David Goldhaber-Gordon

All Publications

• Quantitative determination of twist angle and strain in Van der Waals moiré superlattices APPLIED PHYSICS LETTERS Tran, S. J., Uslu, J., Pendharkar, M., Finney, J., Sharpe, A. L., Hocking, M., Bittner, N. J., Watanabe, K., Taniguchi, T., Kastner, M. A., Mannix, A. J., Goldhaber-Gordon, D. 2024; 125 (11)

  View details for DOI 10.1063/5.0223777

  View details for Web of Science ID 001313187100002

• Chemically Tailored Growth of 2D Semiconductors via Hybrid Metal-Organic Chemical Vapor Deposition. ACS nano Zhang, Z., Hoang, L., Hocking, M., Peng, Z., Hu, J., Zaborski, G., Reddy, P. D., Dollard, J., Goldhaber-Gordon, D., Heinz, T. F., Pop, E., Mannix, A. J. 2024

  Abstract

  Two-dimensional (2D) semiconducting transition-metal dichalcogenides (TMDCs) are an exciting platform for excitonic physics and next-generation electronics, creating a strong demand to understand their growth, doping, and heterostructures. Despite significant progress in solid-source (SS-) and metal-organic chemical vapor deposition (MOCVD), further optimization is necessary to grow highly crystalline 2D TMDCs with controlled doping. Here, we report a hybrid MOCVD growth method that combines liquid-phase metal precursor deposition and vapor-phase organo-chalcogen delivery to leverage the advantages of both MOCVD and SS-CVD. Using our hybrid approach, we demonstrate WS2 growth with tunable morphologies─from separated single-crystal domains to continuous monolayer films─on a variety of substrates, including sapphire, SiO2, and Au. These WS2 films exhibit narrow neutral exciton photoluminescence line widths down to 27-28 meV and room-temperature mobility up to 34-36 cm2 V-1 s-1. Through simple modifications to the liquid precursor composition, we demonstrate the growth of V-doped WS2, MoxW1-xS2 alloys, and in-plane WS2-MoS2 heterostructures. This work presents an efficient approach for addressing a variety of TMDC synthesis needs on a laboratory scale.

  View details for DOI 10.1021/acsnano.4c02164

  View details for PubMedID 39230253

• Fractional AC Josephson effect in a topological insulator proximitized by a self-formed superconductor PHYSICAL REVIEW B Rosen, I. T., Trimble, C. J., Andersen, M. P., Mikheev, E., Li, Y., Liu, Y., Tai, L., Zhang, P., Wang, K. L., Cui, Y., Kastner, M. A., Williams, J. R., Goldhaber-Gordon, D. 2024; 110 (6)

  View details for DOI 10.1103/PhysRevB.110.064511

  View details for Web of Science ID 001296359500003

• Thermal relaxation of strain and twist in ferroelectric hexagonal boron nitride moiré interfaces JOURNAL OF APPLIED PHYSICS Hocking, M., Henzinger, C. E., Tran, S. J., Pendharkar, M., Bittner, N. J., Watanabe, K., Taniguchi, T., Goldhaber-Gordon, D., Mannix, A. J. 2024; 136 (2)

  View details for DOI 10.1063/5.0210112

  View details for Web of Science ID 001272420800003

• Torsional force microscopy of van der Waals moirés and atomic lattices. Proceedings of the National Academy of Sciences of the United States of America Pendharkar, M., Tran, S. J., Zaborski, G., Finney, J., Sharpe, A. L., Kamat, R. V., Kalantre, S. S., Hocking, M., Bittner, N. J., Watanabe, K., Taniguchi, T., Pittenger, B., Newcomb, C. J., Kastner, M. A., Mannix, A. J., Goldhaber-Gordon, D. 2024; 121 (10): e2314083121

  Abstract

  In a stack of atomically thin van der Waals layers, introducing interlayer twist creates a moiré superlattice whose period is a function of twist angle. Changes in that twist angle of even hundredths of a degree can dramatically transform the system's electronic properties. Setting a precise and uniform twist angle for a stack remains difficult; hence, determining that twist angle and mapping its spatial variation is very important. Techniques have emerged to do this by imaging the moiré, but most of these require sophisticated infrastructure, time-consuming sample preparation beyond stack synthesis, or both. In this work, we show that torsional force microscopy (TFM), a scanning probe technique sensitive to dynamic friction, can reveal surface and shallow subsurface structure of van der Waals stacks on multiple length scales: the moirés formed between bi-layers of graphene and between graphene and hexagonal boron nitride (hBN) and also the atomic crystal lattices of graphene and hBN. In TFM, torsional motion of an Atomic Force Microscope (AFM) cantilever is monitored as it is actively driven at a torsional resonance while a feedback loop maintains contact at a set force with the sample surface. TFM works at room temperature in air, with no need for an electrical bias between the tip and the sample, making it applicable to a wide array of samples. It should enable determination of precise structural information including twist angles and strain in moiré superlattices and crystallographic orientation of van der Waals flakes to support predictable moiré heterostructure fabrication.

  View details for DOI 10.1073/pnas.2314083121

  View details for PubMedID 38427599

• Universal Conductance Fluctuations in a MnBi2Te4 Thin Film. Nano letters Andersen, M. P., Mikheev, E., Rosen, I. T., Tai, L., Zhang, P., Wang, K. L., Kastner, M. A., Goldhaber-Gordon, D. 2023

  Abstract

  Quantum coherence of electrons can produce striking behaviors in mesoscopic conductors. Although magnetic order can also strongly affect transport, the combination of coherence and magnetic order has been largely unexplored. Here, we examine quantum coherence-driven universal conductance fluctuations in the antiferromagnetic, canted antiferromagnetic, and ferromagnetic phases of a thin film of the topological material MnBi2Te4. In each magnetic phase, we extract a charge carrier phase coherence length of about 100 nm. The conductance magnetofingerprint is repeatable when sweeping applied magnetic field within one magnetic phase. Surprisingly, in the antiferromagnetic and canted antiferromagnetic phases, but not in the ferromagnetic phase, the magnetofingerprint depends on the direction of the field sweep. To explain our observations, we suggest that conductance fluctuation measurements are sensitive to the motion and nucleation of magnetic domain walls in MnBi2Te4.

  View details for DOI 10.1021/acs.nanolett.3c02932

  View details for PubMedID 38029283

• Unusual magnetotransport in twisted bilayer graphene from strain-induced open Fermi surfaces. Proceedings of the National Academy of Sciences of the United States of America Wang, X., Finney, J., Sharpe, A. L., Rodenbach, L. K., Hsueh, C. L., Watanabe, K., Taniguchi, T., Kastner, M. A., Vafek, O., Goldhaber-Gordon, D. 2023; 120 (34): e2307151120

  Abstract

  Anisotropic hopping in a toy Hofstadter model was recently invoked to explain a rich and surprising Landau spectrum measured in twisted bilayer graphene away from the magic angle. Suspecting that such anisotropy could arise from unintended uniaxial strain, we extend the Bistritzer-MacDonald model to include uniaxial heterostrain and present a detailed analysis of its impact on band structure and magnetotransport. We find that such strain strongly influences band structure, shifting the three otherwise-degenerate van Hove points to different energies. Coupled to a Boltzmann magnetotransport calculation, this reproduces previously unexplained nonsaturating [Formula: see text] magnetoresistance over broad ranges of density near filling [Formula: see text] and predicts subtler features that had not been noticed in the experimental data. In contrast to these distinctive signatures in longitudinal resistivity, the Hall coefficient is barely influenced by strain, to the extent that it still shows a single sign change on each side of the charge neutrality point-surprisingly, this sign change no longer occurs at a van Hove point. The theory also predicts a marked rotation of the electrical transport principal axes as a function of filling even for fixed strain and for rigid bands. More careful examination of interaction-induced nematic order versus strain effects in twisted bilayer graphene could thus be in order.

  View details for DOI 10.1073/pnas.2307151120

  View details for PubMedID 37579169

• Magnetic Field-Stabilized Wigner Crystal States in a Graphene Moiré Superlattice. Nano letters Chen, G., Zhang, Y. H., Sharpe, A., Zhang, Z., Wang, S., Jiang, L., Lyu, B., Li, H., Watanabe, K., Taniguchi, T., Shi, Z., Goldhaber-Gordon, D., Zhang, Y., Wang, F. 2023

  Abstract

  ABC-stacked trilayer graphene on boron nitride (ABC-TLG/hBN) moiré superlattices provides a tunable platform for exploring Wigner crystal states in which the electron correlation can be controlled by electric and magnetic fields. Here we report the observation of magnetic field-stabilized Wigner crystal states in a ABC-TLG/hBN. We show that correlated insulating states emerge at multiple fractional and integer fillings corresponding to ν = 1/3, 2/3, 1, 4/3, 5/3, and 2 electrons per moiré lattice site under a magnetic field. These correlated insulating states can be attributed to generalized Mott states for the integer fillings and generalized Wigner crystal states for the fractional fillings. The generalized Wigner crystal states are stabilized by a vertical magnetic field and are strongest at one magnetic flux quantum per three moiré superlattices. The ν = 2 insulating state persists up to 30 T, which can be described by a Mott-Hofstadter transition at a high magnetic field.

  View details for DOI 10.1021/acs.nanolett.3c01741

  View details for PubMedID 37474137

• Low-damage electron beam lithography for nanostructures on Bi2Se3-class topological insulator thin films JOURNAL OF APPLIED PHYSICS Andersen, M. P., Rodenbach, L. K., Rosen, I. T., Lin, S. C., Pan, L., Zhang, P., Tai, L., Wang, K. L., Kastner, M. A., Goldhaber-Gordon, D. 2023; 133 (24)

  View details for DOI 10.1063/5.0144726

  View details for Web of Science ID 001031342700006

• A clean ballistic quantum point contact in strontium titanate NATURE ELECTRONICS Mikheev, E., Rosen, I. T., Kombe, J., Damanet, F., Kastner, M. A., Goldhaber-Gordon, D. 2023

  View details for DOI 10.1038/s41928-023-00981-5

  View details for Web of Science ID 001014527900001

• Probing single electron scattering through a non-Fermi-liquid charge-Kondo device PHYSICAL REVIEW B Sela, E., Goldhaber-Gordon, D., Anthore, A., Pierre, F., Oreg, Y. 2023; 107 (16)

  View details for DOI 10.1103/PhysRevB.107.L161108

  View details for Web of Science ID 001024463300004

• Z_{3} Parafermion in the Double Charge Kondo Model. Physical review letters Karki, D. B., Boulat, E., Pouse, W., Goldhaber-Gordon, D., Mitchell, A. K., Mora, C. 2023; 130 (14): 146201

  Abstract

  Quantum impurity models with frustrated Kondo interactions can support quantum critical points with fractionalized excitations. Recent experiments [W. Pouse et al., Nat. Phys. (2023)NPAHAX1745-247310.1038/s41567-022-01905-4] on a circuit containing two coupled metal-semiconductor islands exhibit transport signatures of such a critical point. Here, we show using bosonization that the double charge-Kondo model describing the device can be mapped in the Toulouse limit to a sine-Gordon model. Its Bethe-ansatz solution shows that a Z_{3} parafermion emerges at the critical point, characterized by a fractional 1/2ln(3) residual entropy, and scattering fractional charges e/3. We also present full numerical renormalization group calculations for the model and show that the predicted behavior of conductance is consistent with experimental results.

  View details for DOI 10.1103/PhysRevLett.130.146201

  View details for PubMedID 37084428

• Visualizing the atomic-scale origin of metallic behavior in Kondo insulators. Science (New York, N.Y.) Pirie, H., Mascot, E., Matt, C. E., Liu, Y., Chen, P., Hamidian, M. H., Saha, S., Wang, X., Paglione, J., Luke, G., Goldhaber-Gordon, D., Hirjibehedin, C. F., Davis, J. C., Morr, D. K., Hoffman, J. E. 2023; 379 (6638): 1214-1218

  Abstract

  A Kondo lattice is often electrically insulating at low temperatures. However, several recent experiments have detected signatures of bulk metallicity within this Kondo insulating phase. In this study, we visualized the real-space charge landscape within a Kondo lattice with atomic resolution using a scanning tunneling microscope. We discovered nanometer-scale puddles of metallic conduction electrons centered around uranium-site substitutions in the heavy-fermion compound uranium ruthenium silicide (URu2Si2) and around samarium-site defects in the topological Kondo insulator samarium hexaboride (SmB6). These defects disturbed the Kondo screening cloud, leaving behind a fingerprint of the metallic parent state. Our results suggest that the three-dimensional quantum oscillations measured in SmB6 arise from Kondo-lattice defects, although we cannot exclude other explanations. Our imaging technique could enable the development of atomic-scale charge sensors using heavy-fermion probes.

