1
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Liang X, Shamim S, Chen D, Fürst L, Taniguchi T, Watanabe K, Buhmann H, Kleinlein J, Molenkamp LW. Graphite/h-BN van der Waals heterostructure as a gate stack for HgTe quantum wells. NANOTECHNOLOGY 2024; 35:345001. [PMID: 38788703 DOI: 10.1088/1361-6528/ad501c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Accepted: 05/24/2024] [Indexed: 05/26/2024]
Abstract
Two-dimensional topological insulators have attracted much interest due to their potential applications in spintronics and quantum computing. To access the exotic physical phenomena, a gate electric field is required to tune the Fermi level into the bulk band gap. Hexagonal boron nitride (h-BN) is a promising alternative gate dielectric due to its unique advantages such as flat and charge-free surface. Here we present a h-BN/graphite van der Waals heterostructure as a top gate on HgTe heterostructure-based Hall bar devices. We compare our results to devices with h-BN/Ti/Au and HfO2/Ti/Au gates. Devices with a h-BN/graphite gate show no charge carrier density shift compared to as-grown structures, in contrast to a significant n-type carrier density increase for HfO2/Ti/Au. We attribute this observation mainly to the comparable work function of HgTe and graphite. In addition, devices with h-BN gate dielectric show slightly higher electron mobility compared to HfO2-based devices. Our results demonstrate the compatibility between layered materials transfer and wet-etched structures and provide a strategy to solve the issue of significant shifts of the carrier density in gated HgTe heterostructures.
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Affiliation(s)
- Xianhu Liang
- Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany
- Institute for Topological Insulators, 97074 Würzburg, Germany
| | - Saquib Shamim
- Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany
- Institute for Topological Insulators, 97074 Würzburg, Germany
| | - Dongyun Chen
- Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany
- Institute for Topological Insulators, 97074 Würzburg, Germany
| | - Lena Fürst
- Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany
- Institute for Topological Insulators, 97074 Würzburg, Germany
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Hartmut Buhmann
- Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany
- Institute for Topological Insulators, 97074 Würzburg, Germany
| | - Johannes Kleinlein
- Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany
- Institute for Topological Insulators, 97074 Würzburg, Germany
| | - Laurens W Molenkamp
- Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany
- Institute for Topological Insulators, 97074 Würzburg, Germany
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2
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Rout P, Papadopoulos N, Peñaranda F, Watanabe K, Taniguchi T, Prada E, San-Jose P, Goswami S. Supercurrent mediated by helical edge modes in bilayer graphene. Nat Commun 2024; 15:856. [PMID: 38287003 PMCID: PMC10824753 DOI: 10.1038/s41467-024-44952-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 01/04/2024] [Indexed: 01/31/2024] Open
Abstract
Bilayer graphene encapsulated in tungsten diselenide can host a weak topological phase with pairs of helical edge states. The electrical tunability of this phase makes it an ideal platform to investigate unique topological effects at zero magnetic field, such as topological superconductivity. Here we couple the helical edges of such a heterostructure to a superconductor. The inversion of the bulk gap accompanied by helical states near zero displacement field leads to the suppression of the critical current in a Josephson geometry. Using superconducting quantum interferometry we observe an even-odd effect in the Fraunhofer interference pattern within the inverted gap phase. We show theoretically that this effect is a direct consequence of the emergence of helical modes that connect the two edges of the sample. The absence of such an effect at high displacement field, as well as in bare bilayer graphene junctions, supports this interpretation and demonstrates the topological nature of the inverted gap.
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Affiliation(s)
- Prasanna Rout
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA, Delft, The Netherlands
| | - Nikos Papadopoulos
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA, Delft, The Netherlands
| | - Fernando Peñaranda
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC. Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, 305-0044, Japan
| | - Elsa Prada
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC. Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
| | - Pablo San-Jose
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC. Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain.
| | - Srijit Goswami
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA, Delft, The Netherlands.
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3
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Randle MD, Hosoda M, Deacon RS, Ohtomo M, Zellekens P, Watanabe K, Taniguchi T, Okazaki S, Sasagawa T, Kawaguchi K, Sato S, Ishibashi K. Gate-Defined Josephson Weak-Links in Monolayer WTe 2. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2301683. [PMID: 37358032 DOI: 10.1002/adma.202301683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 06/15/2023] [Indexed: 06/27/2023]
Abstract
Systems combining superconductors with topological insulators offer a platform for the study of Majorana bound states and a possible route to realize fault tolerant topological quantum computation. Among the systems being considered in this field, monolayers of tungsten ditelluride (WTe2 ) have a rare combination of properties. Notably, it has been demonstrated to be a quantum spin Hall insulator (QSHI) and can easily be gated into a superconducting state. Measurements on gate-defined Josephson weak-link devices fabricated using monolayer WTe2 are reported. It is found that consideration of the 2D superconducting leads are critical in the interpretation of magnetic interference in the resulting junctions. The reported fabrication procedures suggest a facile way to produce further devices from this technically challenging material and the results mark the first step toward realizing versatile all-in-one topological Josephson weak-links using monolayer WTe2 .
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Affiliation(s)
- Michael D Randle
- Advanced Device Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Masayuki Hosoda
- Fujitsu Research, Fujitsu Ltd., 10-1 Morinosato-Wakamiya, Atsugi, Kanagawa, 243-0197, Japan
| | - Russell S Deacon
- Advanced Device Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Manabu Ohtomo
- Fujitsu Research, Fujitsu Ltd., 10-1 Morinosato-Wakamiya, Atsugi, Kanagawa, 243-0197, Japan
| | - Patrick Zellekens
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan
| | - Shota Okazaki
- Laboratory for Materials and Structures, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan
| | - Takao Sasagawa
- Laboratory for Materials and Structures, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan
| | - Kenichi Kawaguchi
- Fujitsu Research, Fujitsu Ltd., 10-1 Morinosato-Wakamiya, Atsugi, Kanagawa, 243-0197, Japan
| | - Shintaro Sato
- Fujitsu Research, Fujitsu Ltd., 10-1 Morinosato-Wakamiya, Atsugi, Kanagawa, 243-0197, Japan
| | - Koji Ishibashi
- Advanced Device Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
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4
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Lu B, Ikegaya S, Burset P, Tanaka Y, Nagaosa N. Tunable Josephson Diode Effect on the Surface of Topological Insulators. PHYSICAL REVIEW LETTERS 2023; 131:096001. [PMID: 37721825 DOI: 10.1103/physrevlett.131.096001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 02/27/2023] [Accepted: 08/02/2023] [Indexed: 09/20/2023]
Abstract
The Josephson rectification effect, where the resistance is finite in one direction while zero in the other, has been recently realized experimentally. The resulting Josephson diode has many potential applications on superconducting devices, including quantum computers. Here, we theoretically show that a superconductor-normal metal-superconductor Josephson junction diode on the two-dimensional surface of a topological insulator has large tunability. The magnitude and sign of the diode quality factor strongly depend on the external magnetic field, gate voltage, and the length of the junction. Such rich properties stem from the interplay between different current-phase relations for the multiple transverse transport channels, and can be used for designing realistic superconducting diode devices.
