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Mikheev E, Rosen IT, Goldhaber-Gordon D. Quantized critical supercurrent in SrTiO 3-based quantum point contacts. SCIENCE ADVANCES 2021; 7:eabi6520. [PMID: 34597141 PMCID: PMC10938545 DOI: 10.1126/sciadv.abi6520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 08/11/2021] [Indexed: 06/13/2023]
Abstract
Superconductivity in SrTiO3 occurs at remarkably low carrier densities and therefore, unlike conventional superconductors, can be controlled by electrostatic gates. Here, we demonstrate nanoscale weak links connecting superconducting leads, all within a single material, SrTiO3. Ionic liquid gating accumulates carriers in the leads, and local electrostatic gates are tuned to open the weak link. These devices behave as superconducting quantum point contacts with a quantized critical supercurrent. This is a milestone toward establishing SrTiO3 as a single-material platform for mesoscopic superconducting transport experiments that also intrinsically contains the necessary ingredients to engineer topological superconductivity.
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Affiliation(s)
- Evgeny Mikheev
- Department of Physics, Stanford University, Stanford, CA 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - Ilan T. Rosen
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
- Department of Applied Physics, Stanford University, Stanford, CA 94305, USA
| | - David Goldhaber-Gordon
- Department of Physics, Stanford University, Stanford, CA 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
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2
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Kumar S, Pepper M. Interactions and non-magnetic fractional quantization in one-dimension. APPLIED PHYSICS LETTERS 2021; 119:110502. [PMID: 35382142 PMCID: PMC8970604 DOI: 10.1063/5.0061921] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 08/27/2021] [Indexed: 06/14/2023]
Abstract
In this Perspective article, we present recent developments on interaction effects on the carrier transport properties of one-dimensional (1D) semiconductor quantum wires fabricated using the GaAs/AlGaAs system, particularly the emergence of the long predicted fractional quantization of conductance in the absence of a magnetic field. Over three decades ago, it was shown that transport through a 1D system leads to integer quantized conductance given by N·2e2/h, where N is the number of allowed energy levels (N = 1, 2, 3, …). Recent experiments have shown that a weaker confinement potential and low carrier concentration provide a testbed for electrons strongly interacting. The consequence leads to a reconfiguration of the electron distribution into a zigzag assembly which, unexpectedly, was found to exhibit quantization of conductance predominantly at 1/6, 2/5, 1/4, and 1/2 in units of e2/h. These fractional states may appear similar to the fractional states seen in the Fractional Quantum Hall Effect; however, the system does not possess a filling factor and they differ in the nature of their physical causes. The states may have promise for the emergent topological quantum computing schemes as they are controllable by gate voltages with a distinct identity.
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Affiliation(s)
- S. Kumar
- Author to whom correspondence should be addressed:
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3
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Kraft R, Krainov IV, Gall V, Dmitriev AP, Krupke R, Gornyi IV, Danneau R. Valley Subband Splitting in Bilayer Graphene Quantum Point Contacts. PHYSICAL REVIEW LETTERS 2018; 121:257703. [PMID: 30608811 DOI: 10.1103/physrevlett.121.257703] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Indexed: 06/09/2023]
Abstract
We report a study of one-dimensional subband splitting in a bilayer graphene quantum point contact in which quantized conductance in steps of 4e^{2}/h is clearly defined down to the lowest subband. While our source-drain bias spectroscopy measurements reveal an unconventional confinement, we observe a full lifting of the valley degeneracy at high magnetic fields perpendicular to the bilayer graphene plane for the first two lowest subbands where confinement and Coulomb interactions are the strongest and a peculiar merging or mixing of K and K^{'} valleys from two nonadjacent subbands with indices (N,N+2), which are well described by our semiphenomenological model.