  View details for DOI 10.1126/science.abq5375

  View details for PubMedID 36952423

• Quantum simulation of an exotic quantum critical point in a two-site charge Kondo circuit NATURE PHYSICS Pouse, W., Peeters, L., Hsueh, C. L., Gennser, U., Cavanna, A., Kastner, M. A., Mitchell, A. K., Goldhaber-Gordon, D. 2023

  View details for DOI 10.1038/s41567-022-01905-4

  View details for Web of Science ID 000950225400005

• Feedback lock-in: A versatile multi-terminal measurement system for electrical transport devices. The Review of scientific instruments Barnard, A. W., Mikheev, E., Finney, J., Hiller, H. S., Goldhaber-Gordon, D. 2023; 94 (1): 013902

  Abstract

  We present the design and implementation of a measurement system that enables parallel drive and detection of small currents and voltages at numerous electrical contacts to a multi-terminal electrical device. This system, which we term a feedback lock-in, combines digital control-loop feedback with software-defined lock-in measurements to dynamically source currents and measure small, pre-amplified potentials. The effective input impedance of each current/voltage probe can be set via software, permitting any given contact to behave as an open-circuit voltage lead or as a virtually grounded current source/sink. This enables programmatic switching of measurement configurations and permits measurement of currents at multiple drain contacts without the use of current preamplifiers. Our 32-channel implementation relies on commercially available digital input/output boards, home-built voltage preamplifiers, and custom open-source software. With our feedback lock-in, we demonstrate differential measurement sensitivity comparable to a widely used commercially available lock-in amplifier and perform efficient multi-terminal electrical transport measurements on twisted bilayer graphene and SrTiO3 quantum point contacts. The feedback lock-in also enables a new style of measurement using multiple current probes, which we demonstrate on a ballistic graphene device.

  View details for DOI 10.1063/5.0089194

  View details for PubMedID 36725603

• Feedback lock-in: A versatile multi-terminal measurement system for electrical transport devices REVIEW OF SCIENTIFIC INSTRUMENTS Barnard, A. W., Mikheev, E., Finney, J., Hiller, H. S., Goldhaber-Gordon, D. 2023; 94 (1)

  View details for DOI 10.1063/5.0089194

  View details for Web of Science ID 000907671000007

• Measured Potential Profile in a Quantum Anomalous Hall System Suggests Bulk-Dominated Current Flow. Physical review letters Rosen, I. T., Andersen, M. P., Rodenbach, L. K., Tai, L., Zhang, P., Wang, K. L., Kastner, M. A., Goldhaber-Gordon, D. 2022; 129 (24): 246602

  Abstract

  Ideally, quantum anomalous Hall systems should display zero longitudinal resistance. Yet in experimental quantum anomalous Hall systems elevated temperature can make the longitudinal resistance finite, indicating dissipative flow of electrons. Here, we show that the measured potentials at multiple locations within a device at elevated temperature are well described by solution of Laplace's equation, assuming spatially uniform conductivity, suggesting nonequilibrium current flows through the two-dimensional bulk. Extrapolation suggests that at even lower temperatures current may still flow primarily through the bulk rather than, as had been assumed, through edge modes. An argument for bulk current flow previously applied to quantum Hall systems supports this picture.

  View details for DOI 10.1103/PhysRevLett.129.246602

  View details for PubMedID 36563259

• Metrological Assessment of Quantum Anomalous Hall Properties PHYSICAL REVIEW APPLIED Rodenbach, L. K., Panna, A. R., Payagala, S. U., Rosen, I. T., Andersen, M. P., Zhang, P., Tai, L., Wang, K. L., Jarrett, D. G., Elmquist, R. E., Newell, D. B., Goldhaber-Gordon, D., Rigosi, A. F. 2022; 18 (3)

  View details for DOI 10.1103/PhysRevApplied.18.034008

  View details for Web of Science ID 000852221100002

• Ionic Liquid Gating of SrTiO3 Lamellas Fabricated with a Focused Ion Beam. Nano letters Mikheev, E., Zimmerling, T., Estry, A., Moll, P. J., Goldhaber-Gordon, D. 2022

  Abstract

  In this work, we combine two previously incompatible techniques for defining electronic devices: shaping three-dimensional crystals by focused ion beam (FIB), and two-dimensional electrostatic accumulation of charge carriers. The principal challenge for this integration is nanometer-scale surface damage inherent to any FIB-based fabrication. We address this by using a sacrificial protective layer to preserve a selected pristine surface. The test case presented here is accumulation of 2D carriers by ionic liquid gating at the surface of a micron-scale SrTiO3 lamella. Preservation of surface quality is reflected in superconductivity of the accumulated carriers. This technique opens new avenues for realizing electrostatic charge tuning in materials that are not available as large or exfoliatable single crystals, and for patterning the geometry of the accumulated carriers.

  View details for DOI 10.1021/acs.nanolett.1c04447

  View details for PubMedID 35576585

• Nanoscale Electronic Transparency of Wafer-Scale Hexagonal Boron Nitride. Nano letters Zerger, C. Z., Rodenbach, L. K., Chen, Y., Safvati, B., Brubaker, M. Z., Tran, S., Chen, T., Li, M., Li, L., Goldhaber-Gordon, D., Manoharan, H. C. 2022

  Abstract

  Monolayer hexagonal boron nitride (hBN) has attracted interest as an ultrathin tunnel barrier or environmental protection layer. Recently, wafer-scale hBN growth on Cu(111) was developed for semiconductor chip applications. For basic research and technology, understanding how hBN perturbs underlying electronically active layers is critical. Encouragingly, hBN/Cu(111) has been shown to preserve the Cu(111) surface state (SS), but it was unknown how tunneling into this SS through hBN varies spatially. Here, we demonstrate that the Cu(111) SS under wafer-scale hBN is homogeneous in energy and spectral weight over nanometer length scales and across atomic terraces. In contrast, a new spectral feature─not seen on bare Cu(111)─varies with atomic registry and shares the spatial periodicity of the hBN/Cu(111) moire. This work demonstrates that, for some 2D electron systems, an hBN overlayer can act as a protective yet remarkably transparent window on fragile low-energy electronic structure below.

  View details for DOI 10.1021/acs.nanolett.1c04274

  View details for PubMedID 35536749

• Directional ballistic transport in the two-dimensional metal PdCoO2. Nature physics Bachmann, M. D., Sharpe, A. L., Baker, G., Barnard, A. W., Putzke, C., Scaffidi, T., Nandi, N., McGuinness, P. H., Zhakina, E., Moravec, M., Khim, S., König, M., Goldhaber-Gordon, D., Bonn, D. A., Mackenzie, A. P., Moll, P. J. 2022; 18 (7): 819-824

  Abstract

  In an idealized infinite crystal, the material properties are constrained by the symmetries of the unit cell. The point-group symmetry is broken by the sample shape of any finite crystal, but this is commonly unobservable in macroscopic metals. To sense the shape-induced symmetry lowering in such metals, long-lived bulk states originating from an anisotropic Fermi surface are needed. Here we show how a strongly facetted Fermi surface and the long quasiparticle mean free path present in microstructures of PdCoO2 yield an in-plane resistivity anisotropy that is forbidden by symmetry on an infinite hexagonal lattice. We fabricate bar-shaped transport devices narrower than the mean free path from single crystals using focused ion beam milling, such that the ballistic charge carriers at low temperatures frequently collide with both of the side walls that define the channel. Two symmetry-forbidden transport signatures appear: the in-plane resistivity anisotropy exceeds a factor of 2, and a transverse voltage appears in zero magnetic field. Using ballistic Monte Carlo simulations and a numerical solution of the Boltzmann equation, we identify the orientation of the narrow channel as the source of symmetry breaking.

  View details for DOI 10.1038/s41567-022-01570-7

  View details for PubMedID 35847475

  View details for PubMedCentralID PMC9279146

• Directional ballistic transport in the two-dimensional metal PdCoO2 NATURE PHYSICS Bachmann, M. D., Sharpe, A. L., Baker, G., Barnard, A. W., Putzke, C., Scaffidi, T., Nandi, N., McGuinness, P. H., Zhakina, E., Moravec, M., Khim, S., Konig, M., Goldhaber-Gordon, D., Bonn, D. A., Mackenzie, A. P., Moll, P. W. 2022

  View details for DOI 10.1038/s41567-022-01570-7

  View details for Web of Science ID 000792553700001

• Clean quantum point contacts in an InAs quantum well grown on a lattice-mismatched InP substrate PHYSICAL REVIEW B Hsueh, C. L., Sriram, P., Wang, T., Thomas, C., Gardner, G., Kastner, M. A., Manfra, M. J., Goldhaber-Gordon, D. 2022; 105 (19)

  View details for DOI 10.1103/PhysRevB.105.195303

  View details for Web of Science ID 000804737800007

• Unusual magnetotransport in twisted bilayer graphene. Proceedings of the National Academy of Sciences of the United States of America Finney, J., Sharpe, A. L., Fox, E. J., Hsueh, C. L., Parker, D. E., Yankowitz, M., Chen, S., Watanabe, K., Taniguchi, T., Dean, C. R., Vishwanath, A., Kastner, M. A., Goldhaber-Gordon, D. 2022; 119 (16): e2118482119

  Abstract

  SignificanceWhen two sheets of graphene are twisted to the magic angle of 1.1∘, the resulting flat moiré bands can host exotic correlated electronic states such as superconductivity and ferromagnetism. Here, we show transport properties of a twisted bilayer graphene device at 1.38∘, far enough above the magic angle that we do not expect exotic correlated states. Instead, we see several unusual behaviors in the device's resistivity upon tuning both charge carrier density and perpendicular magnetic field. We can reproduce these behaviors with a surprisingly simple model based on Hofstadter's butterfly. These results shed light on the underlying properties of twisted bilayer graphene.

  View details for DOI 10.1073/pnas.2118482119

  View details for PubMedID 35412918

• Tunable Orbital Ferromagnetism at Noninteger Filling of a Moire Superlattice. Nano letters Chen, G., Sharpe, A. L., Fox, E. J., Wang, S., Lyu, B., Jiang, L., Li, H., Watanabe, K., Taniguchi, T., Crommie, M. F., Kastner, M. A., Shi, Z., Goldhaber-Gordon, D., Zhang, Y., Wang, F. 1800

  Abstract

  The flat bands resulting from moire superlattices exhibit fascinating correlated electron phenomena such as correlated insulators, ( Nature 2018, 556 (7699), 80-84), ( Nature Physics 2019, 15 (3), 237) superconductivity, ( Nature 2018, 556 (7699), 43-50), ( Nature 2019, 572 (7768), 215-219) and orbital magnetism. ( Science 2019, 365 (6453), 605-608), ( Nature 2020, 579 (7797), 56-61), ( Science 2020, 367 (6480), 900-903) Such magnetism has been observed only at particular integer multiples of n0, the density corresponding to one electron per moire superlattice unit cell. Here, we report the experimental observation of ferromagnetism at noninteger filling (NIF) of a flat Chern band in a ABC-TLG/hBN moire superlattice. This state exhibits prominent ferromagnetic hysteresis behavior with large anomalous Hall resistivity in a broad region of densities centered in the valence miniband at n = -2.3n0. We observe that, not only the magnitude of the anomalous Hall signal, but also the sign of the hysteretic ferromagnetic response can be modulated by tuning the carrier density and displacement field. Rotating the sample in a fixed magnetic field demonstrates that the ferromagnetism is highly anisotropic and likely purely orbital in character.

  View details for DOI 10.1021/acs.nanolett.1c03699

  View details for PubMedID 34978444

• Application-driven synthesis and characterization of hexagonal boron nitride deposited on metals and carbon nanotubes 2D MATERIALS Chen, V., Shin, Y., Mikheev, E., Lin, Q., Martis, J., Zhang, Z., Chatterjee, S., Majumdar, A., Wong, H., Goldhaber-Gordon, D., Pop, E. 2021; 8 (4)

  View details for DOI 10.1088/2053-1583/ac10f1

  View details for Web of Science ID 000696373700001

• Quantized critical supercurrent in SrTiO3-based quantum point contacts. Science advances Mikheev, E., Rosen, I. T., Goldhaber-Gordon, D. 2021; 7 (40): eabi6520

  Abstract

  [Figure: see text].

  View details for DOI 10.1126/sciadv.abi6520

  View details for PubMedID 34597141

• Evidence of Orbital Ferromagnetism in Twisted Bilayer Graphene Aligned to Hexagonal Boron Nitride. Nano letters Sharpe, A. L., Fox, E. J., Barnard, A. W., Finney, J., Watanabe, K., Taniguchi, T., Kastner, M. A., Goldhaber-Gordon, D. 2021

  Abstract

  We have previously reported ferromagnetism evinced by a large hysteretic anomalous Hall effect in twisted bilayer graphene (tBLG). Subsequent measurements of a quantized Hall resistance and small longitudinal resistance confirmed that this magnetic state is a Chern insulator. Here, we report that when tilting the sample in an external magnetic field, the ferromagnetism is highly anisotropic. Because spin-orbit coupling is weak in graphene, such anisotropy is unlikely to come from spin but rather favors theories in which the ferromagnetism is orbital. We know of no other case in which ferromagnetism has a purely orbital origin. For an applied in-plane field larger than 5 T, the out-of-plane magnetization is destroyed, suggesting a transition to a new phase.