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Affiliation(s)
- Bo Lu
- Center for Joint Quantum Studies, Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, Department of Physics, Tianjin University, Tianjin 300354, China
| | - Satoshi Ikegaya
- Department of Applied Physics, Nagoya University, Nagoya 464-8603, Japan
- Institute for Advanced Research, Nagoya University, Nagoya 464-8601, Japan
| | - Pablo Burset
- Department of Theoretical Condensed Matter Physics, Condensed Matter Physics Center (IFIMAC) and Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Yukio Tanaka
- Department of Applied Physics, Nagoya University, Nagoya 464-8603, Japan
- Research Center for Crystalline Materials Engineering, Nagoya University, Nagoya 464-8603, Japan
| | - Naoto Nagaosa
- Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama 351-0198, Japan
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5
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Ruzhickiy V, Bakurskiy S, Kupriyanov M, Klenov N, Soloviev I, Stolyarov V, Golubov A. Contribution of Processes in SN Electrodes to the Transport Properties of SN-N-NS Josephson Junctions. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:1873. [PMID: 37368303 DOI: 10.3390/nano13121873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 06/08/2023] [Accepted: 06/13/2023] [Indexed: 06/28/2023]
Abstract
In this paper, we present a theoretical study of electronic transport in planar Josephson Superconductor-Normal Metal-Superconductor (SN-N-NS) bridges with arbitrary transparency of the SN interfaces. We formulate and solve the two-dimensional problem of finding the spatial distribution of the supercurrent in the SN electrodes. This allows us to determine the scale of the weak coupling region in the SN-N-NS bridges, i.e., to describe this structure as a serial connection between the Josephson contact and the linear inductance of the current-carrying electrodes. We show that the presence of a two-dimensional spatial current distribution in the SN electrodes leads to a modification of the current-phase relation and the critical current magnitude of the bridges. In particular, the critical current decreases as the overlap area of the SN parts of the electrodes decreases. We show that this is accompanied by a transformation of the SN-N-NS structure from an SNS-type weak link to a double-barrier SINIS contact. In addition, we find the range of interface transparency in order to optimise device performance. The features we have discovered should have a significant impact on the operation of small-scale superconducting electronic devices, and should be taken into account in their design.
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Affiliation(s)
- Vsevolod Ruzhickiy
- Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 119991 Moscow, Russia
- Dukhov All-Russia Research Institute of Automatics, 101000 Moscow, Russia
- National University of Science and Technology MISIS, 119049 Moscow, Russia
| | - Sergey Bakurskiy
- Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 119991 Moscow, Russia
- National University of Science and Technology MISIS, 119049 Moscow, Russia
| | - Mikhail Kupriyanov
- Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 119991 Moscow, Russia
- National University of Science and Technology MISIS, 119049 Moscow, Russia
| | - Nikolay Klenov
- National University of Science and Technology MISIS, 119049 Moscow, Russia
- Faculty of Physics, Moscow State University, 119991 Moscow, Russia
| | - Igor Soloviev
- Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 119991 Moscow, Russia
- National University of Science and Technology MISIS, 119049 Moscow, Russia
| | - Vasily Stolyarov
- Dukhov All-Russia Research Institute of Automatics, 101000 Moscow, Russia
- National University of Science and Technology MISIS, 119049 Moscow, Russia
- Center for Advanced Mesoscience and Nanotechnology, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
| | - Alexander Golubov
- Center for Advanced Mesoscience and Nanotechnology, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
- Faculty of Science and Technology, MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
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6
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Díez-Mérida J, Díez-Carlón A, Yang SY, Xie YM, Gao XJ, Senior J, Watanabe K, Taniguchi T, Lu X, Higginbotham AP, Law KT, Efetov DK. Symmetry-broken Josephson junctions and superconducting diodes in magic-angle twisted bilayer graphene. Nat Commun 2023; 14:2396. [PMID: 37100775 PMCID: PMC10133447 DOI: 10.1038/s41467-023-38005-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 04/06/2023] [Indexed: 04/28/2023] Open
Abstract
The coexistence of gate-tunable superconducting, magnetic and topological orders in magic-angle twisted bilayer graphene provides opportunities for the creation of hybrid Josephson junctions. Here we report the fabrication of gate-defined symmetry-broken Josephson junctions in magic-angle twisted bilayer graphene, where the weak link is gate-tuned close to the correlated insulator state with a moiré filling factor of υ = -2. We observe a phase-shifted and asymmetric Fraunhofer pattern with a pronounced magnetic hysteresis. Our theoretical calculations of the junction weak link-with valley polarization and orbital magnetization-explain most of these unconventional features. The effects persist up to the critical temperature of 3.5 K, with magnetic hysteresis observed below 800 mK. We show how the combination of magnetization and its current-induced magnetization switching allows us to realise a programmable zero-field superconducting diode. Our results represent a major advance towards the creation of future superconducting quantum electronic devices.
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Affiliation(s)
- J Díez-Mérida
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, 08860, Spain
| | - A Díez-Carlón
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, 08860, Spain
| | - S Y Yang
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, 08860, Spain
| | - Y-M Xie
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - X-J Gao
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - J Senior
- IST Austria, Am Campus 1, 3400, Klosterneuburg, Austria
| | - K Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - T Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - X Lu
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, 08860, Spain
| | | | - K T Law
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Dmitri K Efetov
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, 08860, Spain.
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7
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Rößler M, Fan D, Münning F, Legg HF, Bliesener A, Lippertz G, Uday A, Yazdanpanah R, Feng J, Taskin A, Ando Y. Top-Down Fabrication of Bulk-Insulating Topological Insulator Nanowires for Quantum Devices. NANO LETTERS 2023; 23:2846-2853. [PMID: 36976857 DOI: 10.1021/acs.nanolett.3c00169] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
In a nanowire (NW) of a three-dimensional topological insulator (TI), the quantum confinement of topological surface states leads to a peculiar sub-band structure that is useful for generating Majorana bound states. Top-down fabrication of TINWs from a high-quality thin film would be a scalable technology with great design flexibility, but there has been no report on top-down-fabricated TINWs where the chemical potential can be tuned to the charge neutrality point (CNP). Here we present a top-down fabrication process for bulk-insulating TINWs etched from high-quality (Bi1-xSbx)2Te3 thin films without degradation. We show that the chemical potential can be gate-tuned to the CNP, and the resistance of the NW presents characteristic oscillations as functions of the gate voltage and the parallel magnetic field, manifesting the TI-sub-band physics. We further demonstrate the superconducting proximity effect in these TINWs, preparing the groundwork for future devices to investigate Majorana bound states.
