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Fei F, Zhang S, Zhang M, Shah SA, Song F, Wang X, Wang B. The Material Efforts for Quantized Hall Devices Based on Topological Insulators. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1904593. [PMID: 31840308 DOI: 10.1002/adma.201904593] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 09/09/2019] [Indexed: 06/10/2023]
Abstract
A topological insulator (TI) is a kind of novel material hosting a topological band structure and plenty of exotic topological quantum effects. Achieving quantized electrical transport, including the quantum Hall effect (QHE) and the quantum anomalous Hall effect (QAHE), is an important aspect of realizing quantum devices based on TI materials. Intense efforts are made in this field, in which the most essential research is based on the optimization of realistic TI materials. Herein, the TI material development process is reviewed, focusing on the realization of quantized transport. Especially, for QHE, the strategies to increase the surface transport ratio and decrease the threshold magnetic field of QHE are examined. For QAHE, the evolution history of magnetic TIs is introduced, and the recently discovered magnetic TI candidates with intrinsic magnetizations are discussed in detail. Moreover, future research perspectives on these novel topological quantum effects are also evaluated.
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Affiliation(s)
- Fucong Fei
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Shuai Zhang
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Minhao Zhang
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Syed Adil Shah
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Fengqi Song
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Xuefeng Wang
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Baigeng Wang
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
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Dodoo-Amoo NA, Saeed K, Mistry D, Khanna SP, Li L, Linfield EH, Davies AG, Cunningham JE. Non-universality of scaling exponents in quantum Hall transitions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:475801. [PMID: 25351842 DOI: 10.1088/0953-8984/26/47/475801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We have investigated experimentally the scaling behaviour of quantum Hall transitions in GaAs/AlGaAs heterostructures of a range of mobility, carrier concentration, and spacer layer width. All three critical scaling exponents γ, κ and p were determined independently for each sample. We measure the localization length exponent to be γ ≈ 2.3, in good agreement with expected predictions from scaling theory, but κ and p are found to possess non-universal values. Results obtained for κ range from κ = 0.16 ± 0.02 to κ = 0.67 ± 0.02, and are found to be Landau level (LL) dependent, whereas p is found to decrease with increasing sample mobility. Our results demonstrate the existence of two transport regimes in the LL conductivity peak; universality is found within the quantum coherent transport regime present in the tails of the conductivity peak, but is absent within the classical transport regime found close to the critical point at the centre of the conductivity peak. We explain these results using a percolation model and show that the critical scaling exponent depends on certain important length scales that correspond to the microscopic description of electron transport in the bulk of a two-dimensional electron system.
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Affiliation(s)
- N A Dodoo-Amoo
- School of Electronic and Electrical Engineering, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT,UK
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Hashimoto K, Sohrmann C, Wiebe J, Inaoka T, Meier F, Hirayama Y, Römer RA, Wiesendanger R, Morgenstern M. Quantum Hall transition in real space: from localized to extended states. PHYSICAL REVIEW LETTERS 2008; 101:256802. [PMID: 19113737 DOI: 10.1103/physrevlett.101.256802] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2008] [Indexed: 05/27/2023]
Abstract
Using scanning tunneling spectroscopy in an ultrahigh vacuum at low temperature (T=0.3 K) and high magnetic fields (B<or=12 T), we directly probe electronic wave functions across an integer quantum Hall transition. In accordance with theoretical predictions, we observe the evolution from localized drift states in the insulating phases to branched extended drift states at the quantum critical point. The observed microscopic behavior close to the extended state indicates points of localized quantum tunneling, which are considered to be decisive for a quantitative description of the transition.
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Affiliation(s)
- K Hashimoto
- Institute of Applied Physics, Hamburg University, Jungiusstrae 11, D-20355 Hamburg, Germany.