  View details for DOI 10.1021/acs.nanolett.1c00696

  View details for PubMedID 33970644

• Tunable correlated Chern insulator and ferromagnetism in a moire superlattice (vol 579, pg 56, 2020) NATURE Chen, G., Sharpe, A. L., Fox, E. J., Zhang, Y., Wang, S., Jiang, L., Lyu, B., Li, H., Watanabe, K., Taniguchi, T., Shi, Z., Senthil, T., Goldhaber-Gordon, D., Zhang, Y., Wang, F. 2020: E3

  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/s41586-020-2237-5

  View details for Web of Science ID 000529132400001

  View details for PubMedID 32404999

• Giant orbital magnetoelectric effect and current-induced magnetization switching in twisted bilayer graphene. Nature communications He, W. Y., Goldhaber-Gordon, D. n., Law, K. T. 2020; 11 (1): 1650

  Abstract

  Recently, quantum anomalous Hall effect with spontaneous ferromagnetism was observed in twisted bilayer graphenes (TBG) near 3/4 filling. Importantly, it was observed that an extremely small current can switch the direction of the magnetization. This offers the prospect of realizing low energy dissipation magnetic memories. However, the mechanism of the current-driven magnetization switching is poorly understood as the charge currents in graphenes are generally believed to be non-magnetic. In this work, we demonstrate that in TBG, the twisting and substrate induced symmetry breaking allow an out of plane orbital magnetization to be generated by a charge current. Moreover, the large Berry curvatures of the flat bands give the Bloch electrons large orbital magnetic moments so that a small current can generate a large orbital magnetization. We further demonstrate how the charge current can switch the magnetization of the ferromagnetic TBG near 3/4 filling as observed in the experiments.

  View details for DOI 10.1038/s41467-020-15473-9

  View details for PubMedID 32246024

• Super-geometric electron focusing on the hexagonal Fermi surface of PdCoO2. Nature communications Bachmann, M. D., Sharpe, A. L., Barnard, A. W., Putzke, C., Konig, M., Khim, S., Goldhaber-Gordon, D., Mackenzie, A. P., Moll, P. J. 2019; 10 (1): 5081

  Abstract

  Geometric electron optics may be implemented in solids when electron transport is ballistic on the length scale of a device. Currently, this is realized mainly in 2D materials characterized by circular Fermi surfaces. Here we demonstrate that the nearly perfectly hexagonal Fermi surface of PdCoO2 gives rise to highly directional ballistic transport. We probe this directional ballistic regime in a single crystal of PdCoO2 by use of focused ion beam (FIB) micro-machining, defining crystalline ballistic circuits with features as small as 250nm. The peculiar hexagonal Fermi surface naturally leads to enhanced electron self-focusing effects in a magnetic field compared to circular Fermi surfaces. This super-geometric focusing can be quantitatively predicted for arbitrary device geometry, based on the hexagonal cyclotron orbits appearing in this material. These results suggest a novel class of ballistic electronic devices exploiting the unique transport characteristics of strongly faceted Fermi surfaces.

  View details for DOI 10.1038/s41467-019-13020-9

  View details for PubMedID 31705049

• Signatures of tunable superconductivity in a trilayer graphene moire superlattice. Nature Chen, G., Sharpe, A. L., Gallagher, P., Rosen, I. T., Fox, E. J., Jiang, L., Lyu, B., Li, H., Watanabe, K., Taniguchi, T., Jung, J., Shi, Z., Goldhaber-Gordon, D., Zhang, Y., Wang, F. 2019

  Abstract

  Understanding the mechanism of high-transition-temperature (high-Tc) superconductivity is a central problem in condensed matter physics. It is often speculated that high-Tc superconductivity arises in a doped Mott insulator1 as described by the Hubbard model2-4. An exact solution of the Hubbard model, however, is extremely challenging owing to the strong electron-electron correlation in Mott insulators. Therefore, it is highly desirable to study a tunable Hubbard system, in which systematic investigations of the unconventional superconductivity and its evolution with the Hubbard parameters can deepen our understanding of the Hubbard model. Here we report signatures of tunable superconductivity in an ABC-trilayer graphene (TLG) and hexagonal boron nitride (hBN) moire superlattice. Unlike in 'magic angle' twisted bilayer graphene, theoretical calculations show that under a vertical displacement field, the ABC-TLG/hBN heterostructure features an isolated flat valence miniband associated with a Hubbard model on a triangular superlattice5,6 where the bandwidth can be tuned continuously with the vertical displacement field. Upon applying such a displacement field we find experimentally that the ABC-TLG/hBN superlattice displays Mott insulating states below 20 kelvin at one-quarter and one-half fillings of the states, corresponding to one and two holes per unit cell, respectively. Upon further cooling, signatures of superconductivity ('domes') emerge below 1 kelvin for the electron- and hole-doped sides of the one-quarter-filling Mott state. The electronic behaviour in the ABC-TLG/hBN superlattice is expected to depend sensitively on the interplay between the electron-electron interaction and the miniband bandwidth. By varying the vertical displacement field, we demonstrate transitions from the candidate superconductor to Mott insulator and metallic phases. Our study shows that ABC-TLG/hBN heterostructures offer attractive model systems in which to explore rich correlated behaviour emerging in the tunable triangular Hubbard model.

  View details for DOI 10.1038/s41586-019-1393-y

  View details for PubMedID 31316203

• 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

• Quantum-Hall to Insulator Transition in Ultra-Low-Carrier-Density Topological Insulator Films and a Hidden Phase of the Zeroth Landau Level. Advanced materials (Deerfield Beach, Fla.) Salehi, M., Shapourian, H., Rosen, I. T., Han, M., Moon, J., Shibayev, P., Jain, D., Goldhaber-Gordon, D., Oh, S. 2019: e1901091

  Abstract

  A key feature of the topological surface state under a magnetic field is the presence of the zeroth Landau level at the zero energy. Nonetheless, it is challenging to probe the zeroth Landau level due to large electron-hole puddles smearing its energy landscape. Here, by developing ultra-low-carrier density topological insulator Sb2 Te3 films, an extreme quantum limit of the topological surface state is reached and a hidden phase at the zeroth Landau level is uncovered. First, an unexpected quantum-Hall-to-insulator-transition near the zeroth Landau level is discovered. Then, through a detailed scaling analysis, it is found that this quantum-Hall-to-insulator-transition belongs to a new universality class, implying that the insulating phase discovered here has a fundamentally different origin from those in nontopological systems.

  View details for DOI 10.1002/adma.201901091

  View details for PubMedID 31259439

• Significant Phonon Drag Enables High Power Factor in the AlGaN/GaN Two-Dimensional Electron Gas. Nano letters Yalamarthy, A. S., Munoz Rojo, M., Bruefach, A., Boone, D., Dowling, K. M., Satterthwaite, P. F., Goldhaber-Gordon, D., Pop, E., Senesky, D. G. 2019

  Abstract

  In typical thermoelectric energy harvesters and sensors, the Seebeck effect is caused by diffusion of electrons or holes in a temperature gradient. However, the Seebeck effect can also have a phonon drag component, due to momentum exchange between charge carriers and lattice phonons, which is more difficult to quantify. Here, we present the first study of phonon drag in the AlGaN/GaN two-dimensional electron gas (2DEG). We find that phonon drag does not contribute significantly to the thermoelectric behavior of devices with 100 nm GaN thickness, which suppresses the phonon mean free path. However, when the thickness is increased to 1.2 mum, up to 32% (88%) of the Seebeck coefficient at 300 K (50 K) can be attributed to the drag component. In turn, the phonon drag enables state-of-the-art thermoelectric power factor in the thicker GaN film, up to 40 mW m-1 K-2 at 50 K. By measuring the thermal conductivity of these AlGaN/GaN films, we show that the magnitude of the phonon drag can increase even when the thermal conductivity decreases. Decoupling of thermal conductivity and Seebeck coefficient could enable important advancements in thermoelectric power conversion with devices based on 2DEGs.

  View details for DOI 10.1021/acs.nanolett.9b00901

  View details for PubMedID 31088057

• Absence of strong localization at low conductivity in the topological surface state of low-disorder Sb2Te3 PHYSICAL REVIEW B Rosen, I. T., Yudhistira, I., Sharma, G., Salehi, M., Kastner, M. A., Oh, S., Adam, S., Goldhaber-Gordon, D. 2019; 99 (20)

  View details for DOI 10.1103/PhysRevB.99.201101

  View details for Web of Science ID 000466609900001

• Emergent ferromagnetism near three-quarters filling in twisted bilayer graphene. Science (New York, N.Y.) Sharpe, A. L., Fox, E. J., Barnard, A. W., Finney, J. n., Watanabe, K. n., Taniguchi, T. n., Kastner, M. A., Goldhaber-Gordon, D. n. 2019

  Abstract

  When two sheets of graphene are stacked at a small twist angle, the resulting flat superlattice minibands are expected to strongly enhance electron-electron interactions. Here we present evidence that near three-quarters (3/4) filling of the conduction miniband these enhanced interactions drive the twisted bilayer graphene into a ferromagnetic state. In a narrow density range around an apparent insulating state at 3/4, we observe emergent ferromagnetic hysteresis, with a giant anomalous Hall (AH) effect as large as 10.4 kΩ and indications of chiral edge states. Surprisingly, the magnetization of the sample can be reversed by applying a small DC current. Although the AH resistance is not quantized and dissipation is significant, our measurements suggest that the system may be an incipient Chern insulator.

  View details for DOI 10.1126/science.aaw3780

  View details for PubMedID 31346139

• Optical Imaging and Spectroscopic Characterization of Self-Assembled Environmental Adsorbates on Graphene NANO LETTERS Gallagher, P., Li, Y., Watanabe, K., Taniguchi, T., Heinz, T. F., Goldhaber-Gordon, D. 2018; 18 (4): 2603–8

  Abstract

  Topographic studies using scanning probes have found that graphene surfaces are often covered by micron-scale domains of periodic stripes with a 4 nm pitch. These stripes have been variously interpreted as structural ripples or as self-assembled adsorbates. We show that the stripe domains are optically anisotropic by imaging them using a polarization-contrast technique. Optical spectra between 1.1 and 2.8 eV reveal that the anisotropy in the in-plane dielectric function is predominantly real, reaching 0.6 for an assumed layer thickness of 0.3 nm. The spectra are incompatible with a rippled graphene sheet but would be quantitatively explained by the self-assembly of chainlike organic molecules into nanoscale stripes.

  View details for DOI 10.1021/acs.nanolett.8b00348

  View details for Web of Science ID 000430155900057

  View details for PubMedID 29589951

• Using liquid electrolytes in dielectric reliability studies Lanza, M., Tang, K., Meng, A. C., Hui, F., Shi, Y., Han, T., Petach, T., Hitzman, C., Koh, A., Goldhaber-Gordon, D., McIntyre, P. C., IEEE IEEE. 2018

  View details for Web of Science ID 000444747600083

• Chiral transport along magnetic domain walls in the quantum anomalous Hall effect NPJ QUANTUM MATERIALS Rosen, I. T., Fox, E. J., Kou, X., Pan, L., Wang, K. L., Goldhaber-Gordon, D. 2017; 2

  View details for DOI 10.1038/s41535-017-0073-0

  View details for Web of Science ID 000423482500001

• Zero-field edge plasmons in a magnetic topological insulator NATURE COMMUNICATIONS Mahoney, A. C., Colless, J. I., Peeters, L., Pauka, S. J., Fox, E. J., Kou, X., Pan, L., Wang, K. L., Goldhaber-Gordon, D., Reilly, D. J. 2017; 8

  View details for DOI 10.1038/s41467-017-01984-5

  View details for Web of Science ID 000416399700009

• Zero-field edge plasmons in a magnetic topological insulator. Nature communications Mahoney, A. C., Colless, J. I., Peeters, L., Pauka, S. J., Fox, E. J., Kou, X., Pan, L., Wang, K. L., Goldhaber-Gordon, D., Reilly, D. J. 2017; 8 (1): 1836

  Abstract

  Incorporating ferromagnetic dopants into three-dimensional topological insulator thin films has recently led to the realisation of the quantum anomalous Hall effect. These materials are of great interest since they may support electrical currents that flow without resistance, even at zero magnetic field. To date, the quantum anomalous Hall effect has been investigated using low-frequency transport measurements. However, transport results can be difficult to interpret due to the presence of parallel conductive paths, or because additional non-chiral edge channels may exist. Here we move beyond transport measurements by probing the microwave response of a magnetised disk of Cr-(Bi,Sb)2Te3. We identify features associated with chiral edge plasmons, a signature that robust edge channels are intrinsic to this material system. Our results provide a measure of the velocity of edge excitations without contacting the sample, and pave the way for an on-chip circuit element of practical importance: the zero-field microwave circulator.

  View details for DOI 10.1038/s41467-017-01984-5

  View details for PubMedID 29184065

  View details for PubMedCentralID PMC5705665

• Disorder from the Bulk Ionic Liquid in Electric Double Layer Transistors. ACS nano Petach, T. A., Reich, K. V., Zhang, X., Watanabe, K., Taniguchi, T., Shklovskii, B. I., Goldhaber-Gordon, D. 2017; 11 (8): 8395-8400

  Abstract

  Ionic liquid gating has a number of advantages over solid-state gating, especially for flexible or transparent devices and for applications requiring high carrier densities. However, the large number of charged ions near the channel inevitably results in Coulomb scattering, which limits the carrier mobility in otherwise clean systems. We develop a model for this Coulomb scattering. We validate our model experimentally using ionic liquid gating of graphene across varying thicknesses of hexagonal boron nitride, demonstrating that disorder in the bulk ionic liquid often dominates the scattering.