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Affiliation(s)
- Matthias Rößler
- University of Cologne, Physics Institute II, Zülpicher Str. 77, 50937 Köln, Germany
| | - Dingxun Fan
- University of Cologne, Physics Institute II, Zülpicher Str. 77, 50937 Köln, Germany
| | - Felix Münning
- University of Cologne, Physics Institute II, Zülpicher Str. 77, 50937 Köln, Germany
| | - Henry F Legg
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Andrea Bliesener
- University of Cologne, Physics Institute II, Zülpicher Str. 77, 50937 Köln, Germany
| | - Gertjan Lippertz
- University of Cologne, Physics Institute II, Zülpicher Str. 77, 50937 Köln, Germany
- KU Leuven, Quantum Solid State Physics, Celestijnenlaan 200 D, 3001 Leuven, Belgium
| | - Anjana Uday
- University of Cologne, Physics Institute II, Zülpicher Str. 77, 50937 Köln, Germany
| | - Roozbeh Yazdanpanah
- University of Cologne, Physics Institute II, Zülpicher Str. 77, 50937 Köln, Germany
| | - Junya Feng
- University of Cologne, Physics Institute II, Zülpicher Str. 77, 50937 Köln, Germany
| | - Alexey Taskin
- University of Cologne, Physics Institute II, Zülpicher Str. 77, 50937 Köln, Germany
| | - Yoichi Ando
- University of Cologne, Physics Institute II, Zülpicher Str. 77, 50937 Köln, Germany
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8
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Elfeky B, Cuozzo JJ, Lotfizadeh N, Schiela WF, Farzaneh SM, Strickland WM, Langone D, Rossi E, Shabani J. Evolution of 4π-Periodic Supercurrent in the Presence of an In-Plane Magnetic Field. ACS NANO 2023; 17:4650-4658. [PMID: 36800544 PMCID: PMC10018771 DOI: 10.1021/acsnano.2c10880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 02/15/2023] [Indexed: 06/18/2023]
Abstract
In the presence of a 4π-periodic contribution to the current phase relation, for example in topological Josephson junctions, odd Shapiro steps are expected to be missing. While missing odd Shapiro steps have been observed in several material systems and interpreted in the context of topological superconductivity, they have also been observed in topologically trivial junctions. Here, we study the evolution of such trivial missing odd Shapiro steps in Al-InAs junctions in the presence of an in-plane magnetic field Bθ. We find that the odd steps reappear at a crossover Bθ value, exhibiting an in-plane field angle anisotropy that depends on spin-orbit coupling effects. We interpret this behavior by theoretically analyzing the Andreev bound state spectrum and the transitions induced by the nonadiabatic dynamics of the junction and attribute the observed anisotropy to mode-to-mode coupling. Our results highlight the complex phenomenology of missing Shapiro steps and the underlying current phase relations in planar Josephson junctions designed to realize Majorana states.
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Affiliation(s)
- Bassel
Heiba Elfeky
- Center
for Quantum Information Physics, Department of Physics, New York University, New York, New York 10003, United States
| | - Joseph J. Cuozzo
- Department
of Physics, William & Mary, Williamsburg, Virginia 23187, United States
| | - Neda Lotfizadeh
- Center
for Quantum Information Physics, Department of Physics, New York University, New York, New York 10003, United States
| | - William F. Schiela
- Center
for Quantum Information Physics, Department of Physics, New York University, New York, New York 10003, United States
| | - Seyed M. Farzaneh
- Center
for Quantum Information Physics, Department of Physics, New York University, New York, New York 10003, United States
| | - William M. Strickland
- Center
for Quantum Information Physics, Department of Physics, New York University, New York, New York 10003, United States
| | - Dylan Langone
- Center
for Quantum Information Physics, Department of Physics, New York University, New York, New York 10003, United States
| | - Enrico Rossi
- Department
of Physics, William & Mary, Williamsburg, Virginia 23187, United States
| | - Javad Shabani
- Center
for Quantum Information Physics, Department of Physics, New York University, New York, New York 10003, United States
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9
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Trahms M, Melischek L, Steiner JF, Mahendru B, Tamir I, Bogdanoff N, Peters O, Reecht G, Winkelmann CB, von Oppen F, Franke KJ. Diode effect in Josephson junctions with a single magnetic atom. Nature 2023; 615:628-633. [PMID: 36890238 PMCID: PMC10033399 DOI: 10.1038/s41586-023-05743-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 01/18/2023] [Indexed: 03/10/2023]
Abstract
Current flow in electronic devices can be asymmetric with bias direction, a phenomenon underlying the utility of diodes1 and known as non-reciprocal charge transport2. The promise of dissipationless electronics has recently stimulated the quest for superconducting diodes, and non-reciprocal superconducting devices have been realized in various non-centrosymmetric systems3-10. Here we investigate the ultimate limits of miniaturization by creating atomic-scale Pb-Pb Josephson junctions in a scanning tunnelling microscope. Pristine junctions stabilized by a single Pb atom exhibit hysteretic behaviour, confirming the high quality of the junctions, but no asymmetry between the bias directions. Non-reciprocal supercurrents emerge when inserting a single magnetic atom into the junction, with the preferred direction depending on the atomic species. Aided by theoretical modelling, we trace the non-reciprocity to quasiparticle currents flowing by means of electron-hole asymmetric Yu-Shiba-Rusinov states inside the superconducting energy gap and identify a new mechanism for diode behaviour in Josephson junctions. Our results open new avenues for creating atomic-scale Josephson diodes and tuning their properties through single-atom manipulation.
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Affiliation(s)
- Martina Trahms
- Fachbereich Physik, Freie Universität Berlin, Berlin, Germany
| | - Larissa Melischek
- Dahlem Center for Complex Quantum Systems, Fachbereich Physik, Freie Universität Berlin, Berlin, Germany
| | - Jacob F Steiner
- Dahlem Center for Complex Quantum Systems, Fachbereich Physik, Freie Universität Berlin, Berlin, Germany
| | - Bharti Mahendru
- Fachbereich Physik, Freie Universität Berlin, Berlin, Germany
| | - Idan Tamir
- Fachbereich Physik, Freie Universität Berlin, Berlin, Germany
| | - Nils Bogdanoff
- Fachbereich Physik, Freie Universität Berlin, Berlin, Germany
| | - Olof Peters
- Fachbereich Physik, Freie Universität Berlin, Berlin, Germany
| | - Gaël Reecht
- Fachbereich Physik, Freie Universität Berlin, Berlin, Germany
| | | | - Felix von Oppen
- Dahlem Center for Complex Quantum Systems, Fachbereich Physik, Freie Universität Berlin, Berlin, Germany
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10
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Zou WK, Wang Q, Zhao HK. Dynamic heat and charge transports through double-quantum-dot-interferometer modulated by Majorana bound states and time-oscillating Aharonov-Bohm flux. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 35:165303. [PMID: 36796103 DOI: 10.1088/1361-648x/acbcb9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 02/16/2023] [Indexed: 06/18/2023]
Abstract
Dynamic properties of Majorana bound states (MBSs) coupled double-quantum-dot (DQD) interferometer threaded with ac magnetic flux are investigated, and the time-averaged thermal current formulas are derived. Photon-assisted local and nonlocal Andreev reflections contribute efficiently to the charge and heat transports. The modifications of source-drain electric, electric-thermal, thermal conductances (G,ξ,κe), Seebeck coefficient (Sc), and thermoelectric figure of merit (ZT) versus AB phase have been calculated numerically. These coefficients exhibit the shift of oscillation period from 2πto 4πdistinctly due to attaching MBSs. The applied ac flux enhances the magnitudes ofG,ξ,κeobviously, and the detailed enhancing behaviors are relevant to the energy levels of DQD. The enhancements ofScandZTare generated due to the coupling of MBSs, while the application of ac flux suppresses the resonant oscillations. The investigation provides a clue for detecting MBSs through measuring the photon-assistedScandZTversus AB phase oscillations.