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Xiong G, Wang SD, Niu Q, Wang Y, Xie XC, Tian DC, Wang XR. Possible existence of a band of extended states induced by inter-Landau-band mixing in a quantum Hall system. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2006; 18:2029-2055. [PMID: 21697574 DOI: 10.1088/0953-8984/18/6/017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The mixing of states with opposite chiralities in a quantum Hall system is shown to have a delocalization effect. It is possible that extended states may form bands because of this mixing, as is shown through a numerical calculation on a two-channel network model. Based on this result, a new phase diagram with a narrow metallic phase separating two adjacent QH phases and/or separating a QH phase from the insulating phase is proposed. The data from recent non-scaling experiments are reanalysed and it is shown that they seem to be consistent with the new phase diagram. However, due to finite-size effects, further study on large system size is still needed to conclude whether there are extended state bands in the thermodynamic limit.
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Affiliation(s)
- Gang Xiong
- Physics Department, Beijing Normal University, Beijing 100875, People's Republic of China
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Li W, Csáthy GA, Tsui DC, Pfeiffer LN, West KW. Scaling and universality of integer quantum Hall plateau-to-plateau transitions. PHYSICAL REVIEW LETTERS 2005; 94:206807. [PMID: 16090272 DOI: 10.1103/physrevlett.94.206807] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Indexed: 05/03/2023]
Abstract
We have investigated the integer quantum Hall plateau-to-plateau transition in two-dimensional electrons confined to AlxGa(1-x)As-Al0.33Ga0.67As heterostructures over a broad range of Al concentration x. For x between 0.65% and 1.6%, where the dominant contribution to disorder is from the short-range alloy potential fluctuations, we observe a perfect power-law scaling in the temperature range from 30 mK to 1 K with a critical exponent kappa = 0.42 +/- 0.01.
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Affiliation(s)
- Wanli Li
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
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Ilani S, Martin J, Teitelbaum E, Smet JH, Mahalu D, Umansky V, Yacoby A. The microscopic nature of localization in the quantum Hall effect. Nature 2004; 427:328-32. [PMID: 14737162 DOI: 10.1038/nature02230] [Citation(s) in RCA: 165] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2003] [Accepted: 11/21/2003] [Indexed: 11/09/2022]
Abstract
The quantum Hall effect arises from the interplay between localized and extended states that form when electrons, confined to two dimensions, are subject to a perpendicular magnetic field. The effect involves exact quantization of all the electronic transport properties owing to particle localization. In the conventional theory of the quantum Hall effect, strong-field localization is associated with a single-particle drift motion of electrons along contours of constant disorder potential. Transport experiments that probe the extended states in the transition regions between quantum Hall phases have been used to test both the theory and its implications for quantum Hall phase transitions. Although several experiments on highly disordered samples have affirmed the validity of the single-particle picture, other experiments and some recent theories have found deviations from the predicted universal behaviour. Here we use a scanning single-electron transistor to probe the individual localized states, which we find to be strikingly different from the predictions of single-particle theory. The states are mainly determined by Coulomb interactions, and appear only when quantization of kinetic energy limits the screening ability of electrons. We conclude that the quantum Hall effect has a greater diversity of regimes and phase transitions than predicted by the single-particle framework. Our experiments suggest a unified picture of localization in which the single-particle model is valid only in the limit of strong disorder.
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Affiliation(s)
- S Ilani
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel.
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KALUGIN NG, SAĞOL BE, STELLMACH C, BUß A, HIRSCH A, NACHTWEI G, HEIN G. RELAXATION OSCILLATIONS AND DYNAMICAL PROPERTIES OF A BISTABLE QUANTUM HALL SYSTEM. INTERNATIONAL JOURNAL OF NANOSCIENCE 2003. [DOI: 10.1142/s0219581x0300167x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We present a simple relaxation oscillator based on a quantum Hall device with Corbino geometry near the breakdown of the quantum Hall effect. The amplitude of the observed relaxation oscillations is found many times bigger than one can expect from the hysteresis of the quantum Hall effect breakdown, measured at constant currents. This result is explained by a dynamical suppression of hopping contribution to the conductivity σxx, and corresponding dynamical reduction of localization length ξ.