  View details for DOI 10.1021/acsnano.7b03864

  View details for PubMedID 28753312

• Distinguishing Oxygen Vacancy Electromigration and Conductive Filament Formation in TiO2 Resistance Switching Using Liquid Electrolyte Contacts. Nano letters Tang, K., Meng, A. C., Hui, F., Shi, Y., Petach, T., Hitzman, C., Koh, A. L., Goldhaber-Gordon, D., Lanza, M., McIntyre, P. C. 2017; 17 (7): 4390-4399

  Abstract

  Resistance switching in TiO2 and many other transition metal oxide resistive random access memory materials is believed to involve the assembly and breaking of interacting oxygen vacancy filaments via the combined effects of field-driven ion migration and local electronic conduction leading to Joule heating. These complex processes are very difficult to study directly in part because the filaments form between metallic electrode layers that block their observation by most characterization techniques. By replacing the top electrode layer in a metal-insulator-metal memory structure with easily removable liquid electrolytes, either an ionic liquid (IL) with high resistance contact or a conductive aqueous electrolyte, we probe field-driven oxygen vacancy redistribution in TiO2 thin films under conditions that either suppress or promote Joule heating. Oxygen isotope exchange experiments indicate that exchange of oxygen ions between TiO2 and the IL is facile at room temperature. Oxygen loss significantly increases the conductivity of the TiO2 films; however, filament formation is not observed after IL gating alone. Replacing the IL with a more conductive aqueous electrolyte contact and biasing does produce electroformed conductive filaments, consistent with a requirement for Joule heating to enhance the vacancy concentration and mobility at specific locations in the film.

  View details for DOI 10.1021/acs.nanolett.7b01460

  View details for PubMedID 28604007

• Absorptive pinhole collimators for ballistic Dirac fermions in graphene NATURE COMMUNICATIONS Barnard, A. W., Hughes, A., Sharpe, A. L., Watanabe, K., Taniguchi, T., Goldhaber-Gordon, D. 2017; 8

  Abstract

  Ballistic electrons in solids can have mean free paths far larger than the smallest features patterned by lithography. This has allowed development and study of solid-state electron-optical devices such as beam splitters and quantum point contacts, which have informed our understanding of electron flow and interactions. Recently, high-mobility graphene has emerged as an ideal two-dimensional semimetal that hosts unique chiral electron-optical effects due to its honeycomb crystalline lattice. However, this chiral transport prevents the simple use of electrostatic gates to define electron-optical devices in graphene. Here we present a method of creating highly collimated electron beams in graphene based on collinear pairs of slits, with absorptive sidewalls between the slits. By this method, we achieve beams with angular width 18° or narrower, and transmission matching classical ballistic predictions.

  View details for DOI 10.1038/ncomms15418

  View details for Web of Science ID 000401279800001

  View details for PubMedID 28504264

• Crystal truncation rods from miscut surfaces PHYSICAL REVIEW B Petach, T. A., Mehta, A., Toney, M. F., Goldhaber-Gordon, D. 2017; 95 (18)

  View details for DOI 10.1103/PhysRevB.95.184104

  View details for Web of Science ID 000401227800003

• Temperature-dependent optical properties of titanium nitride APPLIED PHYSICS LETTERS Briggs, J. A., Naik, G. V., Zhao, Y., Petach, T. A., Sahasrabuddhe, K., Goldhaber-Gordon, D., Melosh, N. A., Dionne, J. A. 2017; 110 (10)

  View details for DOI 10.1063/1.4977840

  View details for Web of Science ID 000397871800011

• Robust fractional quantum Hall effect in the N=2 Landau level in bilayer graphene NATURE COMMUNICATIONS Diankov, G., Liang, C., Amet, F., Gallagher, P., Lee, M., Bestwick, A. J., Tharratt, K., Coniglio, W., Jaroszynski, J., Watanabe, K., Taniguchi, T., Goldhaber-Gordon, D. 2016; 7

  Abstract

  The fractional quantum Hall effect is a canonical example of electron-electron interactions producing new ground states in many-body systems. Most fractional quantum Hall studies have focussed on the lowest Landau level, whose fractional states are successfully explained by the composite fermion model. In the widely studied GaAs-based system, the composite fermion picture is thought to become unstable for the N≥2 Landau level, where competing many-body phases have been observed. Here we report magneto-resistance measurements of fractional quantum Hall states in the N=2 Landau level (filling factors 4<|ν|<8) in bilayer graphene. In contrast with recent observations of particle-hole asymmetry in the N=0/N=1 Landau levels of bilayer graphene, the fractional quantum Hall states we observe in the N=2 Landau level obey particle-hole symmetry within the fully symmetry-broken Landau level. Possible alternative ground states other than the composite fermions are discussed.

  View details for DOI 10.1038/ncomms13908

  View details for Web of Science ID 000390220800001

  View details for PubMedID 28000663

  View details for PubMedCentralID PMC5187585

• 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

• Ballistic miniband conduction in a graphene superlattice. Science Lee, M., Wallbank, J. R., Gallagher, P., Watanabe, K., Taniguchi, T., Fal'ko, V. I., Goldhaber-Gordon, D. 2016; 353 (6307): 1526-1529

  Abstract

  Rational design of long-period artificial lattices yields effects unavailable in simple solids. The moiré pattern in highly aligned graphene/hexagonal boron nitride (h-BN) heterostructures is a lateral superlattice with high electron mobility and an unusual electronic dispersion whose miniband edges and saddle points can be reached by electrostatic gating. We investigated the dynamics of electrons in moiré minibands by measuring ballistic transport between adjacent local contacts in a magnetic field, known as the transverse electron focusing effect. At low temperatures, we observed caustics of skipping orbits extending over hundreds of superlattice periods, reversals of the cyclotron revolution for successive minibands, and breakdown of cyclotron motion near van Hove singularities. At high temperatures, electron-electron collisions suppress focusing. Probing such miniband conduction properties is a necessity for engineering novel transport behaviors in superlattice devices.

  View details for PubMedID 27708100

• Cotunneling Drag Effect in Coulomb-Coupled Quantum Dots. Physical review letters Keller, A. J., Lim, J. S., Sánchez, D., López, R., Amasha, S., Katine, J. A., Shtrikman, H., Goldhaber-Gordon, D. 2016; 117 (6): 066602-?

  Abstract

  In Coulomb drag, a current flowing in one conductor can induce a voltage across an adjacent conductor via the Coulomb interaction. The mechanisms yielding drag effects are not always understood, even though drag effects are sufficiently general to be seen in many low-dimensional systems. In this Letter, we observe Coulomb drag in a Coulomb-coupled double quantum dot and, through both experimental and theoretical arguments, identify cotunneling as essential to obtaining a correct qualitative understanding of the drag behavior.

  View details for DOI 10.1103/PhysRevLett.117.066602

  View details for PubMedID 27541473

• Voltage-Controlled Interfacial Layering in an Ionic Liquid on SrTiO3 ACS NANO Petach, T. A., Mehta, A., Marks, R., Johnson, B., Toney, M. F., Goldhaber-Gordon, D. 2016; 10 (4): 4565-4569

  Abstract

  One prominent structural feature of ionic liquids near surfaces is formation of alternating layers of anions and cations. However, how this layering responds to an applied potential is poorly understood. We focus on the structure of 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl) trifluorophosphate (BMPY-FAP) near the surface of a strontium titanate (SrTiO3) electric double-layer transistor. Using X-ray reflectivity, we show that at positive bias the individual layers in the ionic liquid double layer thicken and the layering persists further away from the interface. We model the reflectivity using a modified distorted crystal model with alternating cation and anion layers, which allows us to extract the charge density and the potential near the surface. We find that the charge density is strongly oscillatory with and without applied potential and that with an applied gate bias of 4.5 V the first two layers become significantly more cation rich than at zero bias, accumulating about 2.5 × 10(13) cm(-2) excess charge density.

  View details for DOI 10.1021/acsnano.6b00645

  View details for Web of Science ID 000375245000078

  View details for PubMedID 26959226

• Switchable friction enabled by nanoscale self-assembly on graphene NATURE COMMUNICATIONS Gallagher, P., Lee, M., Amet, F., Maksymovych, P., Wang, J., Wang, S., Lu, X., Zhang, G., Watanabe, K., Taniguchi, T., Goldhaber-Gordon, D. 2016; 7

  Abstract

  Graphene monolayers are known to display domains of anisotropic friction with twofold symmetry and anisotropy exceeding 200%. This anisotropy has been thought to originate from periodic nanoscale ripples in the graphene sheet, which enhance puckering around a sliding asperity to a degree determined by the sliding direction. Here we demonstrate that these frictional domains derive not from structural features in the graphene but from self-assembly of environmental adsorbates into a highly regular superlattice of stripes with period 4-6 nm. The stripes and resulting frictional domains appear on monolayer and multilayer graphene on a variety of substrates, as well as on exfoliated flakes of hexagonal boron nitride. We show that the stripe-superlattices can be reproducibly and reversibly manipulated with submicrometre precision using a scanning probe microscope, allowing us to create arbitrary arrangements of frictional domains within a single flake. Our results suggest a revised understanding of the anisotropic friction observed on graphene and bulk graphite in terms of adsorbates.

  View details for DOI 10.1038/ncomms10745

  View details for Web of Science ID 000371037200007

  View details for PubMedID 26902595

  View details for PubMedCentralID PMC4766409

• Fully CMOS-compatible titanium nitride nanoantennas APPLIED PHYSICS LETTERS Briggs, J. A., Naik, G. V., Petach, T. A., Baum, B. K., Goldhaber-Gordon, D., Dionne, J. A. 2016; 108 (5)

  View details for DOI 10.1063/1.4941413

  View details for Web of Science ID 000373055700010

• Resonant magneto-optic Kerr effect in the magnetic topological insulator Cr:(Sb-x,Bi1-x)(2)Te-3 PHYSICAL REVIEW B Patankar, S., Hinton, J. P., Griesmar, J., Orenstein, J., Dodge, J. S., Kou, X., Pan, L., Wang, K. L., Bestwick, A. J., Fox, E. J., Goldhaber-Gordon, D., Wang, J., Zhang, S. 2015; 92 (21)

  View details for DOI 10.1103/PhysRevB.92.214440

  View details for Web of Science ID 000367375200005

• Universal Fermi liquid crossover and quantum criticality in a mesoscopic system. Nature Keller, A. J., Peeters, L., Moca, C. P., Weymann, I., Mahalu, D., Umansky, V., Zaránd, G., Goldhaber-Gordon, D. 2015; 526 (7572): 237-240

  View details for DOI 10.1038/nature15261

  View details for PubMedID 26450057

• Repairing nanoscale devices using electron-beam-induced deposition of platinum JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B Peeters, L., Keller, A. J., Umansky, V., Mahalu, D., Goldhaber-Gordon, D. 2015; 33 (5)

  View details for DOI 10.1116/1.4928718

  View details for Web of Science ID 000361833200029

• Self-sensing cantilevers with integrated conductive coaxial tips for high-resolution electrical scanning probe metrology JOURNAL OF APPLIED PHYSICS Haemmerli, A. J., Harjee, N., Koenig, M., Garcia, A. G., Goldhaber-Gordon, D., Pruitt, B. L. 2015; 118 (3)

  View details for DOI 10.1063/1.4923231

  View details for Web of Science ID 000358429200024

• Precise Quantization of the Anomalous Hall Effect near Zero Magnetic Field PHYSICAL REVIEW LETTERS Bestwick, A. J., Fox, E. J., Kou, X., Pan, L., Wang, K. L., Goldhaber-Gordon, D. 2015; 114 (18)

  Abstract

  We report a nearly ideal quantum anomalous Hall effect in a three-dimensional topological insulator thin film with ferromagnetic doping. Near zero applied magnetic field we measure exact quantization in the Hall resistance to within a part per 10 000 and a longitudinal resistivity under 1  Ω per square, with chiral edge transport explicitly confirmed by nonlocal measurements. Deviations from this behavior are found to be caused by thermally activated carriers, as indicated by an Arrhenius law temperature dependence. Using the deviations as a thermometer, we demonstrate an unexpected magnetocaloric effect and use it to reach near-perfect quantization by cooling the sample below the dilution refrigerator base temperature in a process approximating adiabatic demagnetization refrigeration.

  View details for DOI 10.1103/PhysRevLett.114.187201

  View details for Web of Science ID 000353787800006

  View details for PubMedID 26001016

• 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

• A high-mobility electronic system at an electrolyte-gated oxide surface NATURE COMMUNICATIONS Gallagher, P., Lee, M., Petach, T. A., Stanwyck, S. W., Williams, J. R., Watanabe, K., Taniguchi, T., Goldhaber-Gordon, D. 2015; 6

  Abstract

  Electrolyte gating is a powerful technique for accumulating large carrier densities at a surface. Yet this approach suffers from significant sources of disorder: electrochemical reactions can damage or alter the sample, and the ions of the electrolyte and various dissolved contaminants sit Angstroms from the electron system. Accordingly, electrolyte gating is well suited to studies of superconductivity and other phenomena robust to disorder, but of limited use when reactions or disorder must be avoided. Here we demonstrate that these limitations can be overcome by protecting the sample with a chemically inert, atomically smooth sheet of hexagonal boron nitride. We illustrate our technique with electrolyte-gated strontium titanate, whose mobility when protected with boron nitride improves more than 10-fold while achieving carrier densities nearing 10(14) cm(-2). Our technique is portable to other materials, and should enable future studies where high carrier density modulation is required but electrochemical reactions and surface disorder must be minimized.

  View details for DOI 10.1038/ncomms7437

  View details for Web of Science ID 000352633900021

  View details for PubMedID 25762485

• 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., Mühlbauer, M., Brüne, C., Cui, Y., Lai, K., Kundhikanjana, W., Yang, Y., Baenninger, M., König, M., Ames, C., Buhmann, H., Leubner, P., Molenkamp, L. W., Zhang, S., Goldhaber-Gordon, D., Kelly, M. A., Shen, Z. 2015; 6: 7252-?