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Affiliation(s)
- Wei-Ke Zou
- School of Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China
- School of Physics and New Energy, Xuzhou University of Technology, Xuzhou 221018, People's Republic of China
| | - Qing Wang
- School of Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Hong-Kang Zhao
- School of Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China
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11
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Vigliotti L, Calzona A, Traverso Ziani N, Bergeret FS, Sassetti M, Trauzettel B. Effects of the Spatial Extension of the Edge Channels on the Interference Pattern of a Helical Josephson Junction. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:569. [PMID: 36770530 PMCID: PMC9920926 DOI: 10.3390/nano13030569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 01/25/2023] [Accepted: 01/29/2023] [Indexed: 06/18/2023]
Abstract
Josephson junctions (JJs) in the presence of a magnetic field exhibit qualitatively different interference patterns depending on the spatial distribution of the supercurrent through the junction. In JJs based on two-dimensional topological insulators (2DTIs), the electrons/holes forming a Cooper pair (CP) can either propagate along the same edge or be split into the two edges. The former leads to a SQUID-like interference pattern, with the superconducting flux quantum ϕ0 (where ϕ0=h/2e) as a fundamental period. If CPs' splitting is additionally included, the resultant periodicity doubles. Since the edge states are typically considered to be strongly localized, the critical current does not decay as a function of the magnetic field. The present paper goes beyond this approach and inspects a topological JJ in the tunneling regime featuring extended edge states. It is here considered the possibility that the two electrons of a CP propagate and explore the junction independently over length scales comparable to the superconducting coherence length. As a consequence of the spatial extension, a decaying pattern with different possible periods is obtained. In particular, it is shown that, if crossed Andreev reflections (CARs) are dominant and the edge states overlap, the resulting interference pattern features oscillations whose periodicity approaches 2ϕ0.
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Affiliation(s)
- Lucia Vigliotti
- Dipartimento di Fisica, Università degli Studi di Genova, Via Dodecaneso 33, 16146 Genova, Italy
| | - Alessio Calzona
- Institute for Theoretical Physics and Astrophysics, University of Würzburg, D-97074 Würzburg, Germany
| | - Niccolò Traverso Ziani
- Dipartimento di Fisica, Università degli Studi di Genova, Via Dodecaneso 33, 16146 Genova, Italy
- CNR-SPIN, Via Dodecaneso 33, 16146 Genova, Italy
| | - F. Sebastian Bergeret
- Centro de Física de Materiales (CFM-MPC), Centro Mixto CSIC-UPV/EHU, E-20018 Donostia-San Sebastián, Spain
- Donostia International Physics Center (DIPC), E-20018 Donostia-San Sebastián, Spain
| | - Maura Sassetti
- Dipartimento di Fisica, Università degli Studi di Genova, Via Dodecaneso 33, 16146 Genova, Italy
- CNR-SPIN, Via Dodecaneso 33, 16146 Genova, Italy
| | - Björn Trauzettel
- Institute for Theoretical Physics and Astrophysics, University of Würzburg, D-97074 Würzburg, Germany
- Würzburg-Dresden Cluster of Excellence ct.qmat, D-97074 Würzburg, Germany
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12
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Wang Z, Feng JJ, Huang Z, Niu Q. Transport Theory for Topological Josephson Junctions with a Majorana Qubit. PHYSICAL REVIEW LETTERS 2022; 129:257001. [PMID: 36608237 DOI: 10.1103/physrevlett.129.257001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 11/15/2022] [Indexed: 06/17/2023]
Abstract
We construct a semiclassical theory for the transport of topological Josephson junctions starting from a microscopic Hamiltonian that comprehensively includes the interplay among the Majorana qubit, the Josephson phase, and the dissipation process. With the path integral approach, we derive a set of semiclassical equations of motion that can be used to calculate the time evolution of the Josephson phase and the Majorana qubit. In the equations we reveal rich dynamical phenomena such as the qubit-induced charge pumping, the effective spin-orbit torque, and the Gilbert damping. We demonstrate the influence of these dynamical phenomena on the transport signatures of the junction. We apply the theory to study the Shapiro steps of the junction, and find the suppression of the first Shapiro step due to the dynamical feedback of the Majorana qubit.
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Affiliation(s)
- Zhi Wang
- School of Physics, Sun Yat-sen University, Guangzhou 510275, China
- Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, Sun Yat-sen University, Guangzhou 510275, China
| | - Jia-Jin Feng
- International Center for Quantum Materials, Peking University, Beijing 100871, China
| | - Zhao Huang
- Texas Center for Superconductivity, University of Houston, Houston, Texas 77204, USA
| | - Qian Niu
- School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China
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13
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Liu L, Sun S, Huo Y, Li S, Han T. Current through a hybrid four-terminal Josephson junction with Majorana nanowires. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:395302. [PMID: 35835089 DOI: 10.1088/1361-648x/ac8131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Accepted: 07/14/2022] [Indexed: 06/15/2023]
Abstract
We investigate the current through a hybrid four-terminal Josephson junction with semiconductor nanowires, in which the junction is connected with two superconducting electrodes and two normal electrodes. The semiconductor nanowire, which is subject to an external magnetic field with Rashba spin-orbit coupling and proximity-induced superconductivity, can host Majorana bound states. When all the nanowires lie in topological nontrivial region, a 4π-periodic current can be observed through the normal terminal and a 2π-periodic current through the superconducting terminal. When a rotating magnetic field is applied to the junction, the supercurrent through different terminals varies with the variation of the magnetic field direction. Only when the magnetic field is applied at certain angles, we find that the 4π-periodic current will appear through the normal terminal.
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Affiliation(s)
- Long Liu
- Hebei College of Industry and Technology, Shijiazhuang, Hebei, 050091, People's Republic of China
| | - Sutao Sun
- School of Mathmatics and Science, Hebei GEO University, Shijiazhuang 050031, People's Republic of China
| | - Yunchang Huo
- Hebei College of Industry and Technology, Shijiazhuang, Hebei, 050091, People's Republic of China
| | - Shuang Li
- Hebei College of Industry and Technology, Shijiazhuang, Hebei, 050091, People's Republic of China
| | - Tiwen Han
- Hebei College of Industry and Technology, Shijiazhuang, Hebei, 050091, People's Republic of China
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14
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Shekhar P, Shamim S, Hartinger S, Schlereth R, Hock V, Buhmann H, Kleinlein J, Molenkamp LW. Low-Temperature Atomic Layer Deposition of Hafnium Oxide for Gating Applications. ACS APPLIED MATERIALS & INTERFACES 2022; 14:33960-33967. [PMID: 35820660 DOI: 10.1021/acsami.2c06176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We present a novel low-temperature (30 °C) atomic layer deposition process for hafnium oxide and apply the layers as gate dielectric to fabricate devices out of the thermally sensitive topological insulator HgTe. The key to achieving self-limiting growth at these low temperatures is the incorporation of sufficiently long purge times ( ≥150 s) in the deposition cycles. We investigate the structural and compositional properties of these thin films using X-ray reflectometry and photoelectron spectroscopy, finding a growth rate of 1.6 Å per cycle and an atomic ratio of Hf/O of 1:1.85. In addition, we report on the transport properties of the microstructured devices, which are much enhanced compared to previous device generations. We determine a relative permittivity of ∼15 for our HfO2 layers. Our process considerably reduces the thermal load of the samples during microfabrication and can be adapted to a broad range of materials, enabling the fabrication of high-quality gate insulators on various temperature-sensitive materials.
