Jonathan Sobota

All Publications

• 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

• Reversal of spin-polarization near the Fermi level of the Rashba semiconductor BiTeCl NPJ QUANTUM MATERIALS Qu, J., Han, X., Sakamoto, S., Jia, C. J., Liu, J., Li, H., Guan, D., Zeng, Y., Schuler, M., Kirchmann, P. S., Moritz, B., Hussain, Z., Devereaux, T. P., Shen, Z., Sobota, J. A. 2023; 8 (1)

  View details for DOI 10.1038/s41535-023-00546-x

  View details for Web of Science ID 000941936700001

• 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

• Probing topological phase transitions using high-harmonic generation NATURE PHOTONICS Heide, C., Kobayashi, Y., Baykusheva, D. R., Jain, D., Sobota, J. A., Hashimoto, M., Kirchmann, P. S., Oh, S., Heinz, T. F., Reis, D. A., Ghimire, S. 2022

  View details for DOI 10.1038/s41566-022-01050-7

  View details for Web of Science ID 000841689800001

• Connection between coherent phonons and electron-phonon coupling in Sb (111) PHYSICAL REVIEW B Sakamoto, S., Gauthier, N., Kirchmann, P. S., Sobota, J. A., Shen, Z. 2022; 105 (16)

  View details for DOI 10.1103/PhysRevB.105.L161107

  View details for Web of Science ID 000806812400002

• 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

• All-Optical Probe of Three-Dimensional Topological Insulators Based on High-Harmonic Generation by Circularly Polarized Laser Fields. Nano letters Baykusheva, D., Chacon, A., Lu, J., Bailey, T. P., Sobota, J. A., Soifer, H., Kirchmann, P. S., Rotundu, C., Uher, C., Heinz, T. F., Reis, D. A., Ghimire, S. 2021

  Abstract

  We report the observation of an anomalous nonlinear optical response of the prototypical three-dimensional topological insulator bismuth selenide through the process of high-order harmonic generation. We find that the generation efficiency increases as the laser polarization is changed from linear to elliptical, and it becomes maximum for circular polarization. With the aid of a microscopic theory and a detailed analysis of the measured spectra, we reveal that such anomalous enhancement encodes the characteristic topology of the band structure that originates from the interplay of strong spin-orbit coupling and time-reversal symmetry protection. The implications are in ultrafast probing of topological phase transitions, light-field driven dissipationless electronics, and quantum computation.

  View details for DOI 10.1021/acs.nanolett.1c02145

  View details for PubMedID 34676752

• 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

• 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

• 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

• High-Harmonic Generation from Topological Insulators Baykusheva, D., Lu, J., Sobota, J. A., Soifer, H., Rotundu, C. R., Kirchmann, P. S., Reis, D. A., Ghimire, S., IEEE IEEE. 2019

  View details for Web of Science ID 000482226301135

• 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

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

  View details for PubMedID 28959972

• 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

• 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

• 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)

  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

• 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

• 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)

  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

• 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

• 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 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

• 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

• 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

• RKKY interactions in the regime of strong localization PHYSICAL REVIEW B Sobota, J. A., Tanaskovic, D., Dobrosavljevic, V. 2007; 76 (24)

  View details for DOI 10.1103/PhysRevB.76.245106

  View details for Web of Science ID 000251986600022