  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 PubMedID 26006728

• A high-mobility electronic system at an electrolyte-gated oxide surface. Nature communications Gallagher, P., Lee, M., Petach, T. A., Stanwyck, S. W., Williams, J. R., Watanabe, K., Taniguchi, T., Goldhaber-Gordon, D. 2015; 6: 6437-?

  Abstract

  Electrolyte gating is a powerful technique for accumulating large carrier densities at a surface. Yet this approach suffers from significant sources of disorder: electrochemical reactions can damage or alter the sample, and the ions of the electrolyte and various dissolved contaminants sit Angstroms from the electron system. Accordingly, electrolyte gating is well suited to studies of superconductivity and other phenomena robust to disorder, but of limited use when reactions or disorder must be avoided. Here we demonstrate that these limitations can be overcome by protecting the sample with a chemically inert, atomically smooth sheet of hexagonal boron nitride. We illustrate our technique with electrolyte-gated strontium titanate, whose mobility when protected with boron nitride improves more than 10-fold while achieving carrier densities nearing 10(14) cm(-2). Our technique is portable to other materials, and should enable future studies where high carrier density modulation is required but electrochemical reactions and surface disorder must be minimized.

  View details for DOI 10.1038/ncomms7437

  View details for PubMedID 25762485

• Composite fermions and broken symmetries in graphene. Nature communications Amet, F., Bestwick, A. J., Williams, J. R., Balicas, L., Watanabe, K., Taniguchi, T., Goldhaber-Gordon, D. 2015; 6: 5838-?

  Abstract

  The electronic properties of graphene are described by a Dirac Hamiltonian with a four-fold symmetry of spin and valley. This symmetry may yield novel fractional quantum Hall (FQH) states at high magnetic field depending on the relative strength of symmetry-breaking interactions. However, observing such states in transport remains challenging in graphene, as they are easily destroyed by disorder. In this work, we observe in the first two Landau levels the two-flux composite-fermion sequences of FQH states between each integer filling factor. In particular, the odd-numerator fractions appear between filling factors 1 and 2, suggesting a broken-valley symmetry, consistent with our observation of a gap at charge neutrality and zero field. Contrary to our expectations, the evolution of gaps in a parallel magnetic field suggests that states in the first Landau level are not spin-polarized even up to very large out-of-plane fields.

  View details for DOI 10.1038/ncomms6838

  View details for PubMedID 25562690

• Local imaging of high mobility two-dimensional electron systems with virtual scanning tunneling microscopy APPLIED PHYSICS LETTERS Pelliccione, M., BARTEL, J., Sciambi, A., Pfeiffer, L. N., West, K. W., Goldhaber-Gordon, D. 2014; 105 (18)

  View details for DOI 10.1063/1.4901174

  View details for Web of Science ID 000345000000024

• Gate-tunable superconducting weak link and quantum point contact spectroscopy on a strontium titanate surface NATURE PHYSICS Gallagher, P., Lee, M., Williams, J. R., Goldhaber-Gordon, D. 2014; 10 (10): 748-752

  View details for DOI 10.1038/NPHYS3049

  View details for Web of Science ID 000343225200018

• Mechanism for the large conductance modulation in electrolyte-gated thin gold films PHYSICAL REVIEW B Petach, T. A., Lee, M., Davis, R. C., Mehta, A., Goldhaber-Gordon, D. 2014; 90 (8)

  View details for DOI 10.1103/PhysRevB.90.081108

  View details for Web of Science ID 000341256800001

• Selective Equilibration of Spin-Polarized Quantum Hall Edge States in Graphene PHYSICAL REVIEW LETTERS Amet, F., Williams, J. R., Watanabe, K., Taniguchi, T., Goldhaber-Gordon, D. 2014; 112 (19)

  Abstract

  We report on transport measurements of dual-gated, single-layer graphene devices in the quantum Hall regime, allowing for independent control of the filling factors in adjoining regions. Progress in device quality allows us to study scattering between edge states when the fourfold degeneracy of the Landau level is lifted by electron correlations, causing edge states to be spin and/or valley polarized. In this new regime, we observe a dramatic departure from the equilibration seen in more disordered devices: edge states with opposite spins propagate without mixing. As a result, the degree of equilibration inferred from transport can reveal the spin polarization of the ground state at each filling factor. In particular, the first Landau level is shown to be spin polarized at half filling, providing an independent confirmation of a conclusion of Young et al. [Nat. Phys. 8, 550 (2012). The conductance in the bipolar regime is strongly suppressed, indicating that copropagating edge states, even with the same spin, do not equilibrate along PN interfaces. We attribute this behavior to the formation of an insulating ν = 0 stripe at the PN interface.

  View details for DOI 10.1103/PhysRevLett.112.196601

  View details for Web of Science ID 000335918900010

  View details for PubMedID 24877955

• Emergent SU(4) Kondo physics in a spin-charge-entangled double quantum dot NATURE PHYSICS Keller, A. J., Amasha, S., Weymann, I., Moca, C. P., Rau, I. G., Katine, J. A., Shtrikman, H., Zarand, G., Goldhaber-Gordon, D. 2014; 10 (2): 145-150

  View details for DOI 10.1038/NPHYS2844

  View details for Web of Science ID 000332141800021

• Universal conductance fluctuations in electrolyte-gated SrTiO3 nanostructures APPLIED PHYSICS LETTERS Stanwyck, S. W., Gallagher, P., Williams, J. R., Goldhaber-Gordon, D. 2013; 103 (21)

  View details for DOI 10.1063/1.4832555

  View details for Web of Science ID 000327590400084

• Imaging currents in HgTe quantum wells in the quantum spin Hall regime. Nature materials Nowack, K. C., Spanton, E. M., Baenninger, M., König, M., Kirtley, J. R., Kalisky, B., Ames, C., Leubner, P., Brüne, C., Buhmann, H., Molenkamp, L. W., Goldhaber-Gordon, D., Moler, K. A. 2013; 12 (9): 787-791

  Abstract

  The quantum spin Hall (QSH) state is a state of matter characterized by a non-trivial topology of its band structure, and associated conducting edge channels. The QSH state was predicted and experimentally demonstrated to be realized in HgTe quantum wells. The existence of the edge channels has been inferred from local and non-local transport measurements in sufficiently small devices. Here we directly confirm the existence of the edge channels by imaging the magnetic fields produced by current flowing in large Hall bars made from HgTe quantum wells. These images distinguish between current that passes through each edge and the bulk. On tuning the bulk conductivity by gating or raising the temperature, we observe a regime in which the edge channels clearly coexist with the conducting bulk, providing input to the question of how ballistic transport may be limited in the edge channels. Our results represent a versatile method for characterization of new QSH materials systems.

  View details for DOI 10.1038/nmat3682

  View details for PubMedID 23770727

• Imaging currents in HgTe quantum wells in the quantum spin Hall regime. Nature materials Nowack, K. C., Spanton, E. M., Baenninger, M., König, M., Kirtley, J. R., Kalisky, B., Ames, C., Leubner, P., Brüne, C., Buhmann, H., Molenkamp, L. W., Goldhaber-Gordon, D., Moler, K. A. 2013; 12 (9): 787-791

  Abstract

  The quantum spin Hall (QSH) state is a state of matter characterized by a non-trivial topology of its band structure, and associated conducting edge channels. The QSH state was predicted and experimentally demonstrated to be realized in HgTe quantum wells. The existence of the edge channels has been inferred from local and non-local transport measurements in sufficiently small devices. Here we directly confirm the existence of the edge channels by imaging the magnetic fields produced by current flowing in large Hall bars made from HgTe quantum wells. These images distinguish between current that passes through each edge and the bulk. On tuning the bulk conductivity by gating or raising the temperature, we observe a regime in which the edge channels clearly coexist with the conducting bulk, providing input to the question of how ballistic transport may be limited in the edge channels. Our results represent a versatile method for characterization of new QSH materials systems.

  View details for DOI 10.1038/nmat3682

  View details for PubMedID 23770727

• Direct measurement of current-phase relations in superconductor/topological insulator/superconductor junctions. Nano letters Sochnikov, I., Bestwick, A. J., Williams, J. R., Lippman, T. M., Fisher, I. R., Goldhaber-Gordon, D., Kirtley, J. R., Moler, K. A. 2013; 13 (7): 3086-3092

  Abstract

  Proximity to a superconductor is predicted to induce exotic quantum phases in topological insulators. Here, scanning superconducting quantum interference device (SQUID) microscopy reveals that aluminum superconducting rings with topologically insulating Bi2Se3 junctions exhibit a conventional, nearly sinusoidal 2π-periodic current-phase relations. Pearl vortices occur in longer junctions, indicating suppressed superconductivity in aluminum, probably due to a proximity effect. Our observations establish scanning SQUID as a general tool for characterizing proximity effects and for measuring current-phase relations in new materials systems.

  View details for DOI 10.1021/nl400997k

  View details for PubMedID 23795666

• Direct Measurement of Current-Phase Relations in Superconductor/Topological Insulator/Superconductor Junctions NANO LETTERS Sochnikov, I., Bestwick, A. J., Williams, J. R., Lippman, T. M., Fisher, I. R., Godhaber-Gordon, D., Kirtley, J. R., Moler, K. A. 2013; 13 (7): 3086-3092

  Abstract

  Proximity to a superconductor is predicted to induce exotic quantum phases in topological insulators. Here, scanning superconducting quantum interference device (SQUID) microscopy reveals that aluminum superconducting rings with topologically insulating Bi2Se3 junctions exhibit a conventional, nearly sinusoidal 2π-periodic current-phase relations. Pearl vortices occur in longer junctions, indicating suppressed superconductivity in aluminum, probably due to a proximity effect. Our observations establish scanning SQUID as a general tool for characterizing proximity effects and for measuring current-phase relations in new materials systems.

  View details for DOI 10.1021/nl400997k

  View details for Web of Science ID 000321884300014

• Insulating behavior at the neutrality point in single-layer graphene. Physical review letters Amet, F., Williams, J. R., Watanabe, K., Taniguchi, T., Goldhaber-Gordon, D. 2013; 110 (21): 216601-?

  Abstract

  The fate of the low-temperature conductance at the charge-neutrality (Dirac) point in a single sheet of graphene on boron nitride is investigated down to 20 mK. As the temperature is lowered, the peak resistivity diverges with a power-law behavior and becomes as high as several megohms per square at the lowest temperature, in contrast with the commonly observed saturation of the conductivity. As a perpendicular magnetic field is applied, our device remains insulating and directly transitions to the broken-valley-symmetry, ν=0 quantum Hall state, indicating that the insulating behavior we observe at zero magnetic field is a result of broken valley symmetry. Finally we discuss the possible origins of this effect.

  View details for PubMedID 23745906

• Insulating Behavior at the Neutrality Point in Single-Layer Graphene PHYSICAL REVIEW LETTERS Amet, F., Williams, J. R., Watanabe, K., Taniguchi, T., Goldhaber-Gordon, D. 2013; 110 (21)

  Abstract

  The fate of the low-temperature conductance at the charge-neutrality (Dirac) point in a single sheet of graphene on boron nitride is investigated down to 20 mK. As the temperature is lowered, the peak resistivity diverges with a power-law behavior and becomes as high as several megohms per square at the lowest temperature, in contrast with the commonly observed saturation of the conductivity. As a perpendicular magnetic field is applied, our device remains insulating and directly transitions to the broken-valley-symmetry, ν=0 quantum Hall state, indicating that the insulating behavior we observe at zero magnetic field is a result of broken valley symmetry. Finally we discuss the possible origins of this effect.

  View details for DOI 10.1103/PhysRevLett.110.216601

  View details for Web of Science ID 000319278400015

  View details for PubMedID 23745906

• Spatially Resolved Study of Backscattering in the Quantum Spin Hall State PHYSICAL REVIEW X Koenig, M., Baenninger, M., Garcia, A. G., Harjee, N., Pruitt, B. L., Ames, C., Leubner, P., Bruene, C., Buhmann, H., Molenkamp, L. W., Goldhaber-Gordon, D. 2013; 3 (2)

  View details for DOI 10.1103/PhysRevX.3.021003

  View details for Web of Science ID 000317918200001

• Design of a scanning gate microscope for mesoscopic electron systems in a cryogen-free dilution refrigerator REVIEW OF SCIENTIFIC INSTRUMENTS Pelliccione, M., Sciambi, A., BARTEL, J., Keller, A. J., Goldhaber-Gordon, D. 2013; 84 (3)

  View details for DOI 10.1063/1.4794767

  View details for Web of Science ID 000316966200023

  View details for PubMedID 23556823

• Design of a scanning gate microscope for mesoscopic electron systems in a cryogen-free dilution refrigerator. Review of scientific instruments Pelliccione, M., Sciambi, A., BARTEL, J., Keller, A. J., Goldhaber-Gordon, D. 2013; 84 (3): 033703-?

  Abstract

  We report on our design of a scanning gate microscope housed in a cryogen-free dilution refrigerator with a base temperature of 15 mK. The recent increase in efficiency of pulse tube cryocoolers has made cryogen-free systems popular in recent years. However, this new style of cryostat presents challenges for performing scanning probe measurements, mainly as a result of the vibrations introduced by the cryocooler. We demonstrate scanning with root-mean-square vibrations of 0.8 nm at 3 K and 2.1 nm at 15 mK in a 1 kHz bandwidth with our design. Using Coulomb blockade thermometry on a GaAs/AlGaAs gate-defined quantum dot, we demonstrate an electron temperature of 45 mK.