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Affiliation(s)
- Pragya Shekhar
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, 97074 Würzburg, Germany
| | - Saquib Shamim
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, 97074 Würzburg, Germany
| | - Simon Hartinger
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, 97074 Würzburg, Germany
| | - Raimund Schlereth
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, 97074 Würzburg, Germany
| | - Volkmar Hock
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, 97074 Würzburg, Germany
| | - Hartmut Buhmann
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, 97074 Würzburg, Germany
| | - Johannes Kleinlein
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, 97074 Würzburg, Germany
| | - Laurens W Molenkamp
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, 97074 Würzburg, Germany
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15
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Davydova M, Prembabu S, Fu L. Universal Josephson diode effect. SCIENCE ADVANCES 2022; 8:eabo0309. [PMID: 35675396 PMCID: PMC9176746 DOI: 10.1126/sciadv.abo0309] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Accepted: 04/19/2022] [Indexed: 05/27/2023]
Abstract
We propose a universal mechanism for the Josephson diode effect in short Josephson junctions. The proposed mechanism is due to finite Cooper pair momentum and is a manifestation of simultaneous breaking of inversion and time-reversal symmetries. The diode efficiency is up to 40%, which corresponds to an asymmetry between the critical currents in opposite directions Ic+/Ic- ≈ 230%. We show that this arises from both the Doppler shift of the Andreev bound state energies and the phase-independent asymmetric current from the continuum. Last, we propose a simple scheme for achieving finite-momentum pairing, which does not rely on spin-orbit coupling and thus greatly expands existing platforms for the observation of supercurrent diode effects.
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Affiliation(s)
- Margarita Davydova
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Saranesh Prembabu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Liang Fu
- Corresponding author. (M.D.); (L.F.)
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16
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Lu B, Zhang Y. Tunable Majorana corner modes by orbital-dependent exchange interaction in a two-dimensional topological superconductor. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:305302. [PMID: 35580592 DOI: 10.1088/1361-648x/ac709e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 05/17/2022] [Indexed: 06/15/2023]
Abstract
We theoretically study the effect of orbital-dependent exchange field in the formation of second order topological superconductors. We demonstrate that changing the orbital difference can induce topological transition and the Majorana corner modes therein can be manipulated. We further propose to detect the corner modes via a normal probe terminal. The conductance quantization is found to be robust to changes of the relevant system parameters.
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Affiliation(s)
- Bo Lu
- Center for Joint Quantum Studies and Department of Physics, Tianjin University, Tianjin 300072, People's Republic of China
| | - Yiying Zhang
- Center for Joint Quantum Studies and Department of Physics, Tianjin University, Tianjin 300072, People's Republic of China
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17
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Abstract
Our work shows a fascinating application of finite-momentum superconductivity, the supercurrent diode effect, which is being reported in a growing number of experiments. We show that, under external magnetic field, Cooper pairs can acquire finite momentum so that critical currents in the direction parallel and antiparallel to the Cooper pair momentum become unequal. When both inversion and time-reversal symmetries are broken, the critical current of a superconductor can be nonreciprocal. In this work, we show that, in certain classes of two-dimensional superconductors with antisymmetric spin–orbit coupling, Cooper pairs acquire a finite momentum upon the application of an in-plane magnetic field, and, as a result, critical currents in the direction parallel and antiparallel to the Cooper pair momentum become unequal. This supercurrent diode effect is also manifested in the polarity dependence of in-plane critical fields induced by a supercurrent. These nonreciprocal effects may be found in polar SrTiO3 film, few-layer MoTe2 in the Td phase, and twisted bilayer graphene in which the valley degree of freedom plays a role analogous to spin.
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18
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Frombach D, Recher P. Tunable effective length of fractional Josephson junctions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:164005. [PMID: 35062004 DOI: 10.1088/1361-648x/ac4dbc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 01/21/2022] [Indexed: 06/14/2023]
Abstract
Topological Josephson junctions (TJJs) have been a subject of widespread interest due to their hosting of Majorana zero modes. In long junctions, i.e. junctions where the junction length exceeds the superconducting coherence length, TJJs manifest themselves in specific features of the critical current (Beenakker 2013Phys. Rev. Lett.110017003). Here we propose to couple the helical edge states mediating the TJJ to additional channels or quantum dots, by which the effective junction length can be increased by tunable parameters associated with these couplings, so that such measurements become possible even in short junctions. Besides effective low-energy models that we treat analytically, we investigate realizations by a Kane-Mele model with edge passivation and treat them numerically via tight binding models. In each case, we explicitly calculate the critical current using the Andreev bound state spectrum and show that it differs in effectively long junctions in the cases of strong and weak parity changing perturbations (quasiparticle poisoning).
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Affiliation(s)
- Daniel Frombach
- Institut für Mathematische Physik, Technische Universität Braunschweig, D-38106 Braunschweig, Germany
| | - Patrik Recher
- Institut für Mathematische Physik, Technische Universität Braunschweig, D-38106 Braunschweig, Germany
- Laboratory for Emerging Nanometrology Braunschweig, D-38106 Braunschweig, Germany
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19
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Ngabonziza P. Quantum transport and potential of topological states for thermoelectricity in Bi 2Te 3thin films. NANOTECHNOLOGY 2022; 33:192001. [PMID: 35081521 DOI: 10.1088/1361-6528/ac4f17] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 01/26/2022] [Indexed: 06/14/2023]
Abstract
This paper reviews recent developments in quantum transport and it presents current efforts to explore the contribution of topological insulator boundary states to thermoelectricity in Bi2Te3thin films. Although Bi2Te3has been used as a thermoelectric material for many years, it is only recently that thin films of this material have been synthesized as 3D topological insulators with interesting physics and potential applications related to topologically protected surface states. A major bottleneck in Bi2Te3thin films has been eliminating its bulk conductivity while increasing its crystal quality. The ability to grow epitaxial films with high crystal quality and to fabricate sophisticated Bi2Te3-based devices is attractive for implementing a variety of topological quantum devices and exploring the potential of topological states to improve thermoelectric properties. Special emphasis is laid on preparing low-defect-density Bi2Te3epitaxial films, gate-tuning of normal-state transport and Josephson supercurrent in topological insulator/superconductor hybrid devices. Prospective quantum transport experiments on Bi2Te3thin-film devices are discussed as well. Finally, an overview of current progress on the contribution of topological insulator boundary states to thermoelectricity is presented. Future explorations to reveal the potential of topological states for improving thermoelectric properties of Bi2Te3films and realizing high-performance thermoelectric devices are discussed.