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Affiliation(s)
- R Kraft
- Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
| | - I V Krainov
- A.F. Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia
- Lappeenranta University of Technology, P.O. Box 20, 53851 Lappeenranta, Finland
| | - V Gall
- Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
- Institute for Condensed Matter Theory, Karlsruhe Institute of Technology, D-76128 Karlsruhe, Germany
| | - A P Dmitriev
- A.F. Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia
| | - R Krupke
- Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
- Department of Materials and Earth Sciences, Technical University Darmstadt, 64287 Darmstadt, Germany
| | - I V Gornyi
- Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
- A.F. Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia
- Institute for Condensed Matter Theory, Karlsruhe Institute of Technology, D-76128 Karlsruhe, Germany
| | - R Danneau
- Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
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Ho SC, Chang HJ, Chang CH, Lo ST, Creeth G, Kumar S, Farrer I, Ritchie D, Griffiths J, Jones G, Pepper M, Chen TM. Imaging the Zigzag Wigner Crystal in Confinement-Tunable Quantum Wires. PHYSICAL REVIEW LETTERS 2018; 121:106801. [PMID: 30240231 DOI: 10.1103/physrevlett.121.106801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/03/2018] [Indexed: 06/08/2023]
Abstract
The existence of Wigner crystallization, one of the most significant hallmarks of strong electron correlations, has to date only been definitively observed in two-dimensional systems. In one-dimensional (1D) quantum wires Wigner crystals correspond to regularly spaced electrons; however, weakening the confinement and allowing the electrons to relax in a second dimension is predicted to lead to the formation of a new ground state constituting a zigzag chain with nontrivial spin phases and properties. Here we report the observation of such zigzag Wigner crystals by use of on-chip charge and spin detectors employing electron focusing to image the charge density distribution and probe their spin properties. This experiment demonstrates both the structural and spin phase diagrams of the 1D Wigner crystallization. The existence of zigzag spin chains and phases which can be electrically controlled in semiconductor systems may open avenues for experimental studies of Wigner crystals and their technological applications in spintronics and quantum information.
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Affiliation(s)
- Sheng-Chin Ho
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Heng-Jian Chang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Chia-Hua Chang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Shun-Tsung Lo
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Graham Creeth
- Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom
| | - Sanjeev Kumar
- Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom
| | - Ian Farrer
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
- Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, United Kingdom
| | - David Ritchie
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Jonathan Griffiths
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Geraint Jones
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Michael Pepper
- Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom
| | - Tse-Ming Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
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5
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Gul Y, Holmes SN, Myronov M, Kumar S, Pepper M. Self-organised fractional quantisation in a hole quantum wire. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:09LT01. [PMID: 29381143 DOI: 10.1088/1361-648x/aaabab] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We have investigated hole transport in quantum wires formed by electrostatic confinement in strained germanium two-dimensional layers. The ballistic conductance characteristics show the regular staircase of quantum levels with plateaux at n2e 2/h, where n is an integer, e is the fundamental unit of charge and h is Planck's constant. However as the carrier concentration is reduced, the quantised levels show a behaviour that is indicative of the formation of a zig-zag structure and new quantised plateaux appear at low temperatures. In units of 2e 2/h the new quantised levels correspond to values of n = 1/4 reducing to 1/8 in the presence of a strong parallel magnetic field which lifts the spin degeneracy but does not quantise the wavefunction. A further plateau is observed corresponding to n = 1/32 which does not change in the presence of a parallel magnetic field. These values indicate that the system is behaving as if charge was fractionalised with values e/2 and e/4, possible mechanisms are discussed.
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Affiliation(s)
- Y Gul
- London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London, Torrington Place, London, WC1E 7JE, United Kingdom
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Pepper M, Thornton TJ, Wharam DA. Early work on semiconductor quantum nanoelectronics in the Cavendish Laboratory. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:421003. [PMID: 27557363 DOI: 10.1088/0953-8984/28/42/421003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Affiliation(s)
- M Pepper
- London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK. School of Electrical, Computer, and Energy Engineering, Arizona State University, PO Box 875706, Tempe, AZ 85287-5706, USA. Eberhard-Karls-University Tübingen, Institute of Applied Physics, Auf der Morgenstelle 10, D-72076 Tübingen, Germany
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7
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Wigner and Kondo physics in quantum point contacts revealed by scanning gate microscopy. Nat Commun 2014; 5:4290. [DOI: 10.1038/ncomms5290] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 06/04/2014] [Indexed: 11/09/2022] Open
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8
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Burke AM, Klochan O, Farrer I, Ritchie DA, Hamilton AR, Micolich AP. Extreme sensitivity of the spin-splitting and 0.7 anomaly to confining potential in one-dimensional nanoelectronic devices. NANO LETTERS 2012; 12:4495-4502. [PMID: 22830617 DOI: 10.1021/nl301566d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Quantum point contacts (QPCs) have shown promise as nanoscale spin-selective components for spintronic applications and are of fundamental interest in the study of electron many-body effects such as the 0.7 × 2e(2)/h anomaly. We report on the dependence of the 1D Landé g-factor g and 0.7 anomaly on electron density and confinement in QPCs with two different top-gate architectures. We obtain g values up to 2.8 for the lowest 1D subband, significantly exceeding previous in-plane g-factor values in AlGaAs/GaAs QPCs and approaching that in InGaAs/InP QPCs. We show that g is highly sensitive to confinement potential, particularly for the lowest 1D subband. This suggests careful management of the QPC's confinement potential may enable the high g desirable for spintronic applications without resorting to narrow-gap materials such as InAs or InSb. The 0.7 anomaly and zero-bias peak are also highly sensitive to confining potential, explaining the conflicting density dependencies of the 0.7 anomaly in the literature.
