDAU, I., Eggenhoffner, R., Iandelli, A., Olcese, G. L. 1990; 74 (10): 1131-1135

  View details for Web of Science ID A1990DJ02600022

• YB VALENCE IN YB1-XCAXAL2 PSEUDOBINARY ALLOYS VIA YB LIII X-RAY ABSORPTION-SPECTROSCOPY SOLID STATE COMMUNICATIONS Eggenhoffner, R., Sancrotti, M., ABBATI, I., Puppin, E., Shen, Z. X., LINDAU, I., Iandelli, A., Olcese, G. L. 1990; 74 (9): 1009-1012

  View details for Web of Science ID A1990DH74400029

• ASPECTS OF THE CORRELATION-EFFECTS, ANTIFERROMAGNETIC ORDER, AND TRANSLATIONAL SYMMETRY OF THE ELECTRONIC-STRUCTURE OF NIO AND COO PHYSICAL REVIEW LETTERS Shen, Z. X., Shih, C. K., JEPSEN, O., SPICER, W. E., LINDAU, I., Allen, J. W. 1990; 64 (20): 2442-2445

  View details for Web of Science ID A1990DC93700027

• POLARIZED RESONANCE PHOTOEMISSION FOR ND2CUO4 PHYSICAL REVIEW B Gunnarsson, O., Allen, J. W., JEPSEN, O., FUJIWARA, T., Andersen, O. K., Olsen, C. G., Maple, M. B., Kang, J. S., Liu, L. Z., Park, J. H., Anderson, R. O., Ellis, W. P., Liu, R., Markert, J. T., Dalichaouch, Y., Shen, Z. X., LINDBERG, P. A., Wells, B. O., Dessau, D. S., Borg, A., LINDAU, I., SPICER, W. E. 1990; 41 (7): 4811-4814

  View details for Web of Science ID A1990CU14000125

• PHOTOEMISSION-STUDIES OF HIGH-TEMPERATURE SUPERCONDUCTORS SURFACE SCIENCE REPORTS LINDBERG, P. A., Shen, Z. X., SPICER, W. E., LINDAU, I. 1990; 11 (1-4): 1-?

  View details for Web of Science ID A1990CW13300001

• Reply to the ‘‘Comment on ‘Valence-band states in Bi 2 (Ca,Sr,La ) 3 Cu 2 O 8 .’ ’’ Phys. Rev. B 40, 5169 (1989) Wells, B., Shen, Z., Spicer, W. 1990; 42 (7): 4785

  View details for DOI 10.1103/PhysRevB.42.4785

• Au overlayer on YBa2Cu3O7 and Bi2Sr2CaCu2O8 Dessau, D., List, R., Shen, Z., Arko, A., Barttlet, R., Wells, B., Spicer, W. Applied Physics Letter 57, 307 . 1990
• INTERACTION OF OVERLAYERS OF AI AND Rb WITH SINGLE CRYSTALLINE SURFACES OF BI2Sr2CaCu2O8 J. of Appl. Phys. Lindberg, P., Wells, B., Shen, Z., Dessau, D., Mitzi, D., Lindau, I., Spicer, W., Kapitulnik, A. 1990: 67, 2667
• ELECTRONIC STRUCTURE OF BaBiO3 AVS/AIP conference proceeding Shen, Z., Lindberg, P., Wells, B., Dessau, D., Borg, A., Lindau, I., Spicer, W., Ellis, W., Kwei, G., Ott, K., Kang, J., Allen, J. 1990: No.200, page 30, 1990, edited by R.L. Stockbauer et al.,
• ELECTRONIC-STRUCTURE OF MONOCLINIC BABIO3 3RD TOPICAL SYMP OF THE AMERICAN VACUUM SOC - HIGH TC SUPERCONDUCTING THIN FILMS : PROCESSING, CHARACTERIZATION AND APPLICATIONS Shen, Z. X., LINDBERG, P. A., Wells, B. O., Dessau, D. S., Borg, A., LINDAU, I., SPICER, W. E., Ellis, W. P., Kwei, G. H., Ott, K. C., Kang, J. S., Allen, J. W. AIP PRESS. 1990: 30–35