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Affiliation(s)
- Prosper Ngabonziza
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany
- Department of Physics, University of Johannesburg, PO Box 524, Auckland Park 2006, Johannesburg, South Africa
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20
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Wang J, Powers W, Zhang Z, Smith M, McIntosh BJ, Bac SK, Riney L, Zhukovskyi M, Orlova T, Rokhinson LP, Hsu YT, Liu X, Assaf BA. Observation of Coexisting Weak Localization and Superconducting Fluctuations in Strained Sn 1-xIn xTe Thin Films. NANO LETTERS 2022; 22:792-800. [PMID: 35007089 DOI: 10.1021/acs.nanolett.1c04370] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Topological superconductors have attracted tremendous excitement as they are predicted to host Majorana zero modes that can be utilized for topological quantum computing. Candidate topological superconductor Sn1-xInxTe thin films (0 < x < 0.3) grown by molecular beam epitaxy and strained in the (111) plane are shown to host quantum interference effects in the conductivity coexisting with superconducting fluctuations above the critical temperature Tc. An analysis of the normal state magnetoresistance reveals these effects. A crossover from weak antilocalization to localization is consistently observed in superconducting samples, indicating that superconductivity originates dominantly from charge carriers occupying trivial states that may be strongly spin-orbit split. A large enhancement of the conductivity is observed above Tc, indicating the presence of superconducting fluctuations. Our results motivate a re-examination of the debated pairing symmetry of this material when subjected to quantum confinement and lattice strain.
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Affiliation(s)
- Jiashu Wang
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - William Powers
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Zhan Zhang
- X-ray Science Division, Advanced Photon Source, Argonne National Lab, Lemont, Illinois 60439, United States
| | - Michael Smith
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Bradlee J McIntosh
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Seul Ki Bac
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Logan Riney
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Maksym Zhukovskyi
- Notre Dame Integrated Imaging Facility, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Tatyana Orlova
- Notre Dame Integrated Imaging Facility, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Leonid P Rokhinson
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
- Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Yi-Ting Hsu
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Xinyu Liu
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Badih A Assaf
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
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21
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Wang D, Telford EJ, Benyamini A, Jesudasan J, Raychaudhuri P, Watanabe K, Taniguchi T, Hone J, Dean CR, Pasupathy AN. Andreev Reflections in NbN/Graphene Junctions under Large Magnetic Fields. NANO LETTERS 2021; 21:8229-8235. [PMID: 34569787 DOI: 10.1021/acs.nanolett.1c02020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Hybrid superconductor/graphene (SC/g) junctions are excellent candidates for investigating correlations between Cooper pairs and quantum Hall (QH) edge modes. Experimental studies are challenging as Andreev reflections are extremely sensitive to junction disorder, and high magnetic fields are required to form QH edge states. We fabricated low-resistance SC/g interfaces, composed of graphene edge contacted with NbN with a barrier strength of Z ≈ 0.4, that remain superconducting under magnetic fields larger than 18 T. We establish the role of graphene's Dirac band structure on zero-field Andreev reflections and demonstrate dynamic tunability of the Andreev reflection spectrum by moving the boundary between specular and retro Andreev reflections with parallel magnetic fields. Through the application of perpendicular magnetic fields, we observe an oscillatory suppression of the 2-probe conductance in the ν = 4 Landau level attributed to the reduced efficiency of Andreev processes at the NbN/g interface, consistent with theoretical predictions.
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Affiliation(s)
- Da Wang
- Department of Physics, Columbia University, New York, New York 10027, United States
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Evan J Telford
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Avishai Benyamini
- Department of Physics, Columbia University, New York, New York 10027, United States
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - John Jesudasan
- Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
| | - Pratap Raychaudhuri
- Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Cory R Dean
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, New York 10027, United States
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States
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22
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Kuang W, Lopez-Polin G, Lee H, Guinea F, Whitehead G, Timokhin I, Berdyugin AI, Kumar RK, Yazyev OV, Walet N, Principi A, Geim AK, Grigorieva IV. Magnetization Signature of Topological Surface States in a Non-Symmorphic Superconductor. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2103257. [PMID: 34365697 DOI: 10.1002/adma.202103257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 06/16/2021] [Indexed: 06/13/2023]
Abstract
Superconductors with nontrivial band structure topology represent a class of materials with unconventional and potentially useful properties. Recent years have seen much success in creating artificial hybrid structures exhibiting the main characteristics of 2D topological superconductors. Yet, bulk materials known to combine inherent superconductivity with nontrivial topology remain scarce, largely because distinguishing their central characteristic-the topological surface states-has proved challenging due to a dominant contribution from the superconducting bulk. In this work, a highly anomalous behavior of surface superconductivity in topologically nontrivial 3D superconductor In2 Bi, where the surface states result from its nontrivial band structure, itself a consequence of the non-symmorphic crystal symmetry and strong spin-orbit coupling, is reported. In contrast to smoothly decreasing diamagnetic susceptibility above the bulk critical field, Hc2 , as seen in conventional superconductors, a near-perfect, Meissner-like screening of low-frequency magnetic fields well above Hc2 is observed. The enhanced diamagnetism disappears at a new phase transition close to the critical field of surface superconductivity, Hc3 . Using theoretical modeling, the anomalous screening is shown to be consistent with modification of surface superconductivity by the topological surface states. The possibility of detecting signatures of the surface states using macroscopic magnetization provides a new tool for the discovery and identification of topological superconductors.
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Affiliation(s)
- Wenjun Kuang
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - Guillermo Lopez-Polin
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - Hyungjun Lee
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, CH-1015, Switzerland
| | - Francisco Guinea
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - George Whitehead
- Department of Chemistry, University of Manchester, Manchester, M13 9PL, UK
| | - Ivan Timokhin
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - Alexey I Berdyugin
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - Roshan Krishna Kumar
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - Oleg V Yazyev
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, CH-1015, Switzerland
| | - Niels Walet
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - Alessandro Principi
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - Andre K Geim
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
- National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
| | - Irina V Grigorieva
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
- National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
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23
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Beach A, Reig-I-Plessis D, MacDougall G, Mason N. Asymmetric Fraunhofer spectra in a topological insulator-based Josephson junction. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:425601. [PMID: 34280900 DOI: 10.1088/1361-648x/ac15d7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Accepted: 07/19/2021] [Indexed: 06/13/2023]
Abstract
Josephson junctions with topological insulators as their weak link (S-TI-S junctions) are predicted to host Majorana fermions, which are key to creating qubits for topologically protected quantum computing. But the details of the S-TI-S current-phase relation and its interplay with magnetic fields are not well understood. We fabricate a Bi2Se3junction with NbTi leads and measure the Fraunhofer patterns of the junction with applied in-plane fields. We observe that asymmetric Fraunhofer patterns appear in the resistance maps ofBzvsBx,y, with aperiodic node spacings. These asymmetric patterns appear even at zero parallel field and for temperatures up to 1 K. The anomalous features are compared to asymmetric Fraunhofer patterns expected for finite Cooper pair momentum shifts as well as geometric effects. We show that the geometric effects can dominate, independent of in-plane field magnitude. These results are important for differentiating geometrical phase shifts from those caused by Cooper pair momentum shifting, Majorana mode signatures, or other unconventional superconducting behavior.