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Affiliation(s)
- A M Burke
- School of Physics, University of New South Wales, Sydney NSW 2052, Australia.
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9
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Das PP, Bhandari NK, Wan J, Charles J, Cahay M, Chetry KB, Newrock RS, Herbert ST. Influence of surface scattering on the anomalous conductance plateaus in an asymmetrically biased InAs/In(0.52)Al(0.48)As quantum point contact. NANOTECHNOLOGY 2012; 23:215201. [PMID: 22551945 DOI: 10.1088/0957-4484/23/21/215201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We study of the appearance and evolution of several anomalous (i.e., G < G(0) D 2e(2)/h) conductance plateaus in an In(0.52)Al(0.48)As/InAs quantum point contact (QPC). This work was performed at T = 4:2 K as a function of the offset bias ΔV(G) between the two in-plane gates of the QPC. The number and location of the anomalous conductance plateaus strongly depend on the polarity of the offset bias. The anomalous plateaus appear only over an intermediate range of offset bias of several volts. They are quite robust, being observed over a maximum range of nearly 1 V for the common sweep voltage applied to the two gates. These results are interpreted as evidence for the sensitivity of the QPC spin polarization to defects (surface roughness and impurity (dangling bond) scattering) generated during the etching process that forms the QPC side walls. This assertion is supported by non-equilibrium Green function simulations of the conductance of a single QPC in the presence of dangling bonds on its walls. Our simulations show that a spin conductance polarization as high as 98% can be achieved despite the presence of dangling bonds. The maximum in is not necessarily reached where the conductance of the channel is equal to 0:5G(0).
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Affiliation(s)
- Partha P Das
- School of Electronics and Computing Systems, University of Cincinnati, Cincinnati, OH 45221, USA
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10
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Micolich AP. What lurks below the last plateau: experimental studies of the 0.7 × 2e(2)/h conductance anomaly in one-dimensional systems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:443201. [PMID: 21997403 DOI: 10.1088/0953-8984/23/44/443201] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The integer quantised conductance of one-dimensional electron systems is a well-understood effect of quantum confinement. A number of fractionally quantised plateaus are also commonly observed. They are attributed to many-body effects, but their precise origin is still a matter of debate, having attracted considerable interest over the past 15 years. This review reports on experimental studies of fractionally quantised plateaus in semiconductor quantum point contacts and quantum wires, focusing on the 0.7 × 2e(2)/h conductance anomaly, its analogues at higher conductances and the zero-bias peak observed in the dc source-drain bias for conductances less than 2e(2)/h.
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Affiliation(s)
- A P Micolich
- School of Physics, University of New South Wales, Sydney, NSW 2052, Australia.
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11
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Feiguin AE, Fiete GA. Spin-incoherent behavior in the ground state of strongly correlated systems. PHYSICAL REVIEW LETTERS 2011; 106:146401. [PMID: 21561205 DOI: 10.1103/physrevlett.106.146401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Indexed: 05/30/2023]
Abstract
It is commonly believed that strongly interacting one-dimensional Fermi systems with gapless excitations are effectively described by Luttinger liquid theory. However, when the temperature of the system is high compared to the spin energy, but small compared to the charge energy, the system becomes "spin incoherent." We present numerical evidence showing that the one-dimensional "t-J-Kondo" lattice, consisting of a t-J chain interacting with localized spins, displays all the characteristic signatures of spin-incoherent physics, but in the ground state. We argue that similar physics may be present in a wide range of strongly interacting systems.