  View details for DOI 10.1063/1.4794767

  View details for PubMedID 23556823

• Scanning gate microscopy of localized states in wide graphene constrictions PHYSICAL REVIEW B Garcia, A. G., Koenig, M., Goldhaber-Gordon, D., Todd, K. 2013; 87 (8)

  View details for DOI 10.1103/PhysRevB.87.085446

  View details for Web of Science ID 000315483300009

• Extreme Mono layer-Selectivity of Hydrogen-Plasma Reactions with Graphene ACS NANO Diankov, G., Neumann, M., Goldhaber-Gordon, D. 2013; 7 (2): 1324-1332

  Abstract

  We study the effect of remote hydrogen plasma on graphene deposited on SiO₂. We observe strong monolayer selectivity for reactions with plasma species, characterized by isotropic hole formation in the basal plane of monolayers and etching from the sheet edges. The areal density of etch pits on monolayers is 2 orders of magnitude higher than on bilayers or thicker sheets. For bilayer or thicker sheets, the etch pit morphology is also quite different: hexagonal etch pits of uniform size, indicating that etching is highly anisotropic and proceeds from pre-existing defects rather than nucleating continuously as on monolayers. The etch rate displays a pronounced dependence on sample temperature for monolayer and multilayer graphene alike: very slow at room temperature, peaking at 400 °C and suppressed entirely at 700 °C. Applying the same hydrogen plasma treatment to graphene deposited on the much smoother substrate mica leads to very similar phenomenology as on the rougher SiO₂, suggesting that a factor other than substrate roughness controls the reactivity of monolayer graphene with hydrogen plasma species.

  View details for DOI 10.1021/nn304903m

  View details for Web of Science ID 000315618700050

  View details for PubMedID 23327591

• Pseudospin-Resolved Transport Spectroscopy of the Kondo Effect in a Double Quantum Dot PHYSICAL REVIEW LETTERS Amasha, S., Keller, A. J., Rau, I. G., Carmi, A., Katine, J. A., Shtrikman, H., Oreg, Y., Goldhaber-Gordon, D. 2013; 110 (4)

  View details for DOI 10.1103/PhysRevLett.110.046604

  View details for Web of Science ID 000313952500012

• Fabrication of samples for scanning probe experiments on quantum spin Hall effect in HgTe quantum wells JOURNAL OF APPLIED PHYSICS Baenninger, M., Koenig, M., Garcia, A. G., Muehlbauer, M., Ames, C., Leubner, P., Bruene, C., Buhmann, H., Molenkamp, L. W., Goldhaber-Gordon, D. 2012; 112 (10)

  View details for DOI 10.1063/1.4767362

  View details for Web of Science ID 000311969800069

• MAJORANA FERMIONS Doubling down on Majorana NATURE PHYSICS Williams, J. R., Goldhaber-Gordon, D. 2012; 8 (11): 778-779

  View details for DOI 10.1038/nphys2459

  View details for Web of Science ID 000310836700006

• Molecular Junctions of Self-Assembled Monolayers with Conducting Polymer Contacts ACS NANO Neuhausen, A. B., Hosseini, A., Sulpizio, J. A., Chidsey, C. E., Goldhaber-Gordon, D. 2012; 6 (11): 9920-9931

  Abstract

  We present a method to fabricate individually addressable junctions of self-assembled monolayers (SAMs) that builds on previous studies which have shown that soft conductive polymer top contacts virtually eliminate shorts through the SAMs. We demonstrate devices with nanoscale lateral dimensions, representing an order of magnitude reduction in device area, with high yield and relatively low device-to-device variation, improving several features of previous soft contact devices. The devices are formed in pores in an inorganic dielectric layer with features defined by e-beam lithography and dry etching. We replace the aqueous PEDOT:PSS conductive polymer used in prior devices with Aedotron P, a low-viscosity, amphiphilic polymer, allowing incorporation of self-assembled monolayers with either hydrophobic or hydrophilic termination with the same junction geometry and materials. We demonstrate the adaptability of this new design by presenting transport measurements on SAMs composed of alkanethiols with methyl, thiol, carboxyl, and azide terminations. We establish that the observed room-temperature tunnel barrier is primarily a function of monolayer thickness, independent of the terminal group's hydrophilicity. Finally, we investigate the temperature dependence of transport and show that the low-temperature behavior is based on the energy distribution of sites from which carriers can tunnel between the polymer and gold contacts, as described by a model of variable-range hopping transport in a disordered conductor.

  View details for DOI 10.1021/nn3035183

  View details for Web of Science ID 000311521700061

  View details for PubMedID 23035989

• Quantum oscillations from a two-dimensional electron gas at a Mott/band insulator interface APPLIED PHYSICS LETTERS Moetakef, P., Ouellette, D. G., Williams, J. R., Allen, S. J., Balents, L., Goldhaber-Gordon, D., Stemmer, S. 2012; 101 (15)

  View details for DOI 10.1063/1.4758989

  View details for Web of Science ID 000310304900028

• Transmission phase shifts of Kondo impurities PHYSICAL REVIEW B Carmi, A., Oreg, Y., Berkooz, M., Goldhaber-Gordon, D. 2012; 86 (11)

  View details for DOI 10.1103/PhysRevB.86.115129

  View details for Web of Science ID 000309173300003

• Effective Cleaning of Hexagonal Boron Nitride for Graphene Devices NANO LETTERS Garcia, A. G., Neumann, M., Amet, F., Williams, J. R., Watanabe, K., Taniguchi, T., Goldhaber-Gordon, D. 2012; 12 (9): 4449-4454

  Abstract

  Hexagonal boron nitride (h-BN) films have attracted considerable interest as substrates for graphene. ( Dean, C. R. et al. Nat. Nanotechnol. 2010 , 5 , 722 - 6 ; Wang, H. et al. Electron Device Lett. 2011 , 32 , 1209 - 1211 ; Sanchez-Yamagishi, J. et al. Phys. Rev. Lett. 2012 , 108 , 1 - 5 .) We study the presence of organic contaminants introduced by standard lithography and substrate transfer processing on h-BN films exfoliated on silicon oxide substrates. Exposure to photoresist processing adds a large broad luminescence peak to the Raman spectrum of the h-BN flake. This signal persists through typical furnace annealing recipes (Ar/H(2)). A recipe that successfully removes organic contaminants and results in clean h-BN flakes involves treatment in Ar/O(2) at 500 °C.

  View details for DOI 10.1021/nl3011726

  View details for Web of Science ID 000308576000006

  View details for PubMedID 22866696

• Unconventional Josephson Effect in Hybrid Superconductor-Topological Insulator Devices PHYSICAL REVIEW LETTERS Williams, J. R., Bestwick, A. J., Gallagher, P., Hong, S. S., Cui, Y., Bleich, A. S., Analytis, J. G., Fisher, I. R., Goldhaber-Gordon, D. 2012; 109 (5)

  Abstract

  We report on transport properties of Josephson junctions in hybrid superconducting-topological insulator devices, which show two striking departures from the common Josephson junction behavior: a characteristic energy that scales inversely with the width of the junction, and a low characteristic magnetic field for suppressing supercurrent. To explain these effects, we propose a phenomenological model which expands on the existing theory for topological insulator Josephson junctions.

  View details for DOI 10.1103/PhysRevLett.109.056803

  View details for Web of Science ID 000306944200002

  View details for PubMedID 23006196

• Carrier-Controlled Ferromagnetism in SrTiO3 PHYSICAL REVIEW X Moetakef, P., Williams, J. R., Ouellette, D. G., Kajdos, A. P., Goldhaber-Gordon, D., Allen, S. J., Stemmer, S. 2012; 2 (2)

  View details for DOI 10.1103/PhysRevX.2.021014

  View details for Web of Science ID 000310513500002

• 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

• Tunneling spectroscopy of graphene-boron-nitride heterostructures PHYSICAL REVIEW B Amet, F., Williams, J. R., Garcia, A. G., Yankowitz, M., Watanabe, K., Taniguchi, T., Goldhaber-Gordon, D. 2012; 85 (7)

  View details for DOI 10.1103/PhysRevB.85.073405

  View details for Web of Science ID 000300238900001

• 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

• Spin-1/2 Kondo effect in an InAs nanowire quantum dot: Unitary limit, conductance scaling, and Zeeman splitting PHYSICAL REVIEW B Kretinin, A. V., Shtrikman, H., Goldhaber-Gordon, D., Hanl, M., Weichselbaum, A., von Delft, J., Costi, T., Mahalu, D. 2011; 84 (24)

  View details for DOI 10.1103/PhysRevB.84.245316

  View details for Web of Science ID 000298561300010

• Electrolyte Gate-Controlled Kondo Effect in SrTiO3 PHYSICAL REVIEW LETTERS Lee, M., Williams, J. R., Zhang, S., Frisbie, C. D., Goldhaber-Gordon, D. 2011; 107 (25)

  Abstract

  We report low-temperature, high-field magnetotransport measurements of SrTiO(3) gated by an ionic gel electrolyte. A saturating resistance upturn and negative magnetoresistance that signal the emergence of the Kondo effect appear for higher applied gate voltages. This observation, enabled by the wide tunability of the ionic gel-applied electric field, promotes the interpretation of the electric field-effect-induced 2D electron system in SrTiO(3) as an admixture of magnetic Ti(3+) ions, i.e., localized and unpaired electrons, and delocalized electrons that partially fill the Ti 3d conduction band.

  View details for DOI 10.1103/PhysRevLett.107.256601

  View details for PubMedID 22243097

• An integrated capacitance bridge for high-resolution, wide temperature range quantum capacitance measurements (vol 82, 053904, 2011) REVIEW OF SCIENTIFIC INSTRUMENTS Hazeghi, A., Sulpizio, J. A., Diankov, G., Goldhaber-Gordon, D., Wong, H. S. 2011; 82 (12)

  View details for DOI 10.1063/1.3665097

  View details for Web of Science ID 000298643100076

• Coulomb Blockade in an Open Quantum Dot PHYSICAL REVIEW LETTERS Amasha, S., Rau, I. G., Grobis, M., Potok, R. M., Shtrikman, H., Goldhaber-Gordon, D. 2011; 107 (21)

  Abstract

  We report the observation of Coulomb blockade in a quantum dot contacted by two quantum point contacts each with a single fully transmitting mode, a system thought to be well described without invoking Coulomb interactions. Below 50 mK we observe a periodic oscillation in the conductance of the dot with gate voltage, corresponding to a residual quantization of charge. From the temperature and magnetic field dependence, we infer the oscillations are mesoscopic Coulomb blockade, a type of Coulomb blockade caused by electron interference in an otherwise open system.

  View details for DOI 10.1103/PhysRevLett.107.216804

  View details for Web of Science ID 000297136400007

  View details for PubMedID 22181909

• Vertical field-effect transistor based on wave-function extension PHYSICAL REVIEW B Sciambi, A., Pelliccione, M., Lilly, M. P., Bank, S. R., Gossard, A. C., Pfeiffer, L. N., West, K. W., Goldhaber-Gordon, D. 2011; 84 (8)

  View details for DOI 10.1103/PhysRevB.84.085301

  View details for Web of Science ID 000294026900004

• An integrated capacitance bridge for high-resolution, wide temperature range quantum capacitance measurements REVIEW OF SCIENTIFIC INSTRUMENTS Hazeghi, A., Sulpizio, J. A., Diankov, G., Goldhaber-Gordon, D., Wong, H. S. 2011; 82 (5)

  Abstract

  We have developed a highly sensitive integrated capacitance bridge for quantum capacitance measurements. Our bridge, based on a GaAs HEMT amplifier, delivers attofarad (aF) resolution using a small AC excitation at or below k(B)T over a broad temperature range (4-300 K). We have achieved a resolution at room temperature of 60 aF/√Hz for a 10  mV ac excitation at 17.5 kHz, with an improved resolution at cryogenic temperatures, for the same excitation amplitude. We demonstrate the utility of our bridge for measuring the quantum capacitance of nanostructures by measuring the capacitance of top-gated graphene devices and cleanly resolving the density of states.

  View details for DOI 10.1063/1.3582068

  View details for PubMedID 21639515

• NANOELECTRONICS Making light of electrons NATURE NANOTECHNOLOGY Goldhaber-Gordon, D. 2011; 6 (4): 196-197

  Abstract

  Electrons have been channelled through graphene wires using the principles of optical guiding by fibre optic cables.