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Affiliation(s)
- Alexander Beach
- Department of Physics and Materials Research Laboratory, University of Illinois, Urbana, 61801 IL, United States of America
| | - Dalmau Reig-I-Plessis
- Department of Physics and Materials Research Laboratory, University of Illinois, Urbana, 61801 IL, United States of America
| | - Gregory MacDougall
- Department of Physics and Materials Research Laboratory, University of Illinois, Urbana, 61801 IL, United States of America
| | - Nadya Mason
- Department of Physics and Materials Research Laboratory, University of Illinois, Urbana, 61801 IL, United States of America
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24
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de Vries FK, Portolés E, Zheng G, Taniguchi T, Watanabe K, Ihn T, Ensslin K, Rickhaus P. Gate-defined Josephson junctions in magic-angle twisted bilayer graphene. NATURE NANOTECHNOLOGY 2021; 16:760-763. [PMID: 33941917 DOI: 10.1038/s41565-021-00896-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 03/10/2021] [Indexed: 05/12/2023]
Abstract
In situ electrostatic control of two-dimensional superconductivity1 is commonly limited due to large charge carrier densities, and gate-defined Josephson junctions are therefore rare2,3. Magic-angle twisted bilayer graphene (MATBG)4-8 has recently emerged as a versatile platform that combines metallic, superconducting, magnetic and insulating phases in a single crystal9-14. Although MATBG appears to be an ideal two-dimensional platform for gate-tunable superconductivity9,11,13, progress towards practical implementations has been hindered by the need for well-defined gated regions. Here we use multilayer gate technology to create a device based on two distinct phases in adjustable regions of MATBG. We electrostatically define the superconducting and insulating regions of a Josephson junction and observe tunable d.c. and a.c. Josephson effects15,16. The ability to tune the superconducting state within a single material circumvents interface and fabrication challenges, which are common in multimaterial nanostructures. This work is an initial step towards devices where gate-defined correlated states are connected in single-crystal nanostructures. We envision applications in superconducting electronics17,18 and quantum information technology19,20.
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Affiliation(s)
| | - Elías Portolés
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
| | - Giulia Zheng
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
| | - Peter Rickhaus
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland.
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25
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Rosenbach D, Schmitt TW, Schüffelgen P, Stehno MP, Li C, Schleenvoigt M, Jalil AR, Mussler G, Neumann E, Trellenkamp S, Golubov AA, Brinkman A, Grützmacher D, Schäpers T. Reappearance of first Shapiro step in narrow topological Josephson junctions. SCIENCE ADVANCES 2021; 7:7/26/eabf1854. [PMID: 34162537 PMCID: PMC8221618 DOI: 10.1126/sciadv.abf1854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 05/12/2021] [Indexed: 06/13/2023]
Abstract
In Josephson junctions, a supercurrent across a nonsuperconducting weak link is carried by electron-hole bound states. Because of the helical spin texture of nondegenerate topological surface states, gapless bound states are established in junctions with topological weak link. These have a characteristic 4π-periodic current phase relation (CΦR) that leads to twice the conventional Shapiro step separation voltage in radio frequency-dependent measurements. In this context, we identify an attenuated first Shapiro step in (Bi0.06Sb0.94)2Te3 (BST) Josephson junctions with AlO x capping layer. We further investigate junctions on narrow, selectively deposited BST nanoribbons, where surface charges are confined to the perimeter of the nanoribbon. Within these junctions, previously identified signatures of gapless bound states are absent. Because of confinement, transverse momentum sub-bands are quantized and a topological gap opening is observed. Surface states within these quantized sub-bands are spin degenerate, which evokes bound states of conventional 2π-periodic CΦR within the BST nanoribbon weak link.
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Affiliation(s)
- Daniel Rosenbach
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany.
- Helmholtz Virtual Institute for Topological Insulators (VITI), Forschungszentrum Jülich, 52425 Jülich, Germany
- JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance, Forschungszentrum Jülich and RWTH Aachen University, Aachen, Germany
| | - Tobias W Schmitt
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
- JARA-FIT Institute Green IT, RWTH Aachen University, 52062 Aachen, Germany
| | - Peter Schüffelgen
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
- Helmholtz Virtual Institute for Topological Insulators (VITI), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Martin P Stehno
- Physikalisches Institut EP3, University of Würzburg, Am Hubland 97070, Würzburg, Germany
| | - Chuan Li
- MESA+ Institute for Nanotechnology, University of Twente, 7500AE Enschede, The Netherlands
| | - Michael Schleenvoigt
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Abdur R Jalil
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Gregor Mussler
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
- Helmholtz Virtual Institute for Topological Insulators (VITI), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Elmar Neumann
- Helmholtz Nano Facility (HNF), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Stefan Trellenkamp
- Helmholtz Nano Facility (HNF), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Alexander A Golubov
- MESA+ Institute for Nanotechnology, University of Twente, 7500AE Enschede, The Netherlands
| | - Alexander Brinkman
- MESA+ Institute for Nanotechnology, University of Twente, 7500AE Enschede, The Netherlands
| | - Detlev Grützmacher
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
- Helmholtz Virtual Institute for Topological Insulators (VITI), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Thomas Schäpers
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
- Helmholtz Virtual Institute for Topological Insulators (VITI), Forschungszentrum Jülich, 52425 Jülich, Germany
- JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance, Forschungszentrum Jülich and RWTH Aachen University, Aachen, Germany
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26
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Lodge MS, Yang SA, Mukherjee S, Weber B. Atomically Thin Quantum Spin Hall Insulators. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2008029. [PMID: 33893669 DOI: 10.1002/adma.202008029] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Revised: 01/12/2021] [Indexed: 06/12/2023]
Abstract
Atomically thin topological materials are attracting growing attention for their potential to radically transform classical and quantum electronic device concepts. Among them is the quantum spin Hall (QSH) insulator-a 2D state of matter that arises from interplay of topological band inversion and strong spin-orbit coupling, with large tunable bulk bandgaps up to 800 meV and gapless, 1D edge states. Reviewing recent advances in materials science and engineering alongside theoretical description, the QSH materials library is surveyed with focus on the prospects for QSH-based device applications. In particular, theoretical predictions of nontrivial superconducting pairing in the QSH state toward Majorana-based topological quantum computing are discussed, which are the next frontier in QSH materials research.