  View details for Web of Science ID A1990BQ46K00004

• NATURE OF THE VALENCE BAND STATES IN BI2(CA,SR,LA)3CU2O8 3RD TOPICAL SYMP OF THE AMERICAN VACUUM SOC - HIGH TC SUPERCONDUCTING THIN FILMS : PROCESSING, CHARACTERIZATION AND APPLICATIONS Wells, B. O., LINDBERG, P. A., Shen, Z. X., Dessau, D. S., SPICER, W. E., LINDAU, I., Mitzi, D. B., Kapitulnik, A. AIP PRESS. 1990: 36–41

  View details for Web of Science ID A1990BQ46K00005

• ELECTRON-SPECTROSCOPY OF HEAVY-FERMION MATERIALS 9TH INTERNATIONAL CONF ON VACUUM ULTRAVIOLET RADIATION PHYSICS ( VUV 9 ) Allen, J. W., Kang, J. S., Liu, L. Z., Gunnarsson, O., Christensen, N. E., Andersen, O. K., Maple, M. B., Torikachvili, M. S., Koelling, D. D., Ellis, W. P., Pate, B. B., Shen, Z. X., Yeh, J. J., LINDAU, I. IOP PUBLISHING LTD. 1990: 232–238

  View details for Web of Science ID A1990DN39400034

• ELECTRONIC-STRUCTURE OF SINGLE CRYSTALLINE BI2(SR,CA,LA)3CU2O8 INTERNATIONAL CONF ON MATERIALS AND MECHANISMS OF SUPERCONDUCTIVITY : HIGH TEMPERATURE SUPERCONDUCTORS 2 LINDBERG, P. A., Shen, Z. X., Dessau, D. S., Wells, B. O., Borg, A., Mitzi, D. B., LINDAU, I., SPICER, W. E., Kapitulnik, A. ELSEVIER SCIENCE BV. 1989: 1313–1314

  View details for Web of Science ID A1989CG49000222

• THE ELECTRONIC-STRUCTURE OF PB2SR2PRCU3O8 AS STUDIED BY RESONANT PHOTOEMISSION SPECTROSCOPY INTERNATIONAL CONF ON MATERIALS AND MECHANISMS OF SUPERCONDUCTIVITY : HIGH TEMPERATURE SUPERCONDUCTORS 2 Dessau, D. S., Shen, Z. X., LINDBERG, P. A., Wells, B. O., Borg, A., LINDAU, I., SPICER, W. E., Waszczak, J. V., Schneemeyer, L. F. ELSEVIER SCIENCE BV. 1989: 1373–1374

  View details for Web of Science ID A1989CG49000252

• ANGLE-RESOLVED PHOTOEMISSION-STUDY OF NIO AND COO INTERNATIONAL CONF ON MATERIALS AND MECHANISMS OF SUPERCONDUCTIVITY : HIGH TEMPERATURE SUPERCONDUCTORS 2 Shen, Z. X., LINDBERG, P. A., Shih, C. K., SPICER, W. E., LINDAU, I. ELSEVIER SCIENCE BV. 1989: 1311–1312

  View details for Web of Science ID A1989CG49000221

• PHOTOEMISSION-STUDY OF ABSORPTION MECHANISMS IN BI2.0SR1.8CA0.8LA0.3CU2.1O8+DELTA, BABIO3, AND ND1.85CE0.15CUO4 PHYSICAL REVIEW B LINDBERG, P. A., Shen, Z. X., Wells, B. O., Dessau, D. S., Ellis, W. P., Borg, A., Kang, J. S., Mitzi, D. B., LINDAU, I., SPICER, W. E., Kapitulnik, A. 1989; 40 (13): 8840-8843

  View details for Web of Science ID A1989AX80800030

• PHOTOEMISSION-STUDY OF THE ELECTRONIC-STRUCTURE (PR0.2LA0.8)(BA1.875LA0.125)CU3O7-DELTA SYSTEM SOLID STATE COMMUNICATIONS LINDBERG, P. A., Shen, Z. X., LINDAU, I., SPICER, W. E., Mitzi, D. B., Kapitulnik, A. 1989; 72 (6): 575-578

  View details for Web of Science ID A1989AZ31600013

• ELECTRONIC-STRUCTURE OF CLEAN AND AG-COVERED SINGLE-CRYSTALLINE BI2SR2CUO6 PHYSICAL REVIEW B LINDBERG, P. A., Shen, Z. X., Wells, B. O., Mitzi, D. B., LINDAU, I., SPICER, W. E., Kapitulnik, A. 1989; 40 (13): 8769-8773