  View details for DOI 10.1038/nnano.2011.53

  View details for Web of Science ID 000289199700003

  View details for PubMedID 21468106

• Virtual scanning tunneling microscopy: A local spectroscopic probe of two-dimensional electron systems (vol 97, 132103, 2010) APPLIED PHYSICS LETTERS Sciambi, A., Pelliccione, M., Bank, S. R., Gossard, A. C., Goldhaber-Gordon, D. 2011; 98 (8)

  View details for DOI 10.1063/1.3554334

  View details for Web of Science ID 000287764300099

• Local interlayer tunneling between two-dimensional electron systems in the ballistic regime PHYSICAL REVIEW B Luna, K., Kim, E., Oreto, P., Kivelson, S. A., Goldhaber-Gordon, D. 2010; 82 (23)

  View details for DOI 10.1103/PhysRevB.82.235317

  View details for Web of Science ID 000286769600003

• Dip-Pen Nanolithography of Electrical Contacts to Single Graphene Flakes ACS NANO Wang, W. M., Stander, N., Stoltenberg, R. M., Goldhaber-Gordon, D., Bao, Z. 2010; 4 (11): 6409-6416

  Abstract

  This study evaluates an alternative to electron-beam lithography for fabricating nanoscale graphene devices. Dip-pen nanolithography is used for defining monolayer graphene flakes and for patterning of gold electrodes through writing of an alkylthiol on thin films of gold evaporated onto graphene flakes. A wet gold etching step was used to form the individual devices. The sheet resistances of these monolayer graphene devices are comparable to reported literature values. This alternative technique for making electrical contact to 2D nanostructures provides a platform for fundamental studies of nanomaterial properties. The merits of using dip-pen nanolithography include lack of electron-beam irradiation damage and targeted patterning of individual devices with imaging and writing conducted in the same instrument under ambient conditions.

  View details for DOI 10.1021/nn101324x

  View details for Web of Science ID 000284438000015

  View details for PubMedID 20945878

• Spatially probed electron-electron scattering in a two-dimensional electron gas PHYSICAL REVIEW B Jura, M. P., Grobis, M., Topinka, M. A., Pfeiffer, L. N., West, K. W., Goldhaber-Gordon, D. 2010; 82 (15)

  View details for DOI 10.1103/PhysRevB.82.155328

  View details for Web of Science ID 000286342900005

• Virtual scanning tunneling microscopy: A local spectroscopic probe of two-dimensional electron systems APPLIED PHYSICS LETTERS Sciambi, A., Pelliccione, M., Bank, S. R., Gossard, A. C., Goldhaber-Gordon, D. 2010; 97 (13)

  View details for DOI 10.1063/1.3492440

  View details for Web of Science ID 000282443800035

• Observation of a one-dimensional spin-orbit gap in a quantum wire NATURE PHYSICS Quay, C. H., Hughes, T. L., Sulpizio, J. A., Pfeiffer, L. N., Baldwin, K. W., West, K. W., Goldhaber-Gordon, D., de Picciotto, R. 2010; 6 (5): 336-339

  View details for DOI 10.1038/NPHYS1626

  View details for Web of Science ID 000278335500011

• Magnetic Doping and Kondo Effect in Bi2Se3 Nanoribbons NANO LETTERS Cha, J. J., Williams, J. R., Kong, D., Meister, S., Peng, H., Bestwick, A. J., Gallagher, P., Goldhaber-Gordon, D., Cui, Y. 2010; 10 (3): 1076-1081

  Abstract

  A simple surface band structure and a large bulk band gap have allowed Bi2Se3 to become a reference material for the newly discovered three-dimensional topological insulators, which exhibit topologically protected conducting surface states that reside inside the bulk band gap. Studying topological insulators such as Bi2Se3 in nanostructures is advantageous because of the high surface-to-volume ratio, which enhances effects from the surface states; recently reported Aharonov-Bohm oscillation in topological insulator nanoribbons by some of us is a good example. Theoretically, introducing magnetic impurities in topological insulators is predicted to open a small gap in the surface states by breaking time-reversal symmetry. Here, we present synthesis of magnetically doped Bi2Se3 nanoribbons by vapor-liquid-solid growth using magnetic metal thin films as catalysts. Although the doping concentration is less than approximately 2%, low-temperature transport measurements of the Fe-doped Bi2Se3 nanoribbon devices show a clear Kondo effect at temperatures below 30 K, confirming the presence of magnetic impurities in the Bi2Se3 nanoribbons. The capability to dope topological insulator nanostructures magnetically opens up exciting opportunities for spintronics.

  View details for DOI 10.1021/nl100146n

  View details for Web of Science ID 000275278200057

  View details for PubMedID 20131918

• Disorder-induced gap behavior in graphene nanoribbons PHYSICAL REVIEW B Gallagher, P., Todd, K., Goldhaber-Gordon, D. 2010; 81 (11)

  View details for DOI 10.1103/PhysRevB.81.115409

  View details for Web of Science ID 000276248800122

• COAXIAL TIP PIEZORESISTIVE SCANNING PROBES FOR HIGH-RESOLUTION ELECTRICAL IMAGING 23rd IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2010) HARJEE, N., Garcia, A. G., Koenig, M., Doll, J. C., Goldhaber-Gordon, D., Pruitt, B. L. IEEE. 2010: 344–347

  View details for Web of Science ID 000278416400084

• Coaxial Tip Piezoresistive Scanning Probes with Sub-Nanometer Vertical Displacement Resolution 2010 IEEE Sensors Conference Harjee, N., Haemmerli, A., Goldhaber-Gordon, D., Pruitt, B. L. IEEE. 2010: 1962–1966

  View details for Web of Science ID 000287982100431

• Electron interferometer formed with a scanning probe tip and quantum point contact PHYSICAL REVIEW B Jura, M. P., Topinka, M. A., Grobis, M., Pfeiffer, L. N., West, K. W., Goldhaber-Gordon, D. 2009; 80 (4)

  View details for DOI 10.1103/PhysRevB.80.041303

  View details for Web of Science ID 000268618100009

• Charge Transport in Interpenetrating Networks of Semiconducting and Metallic Carbon Nanotubes NANO LETTERS Topinka, M. A., Rowell, M. W., Goldhaber-Gordon, D., McGehee, M. D., Hecht, D. S., Gruner, G. 2009; 9 (5): 1866-1871

  Abstract

  Carbon nanotube network field effect transistors (CNTN-FETs) are promising candidates for low cost macroelectronics. We investigate the microscopic transport in these devices using electric force microscopy and simulations. We find that in many CNTN-FETs the voltage drops abruptly at a point in the channel where the current is constricted to just one tube. We also model the effect of varying the semiconducting/metallic tube ratio. The effect of Schottky barriers on both conductance within semiconducting tubes and conductance between semiconducting and metallic tubes results in three possible types of CNTN-FETs with fundamentally different gating mechanisms. We describe this with an electronic phase diagram.

  View details for DOI 10.1021/nl803849e

  View details for Web of Science ID 000266157100025

  View details for PubMedID 19331424

• Contact resistance and shot noise in graphene transistors PHYSICAL REVIEW B Cayssol, J., Huard, B., Goldhaber-Gordon, D. 2009; 79 (7)

  View details for DOI 10.1103/PhysRevB.79.075428

  View details for Web of Science ID 000263815800108

• Evidence for Klein Tunneling in Graphene p-n Junctions PHYSICAL REVIEW LETTERS Stander, N., Huard, B., Goldhaber-Gordon, D. 2009; 102 (2)

  Abstract

  Transport through potential barriers in graphene is investigated using a set of metallic gates capacitively coupled to graphene to modulate the potential landscape. When a gate-induced potential step is steep enough, disorder becomes less important and the resistance across the step is in quantitative agreement with predictions of Klein tunneling of Dirac fermions up to a small correction. We also perform magnetoresistance measurements at low magnetic fields and compare them to recent predictions.

  View details for DOI 10.1103/PhysRevLett.102.026807

  View details for Web of Science ID 000262535900059

  View details for PubMedID 19257307

• Quantum Dot Behavior in Graphene Nanoconstrictions NANO LETTERS Todd, K., Chou, H., Amasha, S., Goldhaber-Gordon, D. 2009; 9 (1): 416-421

  Abstract

  Graphene nanoribbons display an imperfectly understood transport gap. We measure transport through nanoribbon devices of several lengths. In long (>/=250 nm) nanoribbons we observe transport through multiple quantum dots in series, while shorter (

  View details for DOI 10.1021/nl803291b

  View details for Web of Science ID 000262519100076

  View details for PubMedID 19099454

• Evidence of the role of contacts on the observed electron-hole asymmetry in graphene PHYSICAL REVIEW B Huard, B., Stander, N., Sulpizio, J. A., Goldhaber-Gordon, D. 2008; 78 (12)

  View details for DOI 10.1103/PhysRevB.78.121402

  View details for Web of Science ID 000259691500011

• An off-board quantum point contact as a sensitive detector of cantilever motion NATURE PHYSICS Poggio, M., Jura, M. P., Degen, C. L., Topinka, M. A., Mamin, H. J., Goldhaber-Gordon, D., Rugar, D. 2008; 4 (8): 635-638

  View details for DOI 10.1038/nphys992

  View details for Web of Science ID 000258326000016

• Universal scaling in nonequilibrium transport through a single channel Kondo dot PHYSICAL REVIEW LETTERS Grobis, M., Rau, I. G., Potok, R. M., Shtrikman, H., Goldhaber-Gordon, D. 2008; 100 (24)

  Abstract

  Scaling laws and universality play an important role in our understanding of critical phenomena and the Kondo effect. We present measurements of nonequilibrium transport through a single-channel Kondo quantum dot at low temperature and bias. We find that the low-energy Kondo conductance is consistent with universality between temperature and bias and is characterized by a quadratic scaling exponent, as expected for the spin-1/2 Kondo effect. We show that the nonequilibrium Kondo transport measurements are well described by a universal scaling function with two scaling parameters.

  View details for DOI 10.1103/PhysRevLett.100.246601

  View details for Web of Science ID 000256942400052

  View details for PubMedID 18643605

• Electron thermal microscopy NANO LETTERS Brintlinger, T., Qi, Y., Baloch, K. H., Goldhaber-Gordon, D., Cumings, J. 2008; 8 (2): 582-585

  Abstract

  We present real-time, nanoscale temperature mapping using a transmission electron microscope and standard phase transitions in metal islands. Islands are deposited on the reverse side of commercially available silicon nitride membranes, while local thermal gradients are produced by Joule heating in a thin wire on the front side of the membrane. Change in contrast due to the liquid-solid transition in the islands allows the mapping of absolute temperature, as above or below the transition temperature, over the entire field-of-view. Experiments demonstrate nanoscale (<100 nm) resolution and video-rate (>30 thermal-images per second) speed, supported by combined electrical and thermal modeling. This provides a generic and adaptable platform for nanoscale thermal characterization independent of strong probe coupling and optical effects.

  View details for DOI 10.1021/nl0729375

  View details for Web of Science ID 000253166200038

  View details for PubMedID 18229968

• Unexpected features of branched flow through high-mobility two-dimensional electron gases NATURE PHYSICS Jura, M. P., Topinka, M. A., Urban, L., Yazdani, A., Shtrikman, H., Pfeiffer, L. N., West, K. W., Goldhaber-Gordon, D. 2007; 3 (12): 841-845

  View details for DOI 10.1038/nphys756

  View details for Web of Science ID 000251456900018

• Magnetic field dependence of the spin-1/2 and spin-1 Kondo effects in a quantum dot PHYSICAL REVIEW B Quay, C. H., Cumings, J., Gamble, S. J., de Picciotto, R., Kataura, H., Goldhaber-Gordon, D. 2007; 76 (24)

  View details for DOI 10.1103/PhysRevB.76.245311

  View details for Web of Science ID 000251986600063

• Transport properties of carbon nanotube C-60 peapods PHYSICAL REVIEW B Quay, C. H., Cumings, J., Gamble, S. J., Yazdani, A., Kataura, H., Goldhaber-Gordon, D. 2007; 76 (7)

  View details for DOI 10.1103/PhysRevB.76.073404

  View details for Web of Science ID 000249155300027

• Transport measurements across a tunable potential barrier in graphene PHYSICAL REVIEW LETTERS Huard, B., Sulpizio, J. A., Stander, N., Todd, K., Yang, B., Goldhaber-Gordon, D. 2007; 98 (23)

  Abstract

  The peculiar nature of electron scattering in graphene is among many exciting theoretical predictions for the physical properties of this material. To investigate electron scattering properties in a graphene plane, we have created a gate-tunable potential barrier within a single-layer graphene sheet. We report measurements of electrical transport across this structure as the tunable barrier potential is swept through a range of heights. When the barrier is sufficiently strong to form a bipolar junction (n-p-n or p-n-p) within the graphene sheet, the resistance across the barrier sharply increases. We compare these results to predictions for both diffusive and ballistic transport, as the barrier rises on a length scale comparable to the mean free path. Finally, we show how a magnetic field modifies transport across the barrier.

  View details for DOI 10.1103/PhysRevLett.98.236803

  View details for Web of Science ID 000247107200041

  View details for PubMedID 17677928

• Charge rearrangement and screening in a quantum point contact PHYSICAL REVIEW LETTERS Luescher, S., Moore, L. S., Rejec, T., Meir, Y., Shtrikman, H., Goldhaber-Gordon, D. 2007; 98 (19)

  Abstract

  Compressibility measurements are performed on a quantum point contact (QPC). Screening due to mobile charges in the QPC is measured quantitatively, using a second point contact. These measurements are performed from pinch-off through the opening of the first few modes in the QPC. While the measured signal closely matches a Thomas-Fermi-Poisson prediction, deviations from the classical behavior are apparent near the openings of the different modes. Density functional calculations attribute the deviations to a combination of a diverging density of states at the opening of each one-dimensional mode and exchange interaction, which is strongest for the first mode.