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Affiliation(s)
- Adrian E Feiguin
- Department of Physics and Astronomy, University of Wyoming, Laramie, Wyoming 82071, USA
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12
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Uddin LQ, Supekar K, Amin H, Rykhlevskaia E, Nguyen DA, Greicius MD, Menon V. Dissociable connectivity within human angular gyrus and intraparietal sulcus: evidence from functional and structural connectivity. Cereb Cortex 2010; 20:2636-46. [PMID: 20154013 PMCID: PMC2951845 DOI: 10.1093/cercor/bhq011] [Citation(s) in RCA: 354] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The inferior parietal lobule (IPL) of the human brain is a heterogeneous region involved in visuospatial attention, memory, and mathematical cognition. Detailed description of connectivity profiles of subdivisions within the IPL is critical for accurate interpretation of functional neuroimaging studies involving this region. We separately examined functional and structural connectivity of the angular gyrus (AG) and the intraparietal sulcus (IPS) using probabilistic cytoarchitectonic maps. Regions-of-interest (ROIs) included anterior and posterior AG subregions (PGa, PGp) and 3 IPS subregions (hIP2, hIP1, and hIP3). Resting-state functional connectivity analyses showed that PGa was more strongly linked to basal ganglia, ventral premotor areas, and ventrolateral prefrontal cortex, while PGp was more strongly connected with ventromedial prefrontal cortex, posterior cingulate, and hippocampus-regions comprising the default mode network. The anterior-most IPS ROIs, hIP2 and hIP1, were linked with ventral premotor and middle frontal gyrus, while the posterior-most IPS ROI, hIP3, showed connectivity with extrastriate visual areas. In addition, hIP1 was connected with the insula. Tractography using diffusion tensor imaging revealed structural connectivity between most of these functionally connected regions. Our findings provide evidence for functional heterogeneity of cytoarchitectonically defined subdivisions within IPL and offer a novel framework for synthesis and interpretation of the task-related activations and deactivations involving the IPL during cognition.
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Affiliation(s)
- Lucina Q Uddin
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA 94304, USA.
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13
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Cortes-Huerto R, Ballone P. Spontaneous spin polarization and charge localization in metal nanowires: the role of a geometric constriction. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:295302. [PMID: 21399298 DOI: 10.1088/0953-8984/22/29/295302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
An idealized jellium model of conducting nanowires with a geometric constriction is investigated by density functional theory (DFT) in the local spin density (LSD) approximation. The results reveal a fascinating variety of spin and charge patterns arising in wires of sufficiently low (r(s) ≥ 15) average electron density, pinned at the indentation by an apparent attractive interaction with the constriction. The spin-resolved frequency-dependent conductivity shows a marked asymmetry in the two spin channels, reflecting the spontaneous spin polarization around the wire neck. The relevance of the computational results is discussed in relation to the so-called 0.7 anomaly found by experiments in the low-frequency conductivity of nanowires at near-breaking conditions (see 2008 J. Phys.: Condens Matter 20, special issue on the 0.7 anomaly). Although our mean-field approach cannot account for the intrinsic many-body effects underlying the 0.7 anomaly, it still provides a diagnostic tool to predict impending transitions in the electronic structure.
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Affiliation(s)
- R Cortes-Huerto
- Atomistic Simulation Centre, Queen's University Belfast, Belfast, UK
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14
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Berggren KF, Pepper M. Electrons in one dimension. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2010; 368:1141-62. [PMID: 20123751 PMCID: PMC3263805 DOI: 10.1098/rsta.2009.0226] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
In this article, we present a summary of the current status of the study of the transport of electrons confined to one dimension in very low disorder GaAs-AlGaAs heterostructures. By means of suitably located gates and application of a voltage to 'electrostatically squeeze' the electronic wave functions, it is possible to produce a controllable size quantization and a transition from two-dimensional transport. If the length of the electron channel is sufficiently short, then transport is ballistic and the quantized subbands each have a conductance equal to the fundamental quantum value 2e(2)/h, where the factor of 2 arises from the spin degeneracy. This mode of conduction is discussed, and it is shown that a number of many-body effects can be observed. These effects are discussed as in the spin-incoherent regime, which is entered when the separation of the electrons is increased and the exchange energy is less than kT. Finally, results are presented in the regime where the confinement potential is decreased and the electron configuration relaxes to minimize the electron-electron repulsion to move towards a two-dimensional array. It is shown that the ground state is no longer a line determined by the size quantization alone, but becomes two distinct rows arising from minimization of the electrostatic energy and is the precursor of a two-dimensional Wigner lattice.
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Affiliation(s)
- K.-F. Berggren
- Theory and Modelling, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-58183 Linköping, Sweden
| | - M. Pepper
- London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 6BT, UK
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15
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Debray P, Rahman SMS, Wan J, Newrock RS, Cahay M, Ngo AT, Ulloa SE, Herbert ST, Muhammad M, Johnson M. All-electric quantum point contact spin-polarizer. NATURE NANOTECHNOLOGY 2009; 4:759-764. [PMID: 19893512 DOI: 10.1038/nnano.2009.240] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Accepted: 07/24/2009] [Indexed: 05/28/2023]
Abstract
The controlled creation, manipulation and detection of spin-polarized currents by purely electrical means remains a central challenge of spintronics. Efforts to meet this challenge by exploiting the coupling of the electron orbital motion to its spin, in particular Rashba spin-orbit coupling, have so far been unsuccessful. Recently, it has been shown theoretically that the confining potential of a small current-carrying wire with high intrinsic spin-orbit coupling leads to the accumulation of opposite spins at opposite edges of the wire, though not to a spin-polarized current. Here, we present experimental evidence that a quantum point contact -- a short wire -- made from a semiconductor with high intrinsic spin-orbit coupling can generate a completely spin-polarized current when its lateral confinement is made highly asymmetric. By avoiding the use of ferromagnetic contacts or external magnetic fields, such quantum point contacts may make feasible the development of a variety of semiconductor spintronic devices.