  View details for Web of Science ID A1989AX80800018

• ELECTRONIC-STRUCTURE OF PB2SR2PRCU3O8 AS STUDIED BY RESONANT PHOTOEMISSION SPECTROSCOPY PHYSICAL REVIEW B Dessau, D. S., Shen, Z. X., LINDBERG, P. A., Wells, B. O., Borg, A., LINDAU, I., SPICER, W. E., Waszczak, J. V., Schneemeyer, L. F. 1989; 40 (10): 6726-6730

  View details for Web of Science ID A1989AU62900033

• PHOTOEMISSION-STUDY OF MONOCLINIC BABIO3 PHYSICAL REVIEW B Shen, Z. X., LINDBERG, P. A., Wells, B. O., Dessau, D. S., Borg, A., LINDAU, I., SPICER, W. E., Ellis, W. P., Kwei, G. H., Ott, K. C., Kang, J. S., Allen, J. W. 1989; 40 (10): 6912-6918

  View details for Web of Science ID A1989AU62900057

• SPECTROSCOPIC EVIDENCE OF TWO-DIMENSIONAL CHARACTER OF THE 90-K BI2(SR,LA,CA)3CU2O8 SUPERCONDUCTORS APPLIED PHYSICS LETTERS LINDBERG, P. A., Shen, Z. X., Wells, B. O., Dessau, D. S., Borg, A., LINDAU, I., SPICER, W. E., Mitzi, D. B., Kapitulnik, A. 1989; 55 (11): 1141-1143

  View details for Web of Science ID A1989AN83100031

• THE ELECTRONIC-STRUCTURE OF BI2.0SR1.8LA0.3CA0.8CU2.1O8+DELTA-SUPERCONDUCTORS STUDIED USING ULTRAVIOLET AND X-RAY PHOTOELECTRON-SPECTROSCOPY PHYSICA C LINDBERG, P. A., Shen, Z. X., Dessau, D. S., Wells, B. O., Borg, A., Ellis, W., Mitzi, D. B., LINDAU, I., SPICER, W. E., Kapitulnik, A. 1989; 159 (5): 649-653

  View details for Web of Science ID A1989AK44500016

• FERMI-LEVEL TUNING IN Y1-XUXPD3 PHYSICAL REVIEW B Kang, J. S., Allen, J. W., Maple, M. B., Torikachvili, M. S., Ellis, W. P., Pate, B. B., Shen, Z. X., Yeh, J. J., LINDAU, I. 1989; 39 (18): 13529-13532

  View details for Web of Science ID A1989AC81600062

• ELECTRONIC-STRUCTURE OF THE QUENCHED SUPERCONDUCTIVITY MATERIALS Y1-XPRXBA2CU3O7-DELTA JOURNAL OF THE LESS-COMMON METALS Kang, J. S., Allen, J. W., Shen, Z. X., Ellis, W. P., Yeh, J. J., Lee, B. W., Maple, M. B., SPICER, W. E., LINDAU, I. 1989; 148 (1-2): 121-132

  View details for Web of Science ID A1989U387400016

• PHOTOELECTRON ENERGY-LOSS STUDY OF THE BI2CASR2CU2O8 SUPERCONDUCTOR PHYSICAL REVIEW B Shen, Z. X., LINDBERG, P. A., Dessau, D. S., LINDAU, I., SPICER, W. E., Mitzi, D. B., Bozovic, I., Kapitulnik, A. 1989; 39 (7): 4295-4298

  View details for Web of Science ID A1989T686300042

• ELECTRONIC-STRUCTURE OF THE LA1+XBA2-XCU3O7+DELTA-SYSTEM STUDIED BY PHOTOELECTRON-SPECTROSCOPY SOLID STATE COMMUNICATIONS LINDBERG, P. A., Shen, Z. X., Hwang, J., Shih, C. K., LINDAU, I., SPICER, W. E., Mitzi, D. B. 1989; 69 (1): 27-31