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Affiliation(s)
- N. G. KALUGIN
- Institut für Technische Physik, TU-Braunschweig, D-38106 Braunschweig, Germany
- Department of Physics, Texas A&M University, College Station, TX 77843-4242, USA
| | - B. E. SAĞOL
- Institut für Technische Physik, TU-Braunschweig, D-38106 Braunschweig, Germany
| | - C. STELLMACH
- Institut für Technische Physik, TU-Braunschweig, D-38106 Braunschweig, Germany
| | - A. BUß
- Institut für Technische Physik, TU-Braunschweig, D-38106 Braunschweig, Germany
| | - A. HIRSCH
- Institut für Technische Physik, TU-Braunschweig, D-38106 Braunschweig, Germany
| | - G. NACHTWEI
- Institut für Technische Physik, TU-Braunschweig, D-38106 Braunschweig, Germany
| | - G. HEIN
- Physikalisch-Technische Bundesanstalt, D-38116 Braunschweig, Germany
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Morgenstern M, Klijn J, Meyer C, Wiesendanger R. Real-space observation of drift States in a two-dimensional electron system at high magnetic fields. PHYSICAL REVIEW LETTERS 2003; 90:056804. [PMID: 12633386 DOI: 10.1103/physrevlett.90.056804] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2002] [Indexed: 05/24/2023]
Abstract
The local density of states of the adsorbate-induced two-dimensional electron system is studied in magnetic fields up to B=6 T. Landau quantization is observed and drift states with a width of about the magnetic length are found in agreement with theoretical predictions. At the tails of the Landau levels the states form closed paths indicating localization. These states show the expected energy dependence. A multifractal analysis applied to the data results in a nice parabolic shape of the characteristic f(alpha) spectra, but we find only a slight displacement of the origin from alpha=2.0 for the states in the center of the Landau level.
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Affiliation(s)
- M Morgenstern
- Institute of Applied Physics, Hamburg University, Jungiusstrasse 11, Germany
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Hohls F, Zeitler U, Haug RJ, Meisels R, Dybko K, Kuchar F. Dynamical scaling of the quantum Hall plateau transition. PHYSICAL REVIEW LETTERS 2002; 89:276801. [PMID: 12513229 DOI: 10.1103/physrevlett.89.276801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2002] [Indexed: 05/24/2023]
Abstract
Using different experimental techniques, we examine the dynamical scaling of the quantum Hall plateau transition in a frequency range f=0.1-55 GHz. We present a scheme that allows for a simultaneous scaling analysis of these experiments and all other data in literature. We observe a universal scaling function with an exponent kappa=0.5+/-0.1, yielding a dynamical exponent z=0.9+/-0.2.
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Affiliation(s)
- F Hohls
- Institut für Festkörperphysik, Universität Hannover, Appelstrasse 2, 30167 Hannover, Germany.
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Avishai Y, Meir Y. New spin-orbit-induced universality class in the integer quantum Hall regime. PHYSICAL REVIEW LETTERS 2002; 89:076602. [PMID: 12190544 DOI: 10.1103/physrevlett.89.076602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2001] [Indexed: 05/23/2023]
Abstract
Using heuristic arguments and numerical simulations it is argued that the critical exponent nu describing the localization length divergence at the integer quantum-Hall transition is modified in the presence of spin-orbit scattering with short-range correlations. The exponent is very close to nu=4/3, the percolation correlation length exponent, consistent with the prediction of a semiclassical argument. In addition, a band of weakly localized states is conjectured.
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Affiliation(s)
- Yshai Avishai
- Department of Physics and Ilse Katz Center for Meso- and Nanoscale Science and Technology, Ben Gurion University, Beer Sheva, Israel
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