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Affiliation(s)
- P Debray
- Department of Physics, University of Cincinnati, Cincinnati, OH 45221, USA.
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16
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Fiete GA. Singular responses of spin-incoherent Luttinger liquids. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:193201. [PMID: 21825474 DOI: 10.1088/0953-8984/21/19/193201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
When a local potential changes abruptly in time, an electron gas responds by shifting to a new state which at long times is orthogonal to the one in the absence of the local potential. This is known as Anderson's orthogonality catastrophe and it is relevant for the so-called x-ray edge or Fermi-edge singularity, and for tunneling into an interacting one-dimensional system of fermions. It often happens that the finite frequency response of the photon absorption or the tunneling density of states exhibits a singular behavior as a function of frequency: [Formula: see text], where ω(th) is a threshold frequency and α is an exponent characterizing the singular response. In this review singular responses of spin-incoherent Luttinger liquids are reviewed. Such responses most often do not fall into the familiar form above, but instead typically exhibit logarithmic corrections and display a much higher universality in terms of the microscopic interactions in the theory. Specific predictions are made, the current experimental situation is summarized and key outstanding theoretical issues related to spin-incoherent Luttinger liquids are highlighted.
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Affiliation(s)
- Gregory A Fiete
- Department of Physics, University of Texas at Austin, Austin, TX 78712, USA
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17
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Hew WK, Thomas KJ, Pepper M, Farrer I, Anderson D, Jones GAC, Ritchie DA. Incipient formation of an electron lattice in a weakly confined quantum wire. PHYSICAL REVIEW LETTERS 2009; 102:056804. [PMID: 19257536 DOI: 10.1103/physrevlett.102.056804] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2008] [Indexed: 05/25/2023]
Abstract
We study the low-temperature transport properties of 1D quantum wires as the confinement strength V_{conf} and the carrier density n_{1D} are varied using a combination of split gates and a top gate in GaAs/AlGaAs heterostructures. At intermediate V_{conf} and n_{1D}, we observe a jump in conductance to 4e;{2}/h, suggesting a double wire. On further reducing n_{1D}, plateau at 2e;{2}/h returns. Our results show beginnings of the formation of an electron lattice in an interacting quasi-1D quantum wire. In the presence of an in-plane magnetic field, mixing of spin-aligned levels of the two wires gives rise to more complex states.
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Affiliation(s)
- W K Hew
- Cavendish Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
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Meyer JS, Matveev KA. Wigner crystal physics in quantum wires. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:023203. [PMID: 21813970 DOI: 10.1088/0953-8984/21/2/023203] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The physics of interacting quantum wires has attracted a lot of attention recently. When the density of electrons in the wire is very low, the strong repulsion between electrons leads to the formation of a Wigner crystal. We review the rich spin and orbital properties of the Wigner crystal, in both the one-dimensional and the quasi-one-dimensional regimes. In the one-dimensional Wigner crystal the electron spins form an antiferromagnetic Heisenberg chain with exponentially small exchange coupling. In the presence of leads, the resulting inhomogeneity of the electron density causes a violation of spin-charge separation. As a consequence the spin degrees of freedom affect the conductance of the wire. Upon increasing the electron density, the Wigner crystal starts deviating from the strictly one-dimensional geometry, forming a zigzag structure instead. Spin interactions in this regime are dominated by ring exchanges, and the phase diagram of the resulting zigzag spin chain has a number of unpolarized phases as well as regions of complete and partial spin polarization. Finally we address the orbital properties in the vicinity of the transition from a one-dimensional to a quasi-one-dimensional state. Due to the locking between chains in the zigzag Wigner crystal, only one gapless mode exists. Manifestations of Wigner crystal physics at weak interactions are explored by studying the fate of the additional gapped low-energy mode as a function of interaction strength.
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Affiliation(s)
- Julia S Meyer
- Department of Physics, The Ohio State University, Columbus, OH 43210, USA
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