  View details for Web of Science ID A1989R401800006

• NATURE OF THE VALENCE BAND STATES IN Bi2(SrCaLa)3Cu2O8 Phys. Rev. B 40, 5259 Wells, B., Lindberg, P., Shen, Z., Dessau, D., Lindau, I., Spicer, W., Mitzi, D., Kapitulnik, A. 1989
• ENERGY DISPERSIONS OF SINGLE CRYSTALLINE Bi2.0Sr1.8La0.3Ca0.8Cu2.1O8  SUPERCONDUCTORS DETERMINED USING ANGLE-RESOLVED PHOTOELECTRON SPECTROSCOPY Phys. Rev. B 40, 5169 (1989) Lindberg, P., Shen, Z., Dessau, D., Wells, B., Mitzi, D., Lindau, I., Spicer, W., Kapitulnik, A. 1989
• REACTION OF Rb AND OXYGEN OVERLAYERS WITH SINGLE-CRYSTALLINE Bi2CaSr2CaCu2O8 SUPERCONDUCTORS Phys. Rev. B 39, 2890 (1989) Lindberg, P., Shen, Z., Wells, B., Dessau, D., Mitzi, D., Lindau, I., Spicer, W., Kapitulnik, A. 1989
• ALUMINUM AND GOLD DEPOSITION ON CLEAVED SINGLE CRYSTALS OF Bi2CaSr2CaCu2O8 SUPERCONDUCTORS AIP/AVS Conference Proceedings 182, 391-398 (1989) Wells, B., Lindberg, P., Shen, Z., Dessau, D., Lindau, I., Spicer, W., Mitzi, D., Kapitulnik, A. 1989
• PHOTOEMISSION STUDY OF HIGH TEMPERATURE SUPERCONDUCTORS AIP/AVS Conference Proceedings, 182, 330-349 Shen, Z., Lindberg, P., Spicer, W., Lindau, I., Allen, J. 1989
• SURFACE AND ELECTRONIC STRUCTURE OF Bi-Ca-Sr-Cu-O SUPERCONDUCTORS STUDIED USING LEED, UPS, AND XPS AIP/AVS Conference Proceedings 182, 312-317, (1989) Shen, Z., Lindberg, P., Spicer, W., Soukiassian, P., Mitzi, D., Kapitulnik, A., Geballe, T. 1989
• NATURE OF THE STATES NEAR THE FERMI LEVEL OF THE LAYERED SUPERCONDUCTORS OF BI2CA1SR2CU2O8 AND BI2SR2CUO6 PHYSICAL REVIEW B Shen, Z. X., LINDBERG, P. A., Soukiassian, P., Eom, C. B., LINDAU, I., SPICER, W. E., Geballe, T. H. 1989; 39 (1): 823-826

  View details for Web of Science ID A1989R832300132

• SURFACE-STRUCTURE OF BI2SR2CACU2O8+SIGMA HIGH-TEMPERATURE SUPERCONDUCTORS STUDIED USING LOW-ENERGY ELECTRON-DIFFRACTION APPLIED PHYSICS LETTERS LINDBERG, P. A., Shen, Z. X., Wells, B. O., Mitzi, D. B., LINDAU, I., SPICER, W. E., Kapitulnik, A. 1988; 53 (25): 2563-2565

  View details for Web of Science ID A1988R375200034

• VALENCE-BAND AND CORE-LEVEL PHOTOEMISSION-STUDY OF SINGLE-CRYSTAL BI2CASR2CU2O8 SUPERCONDUCTORS PHYSICAL REVIEW B Shen, Z. X., LINDBERG, P. A., Wells, B. O., Mitzi, D. B., LINDAU, I., SPICER, W. E., Kapitulnik, A. 1988; 38 (16): 11820-11823

  View details for Web of Science ID A1988R274300040

• ELECTRONIC-STRUCTURE OF CERAMICS AND THIN-FILM SAMPLES OF HIGH-TC BI2SR2CACU2O8+DELTA SUPERCONDUCTORS - EFFECTS OF AR+ SPUTTERING, O-2 EXPOSURE, AND RB DEPOSITION APPLIED PHYSICS LETTERS LINDBERG, P. A., Soukiassian, P., Shen, Z. X., Shah, S. I., Eom, C. B., LINDAU, I., SPICER, W. E., Geballe, T. H. 1988; 53 (20): 1970-1972