  View details for DOI 10.1103/PhysRevLett.98.196805

  View details for Web of Science ID 000246413200043

  View details for PubMedID 17677648

• Magnetic lattice surprise NATURE PHYSICS Moore, L. S., Goldhaber-Gordon, D. 2007; 3 (5): 295-296

  View details for DOI 10.1038/nphys610

  View details for Web of Science ID 000246738300006

• Observation of the two-channel Kondo effect NATURE Potok, R. M., Rau, I. G., Shtrikman, H., Oreg, Y., Goldhaber-Gordon, D. 2007; 446 (7132): 167-171

  Abstract

  Some of the most intriguing problems in solid-state physics arise when the motion of one electron dramatically affects the motion of surrounding electrons. Traditionally, such highly correlated electron systems have been studied mainly in materials with complex transition metal chemistry. Over the past decade, researchers have learned to confine one or a few electrons within a nanometre-scale semiconductor 'artificial atom', and to understand and control this simple system in detail(3). Here we combine artificial atoms to create a highly correlated electron system within a nano-engineered semiconductor structure. We tune the system in situ through a quantum phase transition between two distinct states, each a version of the Kondo state, in which a bound electron interacts with surrounding mobile electrons. The boundary between these competing Kondo states is a quantum critical point-namely, the exotic and previously elusive two-channel Kondo state, in which electrons in two reservoirs are entangled through their interaction with a single localized spin.

  View details for DOI 10.1038/nature05556

  View details for Web of Science ID 000244718100036

  View details for PubMedID 17344849

• Nanofabrication of top-gated carbon nanotube-based transistors: Probing electron-electron interactions in one-dimensional systems JOURNAL OF MATERIALS RESEARCH Sulpizio, J. A., Bandic, Z. Z., Goldhaber-Gordon, D. 2006; 21 (11): 2916-2921

  View details for DOI 10.1557/JMR.2006.0361

  View details for Web of Science ID 000241843300025

• Single-electron transistors in GaN/AlGaN heterostructures APPLIED PHYSICS LETTERS Chou, H. T., Goldhaber-Gordon, D., Schmult, S., Manfra, M. J., Sergent, A. M., Molnar, R. J. 2006; 89 (3)

  View details for DOI 10.1063/1.2226454

  View details for Web of Science ID 000239174100087

• Greetings from three generations of Goldhabers to Academician Ginzburg, on the occasion of your 90th birthday JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM Goldhaber, F., Goldhaber, M., Goldhaber-Gordon, D. 2006; 19 (3-5): 467-467

  View details for DOI 10.1007/s10948-006-0174-7

  View details for Web of Science ID 000244404100035

• Quantum transport in high mobility AlGaN/GaN 2DEGs and nanostructures 6th International Conference on Nitride Semiconductors (ICNS-6) Schmult, S., Manfra, M. J., Sergent, A. M., Punnoose, A., Chou, H. T., Goldhaber-Gordon, D., Molnar, R. J. WILEY-V C H VERLAG GMBH. 2006: 1706–12

  View details for DOI 10.1002/pssb.200565378

  View details for Web of Science ID 000238752200060

• Tunable anomalous Hall effect in a nonferromagnetic system PHYSICAL REVIEW LETTERS Cumings, J., Moore, L. S., Chou, H. T., Ku, K. C., Xiang, G., Crooker, S. A., Samarth, N., Goldhaber-Gordon, D. 2006; 96 (19)

  Abstract

  We measure the low-field Hall resistivity of a magnetically doped two-dimensional electron gas as a function of temperature and electrically gated carrier density. Comparing these results with the carrier density extracted from Shubnikov-de Haas oscillations reveals an excess Hall resistivity that increases with decreasing temperature. This excess Hall resistivity qualitatively tracks the paramagnetic polarization of the sample, in analogy to the ferromagnetic anomalous Hall effect. The data are consistent with skew scattering of carriers by disorder near the crossover to localization.

  View details for DOI 10.1103/PhysRevLett.96.196404

  View details for Web of Science ID 000237683600032

  View details for PubMedID 16803118

• Conductance fluctuations and partially broken spin symmetries in quantum dots PHYSICAL REVIEW B Zumbuhl, D. M., MILLER, J. B., Marcus, C. M., Goldhaber-Gordon, D., Harris, J. S., Campman, K., Gossard, A. C. 2005; 72 (8)

  View details for DOI 10.1103/PhysRevB.72.081305

  View details for Web of Science ID 000231564600008

• Electron microscopy of the operation of nanoscale devices. Microscopy and microanalysis Cummings, J., Goldhaber-Gordon, D., Zettl, A., McCartney, M. R., Spence, J. C. 2005; 11: 1504-1505

  Abstract

  Extended abstract of a paper presented at Microscopy and Microanalysis 2005 in Honolulu, Hawaii, USA, July 31--August 4, 2005.

  View details for DOI 10.1017/S1431927605510444

  View details for PubMedID 24017620

• Nanotechnology - New spin on correlated electrons NATURE Potok, R. M., Goldhaber-Gordon, D. 2005; 434 (7032): 451-452

  View details for DOI 10.1038/434451a

  View details for Web of Science ID 000227836000027

  View details for PubMedID 15791241

• Schrodinger's mousetrap - Part 6: A cryptic response. NATURE Goldhaber-Gordon, I., Goldhaber-Gordon, D. 2005; 433 (7028): 805-805

  View details for DOI 10.1038/433805a

  View details for Web of Science ID 000227174600021

• Schrödinger's mousetrap. Part 6. Nature Goldhaber-Gordon, I., Goldhaber-Gordon, D. 2005; 433 (7028): 805-?

  View details for PubMedID 15729319

• High-quality quantum point contacts in GaN/AlGaN heterostructures APPLIED PHYSICS LETTERS Chou, H. T., Luscher, S., Goldhaber-Gordon, D., Manfra, M. J., Sergent, A. M., West, K. W., Molnar, R. J. 2005; 86 (7)

  View details for DOI 10.1063/1.1862339

  View details for Web of Science ID 000227439400082

• Electron Microscopy of the operation of nanoscale devices Symposium on Electron Microscopy of Molecular and Atom-Scale Mechanical Behavior, Chemistry and Structure held at the 2004 MRS Fall Meeting Cumings, J., Goldhaber-Gordon, D., Zettl, A., McCartney, M. R., Spence, J. C. MATERIALS RESEARCH SOCIETY. 2005: 165–176

  View details for Web of Science ID 000230926900025

• Measurements of Kondo and spin splitting in single-electron transistors PHYSICAL REVIEW LETTERS Kogan, A., Amasha, S., Goldhaber-Gordon, D., Granger, G., Kastner, M. A., Shtrikman, H. 2004; 93 (16)

  Abstract

  We measure the spin splitting in a magnetic field B of localized states in single-electron transistors using a new method, inelastic spin-flip cotunneling. Because it involves only internal excitations, this technique gives the most precise value of the Zeeman energy Delta=/g/mu(B)B. In the same devices we also measure the splitting with B of the Kondo peak in differential conductance. The Kondo splitting appears only above a threshold field as predicted by theory. However, the magnitude of the Kondo splitting at high fields exceeds 2/g/mu(B)B in disagreement with theory.

  View details for DOI 10.1103/PhysRevLett.93.166602

  View details for Web of Science ID 000224533300062

  View details for PubMedID 15525018

• Two-channel Kondo effect in a modified single electron transistor NATO Advanced Research Workshop on Molecular Nanowires and Other Quantum Objects Oreg, Y., Goldhaber-Gordon, D. SPRINGER. 2004: 67–76

  View details for Web of Science ID 000222494700007

• Kondo effect and spin filtering in triangular artificial atoms SOLID STATE COMMUNICATIONS Zarand, G., Brataas, A., Goldhaber-Gordon, D. 2003; 126 (8): 463-466

  View details for DOI 10.1016/S0038-1098(03)00180-7

  View details for Web of Science ID 000182901400008

• Two-channel Kondo effect in a modified single electron transistor PHYSICAL REVIEW LETTERS Oreg, Y., Goldhaber-Gordon, D. 2003; 90 (13)

  Abstract

  We suggest a simple system of two electron droplets which should display two-channel Kondo behavior at experimentally accessible temperatures. Stabilization of the two-channel Kondo fixed point requires fine control of the electrochemical potential in each droplet, which can be achieved by adjusting voltages on nearby gate electrodes. We study the conditions for obtaining this type of two-channel Kondo behavior, discuss the experimentally observable consequences, and explore the generalization to the multichannel Kondo case.

  View details for DOI 10.1103/PhysRevLett.90.136602

  View details for Web of Science ID 000182032600045

  View details for PubMedID 12689314

• Singlet-triplet transition in a single-electron transistor at zero magnetic field PHYSICAL REVIEW B Kogan, A., Granger, G., Kastner, M. A., Goldhaber-Gordon, D., Shtrikman, H. 2003; 67 (11)

  View details for DOI 10.1103/PhysRevB.67.113309

  View details for Web of Science ID 000182035100017

• Gate-controlled spin-orbit quantum interference effects in lateral transport PHYSICAL REVIEW LETTERS MILLER, J. B., Zumbuhl, D. M., Marcus, C. M., Lyanda-Geller, Y. B., Goldhaber-Gordon, D., Campman, K., Gossard, A. C. 2003; 90 (7)

  Abstract

  In situ control of spin-orbit coupling in coherent transport using a clean GaAs/AlGaAs two-dimensional electron gas is realized, leading to a gate-tunable crossover from weak localization to antilocalization. The necessary theory of 2D magnetotransport in the presence of spin-orbit coupling beyond the diffusive approximation is developed and used to analyze experimental data. With this theory the Rashba contribution and linear and cubic Dresselhaus contributions to spin-orbit coupling are separately estimated, allowing the angular dependence of spin-orbit precession to be extracted at various gate voltages.

  View details for DOI 10.1103/PhysRevLett.90.076807

  View details for Web of Science ID 000181090800043

  View details for PubMedID 12633263

• Low-temperature fate of the 0.7 structure in a point contact: A Kondo-like correlated state in an open system PHYSICAL REVIEW LETTERS Cronenwett, S. M., Lynch, H. J., Goldhaber-Gordon, D., Kouwenhoven, L. P., Marcus, C. M., Hirose, K., Wingreen, N. S., Umansky, V. 2002; 88 (22)

  Abstract

  Besides the usual conductance plateaus at multiples of 2e(2)/h, quantum point contacts typically show an extra plateau at approximately 0.7(2e(2)/h), believed to arise from electron-electron interactions that prohibit the two spin channels from being simultaneously occupied. We present evidence that the disappearance of the 0.7 structure at very low temperature signals the formation of a Kondo-like correlated spin state. Evidence includes a zero-bias conductance peak that splits in a parallel field, scaling of conductance to a modified Kondo form, and consistency between peak width and the Kondo temperature.

  View details for DOI 10.1103/PhysRevLett.88.226805

  View details for Web of Science ID 000175709100037

  View details for PubMedID 12059445

• Temperature dependence of Fano line shapes in a weakly coupled single-electron transistor PHYSICAL REVIEW B Zacharia, I. G., Goldhaber-Gordon, D., Granger, G., Kastner, M. A., Khavin, Y. B., Shtrikman, H., Mahalu, D., Meirav, U. 2001; 64 (15)

  View details for Web of Science ID 000171694600055

• Molecular electronics - Momentous period for nanotubes NATURE Goldhaber-Gordon, D., Goldhaber-Gordon, I. 2001; 412 (6847): 594-?

  View details for Web of Science ID 000170318000023

  View details for PubMedID 11493901

• Coulomb-blockade spectroscopy on a small quantum dot in a parallel magnetic field APPLIED PHYSICS LETTERS Duncan, D. S., Goldhaber-Gordon, D., Westervelt, R. M., Maranowski, K. D., Gossard, A. C. 2000; 77 (14): 2183-2185

  View details for Web of Science ID 000089524900035

• Fano resonances in electronic transport through a single-electron transistor PHYSICAL REVIEW B Gores, J., Goldhaber-Gordon, D., Heemeyer, S., Kastner, M. A., Shtrikman, H., Mahalu, D., Meirav, U. 2000; 62 (3): 2188-2194

  View details for Web of Science ID 000088335600117

• Suppression of the Kondo effect in a quantum dot by microwave radiation International Conference on Electron Transport in Mesoscopic Systems (ETMS '99) Elzerman, J. M., De Franceschi, S., Goldhaber-Gordon, D., van der Wiel, W. G., Kouwenhoven, L. P. SPRINGER/PLENUM PUBLISHERS. 2000: 375–89

  View details for Web of Science ID 000085997700013

• From the Kondo regime to the mixed-valence regime in a single-electron transistor PHYSICAL REVIEW LETTERS Goldhaber-Gordon, D., Gores, J., Kastner, M. A., Shtrikman, H., Mahalu, D., Meirav, U. 1998; 81 (23): 5225-5228

  View details for Web of Science ID 000077362300047

• Kondo effect in a single-electron transistor NATURE Goldhaber-Gordon, D., Shtrikman, H., Mahalu, D., Abusch-Magder, D., Meirav, U., Kastner, M. A. 1998; 391 (6663): 156-159

  View details for Web of Science ID 000071380900044

• Magnetic-field dependence of the level spacing of a small electron droplet PHYSICAL REVIEW B Klein, O., Goldhaber-Gordon, D., Chamon, C. D., Kastner, M. A. 1996; 53 (8): R4221-R4224

  View details for Web of Science ID A1996TZ17700008

• Phase transitions in artificial atoms NATO Advanced Study Institute on Quantum Transport in Semiconductor Submicron Structures Klein, O., Chamon, C. D., GoldhaberGordon, D., Kastner, M. A., Wen, X. G. SPRINGER. 1996: 239–249

  View details for Web of Science ID A1996BH46P00011