  View details for Web of Science ID A1988Q840900028

• ELECTRONIC-STRUCTURE OF BI-CA-SR-CU-O SUPERCONDUCTORS STUDIED BY PHOTOELECTRON-SPECTROSCOPY PHYSICAL REVIEW B Shen, Z. X., LINDBERG, P. A., LINDAU, I., SPICER, W. E., Eom, C. B., Geballe, T. H. 1988; 38 (10): 7152-7155

  View details for Web of Science ID A1988Q552000123

• KAPPA-RESOLVED ALLOY BOWING IN PSEUDOBINARY INXGA1-XAS ALLOYS PHYSICAL REVIEW LETTERS Hwang, J., Pianetta, P., Pao, Y. C., Shih, C. K., Shen, Z. X., LINDBERG, P. A., Chow, R. 1988; 61 (7): 877-880

  View details for Web of Science ID A1988P707100029

• PHOTOEMISSION-STUDY OF THE SURFACE ELECTRONIC-STRUCTURE OF BI-CA-SR-CU-O SUPERCONDUCTORS MODIFIED BY NE SPUTTERING, AG DEPOSITION, AND HEAT-TREATMENT APPLIED PHYSICS LETTERS LINDBERG, P. A., Shen, Z. X., LINDAU, I., SPICER, W. E., Eom, C. B., Geballe, T. H. 1988; 53 (6): 529-531

  View details for Web of Science ID A1988P611900027

• PHOTOEMISSION FROM THE SI/LA INTERFACE SOLID STATE COMMUNICATIONS Puppin, E., Guyot, H., Shen, Z. X., Hwang, J., LINDAU, I. 1988; 67 (1): 23-27

  View details for Web of Science ID A1988N979100006

• THE EFFECT OF STRAIN ON THE BAND-STRUCTURE OF INXGA1-XAS JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B Hwang, J., Pianetta, P., Kubiak, G. D., Stulen, R. H., Shin, C. K., Pao, Y. C., Shen, Z. X., LINDBERG, P. A., Chow, R. 1988; 6 (4): 1234-1239

  View details for Web of Science ID A1988P729100033

• Photoemission Study Of The Surface Chemistry And The Electronic Structure Of Copper Oxide Superconducting Thin Films Proc. SPIE 0948, High-Tc Superconductivity: Thin Films and Devices Shen, Z., Yeh, J., Lindau, I., Spicer, W., Sun, J., Char, K., Missert, N., Kapitulnik, A., Geballe, T., Beasley, M. 1988
• Electronic Spectroscopy Studies of High Temperature Superconductors: Y1-xPrxBa2Cu3O7- δ The Proceedings of the International Symposium on the Electronic Structure of High Tc Superconductors Kang, J., Allen, J., Lee, B., Maple, M., Shen, Z., Yeh, J., Ellis, W., Spicer, W., Lindau, I. 1988
• ANDERSON HAMILTONIAN DESCRIPTION OF THE EXPERIMENTAL ELECTRONIC-STRUCTURE AND MAGNETIC-INTERACTIONS OF COPPER-OXIDE SUPERCONDUCTORS PHYSICAL REVIEW B Shen, Z. X., Allen, J. W., Yeh, J. J., Kang, J. S., Ellis, W., Spicer, W., LINDAU, I., Maple, M. B., DALICHAOUCH, Y. D., Torikachvili, M. S., Sun, J. Z., Geballe, T. H. 1987; 36 (16): 8414-8428

  View details for Web of Science ID A1987L403500030

• A PHOTOEMISSION-STUDY OF THE SI(111)/GD INTERFACE - A COMPARISON WITH THE BULK SILICIDES JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B Puppin, E., Nogami, J., Carbone, C., Shen, Z. X., LINDAU, I., Pate, B. B., ABBATI, I., Braicovich, L. 1987; 5 (4): 1083-1086

  View details for Web of Science ID A1987J673000049

• PHOTOEMISSION STUDY OF THE ELECTRONIC STRUCTURE of COPPER OXIDE SUPERCONDUCTORS MRS Online, Volume 99 (Symposium AA – High-Temperature Superconductors)1 Shen, Z., Allen, J., Yeh, J., Kang, J., Ellis, W., Spicer, W., Lindau, I., Sun, J., Geballe, T., Maple, M., Dalichaouch, Y., Torikachvei, M. 1987