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Affiliation(s)
- Michael S Lodge
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Shengyuan A Yang
- Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore, 487372, Singapore
| | - Shantanu Mukherjee
- Department of Physics, Indian Institute of Technology Madras, Chennai, Tamil Nadu, 600036, India
- Quantum Centres in Diamond and Emergent Materials (QCenDiem)-Group, IIT Madras, Chennai, Tamil Nadu, 600036, India
- Computational Materials Science Group, IIT Madras, Chennai, Tamil Nadu, 600036, India
| | - Bent Weber
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
- Australian Research Council (ARC) Centre of Excellence in Future Low-Energy Electronics Techonologies (FLEET), School of Physics, Monash University, Clayton, VIC, 3800, Australia
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27
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Perla P, Fonseka HA, Zellekens P, Deacon R, Han Y, Kölzer J, Mörstedt T, Bennemann B, Espiari A, Ishibashi K, Grützmacher D, Sanchez AM, Lepsa MI, Schäpers T. Fully in situ Nb/InAs-nanowire Josephson junctions by selective-area growth and shadow evaporation. NANOSCALE ADVANCES 2021; 3:1413-1421. [PMID: 36132855 PMCID: PMC9418346 DOI: 10.1039/d0na00999g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 01/17/2021] [Indexed: 06/14/2023]
Abstract
Josephson junctions based on InAs semiconducting nanowires and Nb superconducting electrodes are fabricated in situ by a special shadow evaporation scheme for the superconductor electrode. Compared to other metallic superconductors such as Al, Nb has the advantage of a larger superconducting gap which allows operation at higher temperatures and magnetic fields. Our junctions are fabricated by shadow evaporation of Nb on pairs of InAs nanowires grown selectively on two adjacent tilted Si (111) facets and crossing each other at a small distance. The upper wire relative to the deposition source acts as a shadow mask determining the gap of the superconducting electrodes on the lower nanowire. Electron microscopy measurements show that the fully in situ fabrication method gives a clean InAs/Nb interface. A clear Josephson supercurrent is observed in the current-voltage characteristics, which can be controlled by a bottom gate. The large excess current indicates a high junction transparency. Under microwave radiation, pronounced integer Shapiro steps are observed suggesting a sinusoidal current-phase relation. Owing to the large critical field of Nb, the Josephson supercurrent can be maintained to magnetic fields exceeding 1 T. Our results show that in situ prepared Nb/InAs nanowire contacts are very interesting candidates for superconducting quantum circuits requiring large magnetic fields.
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Affiliation(s)
- Pujitha Perla
- Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich 52425 Jülich Germany +49 2461 61 2940 +49 2461 61 2668
- JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance, Forschungszentrum Jülich, RWTH Aachen University Germany
| | - H Aruni Fonseka
- Department of Physics, University of Warwick Coventry CV4 7AL UK
| | - Patrick Zellekens
- Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich 52425 Jülich Germany +49 2461 61 2940 +49 2461 61 2668
- JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance, Forschungszentrum Jülich, RWTH Aachen University Germany
| | - Russell Deacon
- RIKEN Center for Emergent Matter Science and Advanced Device Laboratory 351-0198 Saitama Japan
| | - Yisong Han
- Department of Physics, University of Warwick Coventry CV4 7AL UK
| | - Jonas Kölzer
- Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich 52425 Jülich Germany +49 2461 61 2940 +49 2461 61 2668
- JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance, Forschungszentrum Jülich, RWTH Aachen University Germany
| | - Timm Mörstedt
- Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich 52425 Jülich Germany +49 2461 61 2940 +49 2461 61 2668
- JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance, Forschungszentrum Jülich, RWTH Aachen University Germany
| | - Benjamin Bennemann
- Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich 52425 Jülich Germany +49 2461 61 2940 +49 2461 61 2668
- JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance, Forschungszentrum Jülich, RWTH Aachen University Germany
| | - Abbas Espiari
- Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich 52425 Jülich Germany +49 2461 61 2940 +49 2461 61 2668
- JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance, Forschungszentrum Jülich, RWTH Aachen University Germany
| | - Koji Ishibashi
- RIKEN Center for Emergent Matter Science and Advanced Device Laboratory 351-0198 Saitama Japan
| | - Detlev Grützmacher
- Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich 52425 Jülich Germany +49 2461 61 2940 +49 2461 61 2668
- JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance, Forschungszentrum Jülich, RWTH Aachen University Germany
- Peter Grünberg Institut (PGI-10), Forschungszentrum Jülich 52425 Jülich Germany
| | - Ana M Sanchez
- Department of Physics, University of Warwick Coventry CV4 7AL UK
| | - Mihail Ion Lepsa
- JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance, Forschungszentrum Jülich, RWTH Aachen University Germany
- Peter Grünberg Institut (PGI-10), Forschungszentrum Jülich 52425 Jülich Germany
| | - Thomas Schäpers
- Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich 52425 Jülich Germany +49 2461 61 2940 +49 2461 61 2668
- JARA-Fundamentals of Future Information Technology, Jülich-Aachen Research Alliance, Forschungszentrum Jülich, RWTH Aachen University Germany
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28
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Udupa A, Banerjee A, Sengupta K, Sen D. One-dimensional spin-orbit coupled Dirac system with extended s-wave superconductivity: Majorana modes and Josephson effects. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:145301. [PMID: 33470985 DOI: 10.1088/1361-648x/abdd63] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 01/19/2021] [Indexed: 06/12/2023]
Abstract
Motivated by the spin-momentum locking of electrons at the boundaries of certain topological insulators, we study a one-dimensional system of spin-orbit coupled massless Dirac electrons withs-wave superconducting pairing. As a result of the spin-orbit coupling, our model has only two kinds of linearly dispersing modes, and we take these to be right-moving spin-up and left-moving spin-down. Both lattice and continuum models are studied. In the lattice model, we find that a single Majorana zero energy mode appears at each end of a finite system provided that thes-wave pairing has an extended form, with the nearest-neighbor pairing being larger than the on-site pairing. We confirm this both numerically and analytically by calculating the winding number. We find that the continuum model also has zero energy end modes. Next we study a lattice version of a model with both Schrödinger and Dirac-like terms and find that the model hosts a topological transition between topologically trivial and non-trivial phases depending on the relative strength of the Schrödinger and Dirac terms. We then study a continuum system consisting of twos-wave superconductors with different phases of the pairing, with aδ-function potential barrier lying at the junction of the two superconductors. Remarkably, we find that the system has asingleAndreev bound state (ABS) which is localized at the junction. When the pairing phase difference crosses a multiple of 2π, an ABS touches the top of the superconducting gap and disappears, and a different state appears from the bottom of the gap. We also study the AC Josephson effect in such a junction with a voltage bias that has both a constantV0and a term which oscillates with a frequencyω. We find that, in contrast to standard Josephson junctions, Shapiro plateaus appear when the Josephson frequencyωJ= 2eV0/ℏis a rational fraction ofω. We discuss experiments which can realize such junctions.
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Affiliation(s)
- Adithi Udupa
- Center for High Energy Physics, Indian Institute of Science, Bengaluru 560012, India
| | - Abhishek Banerjee
- Center for High Energy Physics, Indian Institute of Science, Bengaluru 560012, India
- Center for Quantum Devices and Microsoft Quantum Lab Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - K Sengupta
- School of Physical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
| | - Diptiman Sen
- Center for High Energy Physics, Indian Institute of Science, Bengaluru 560012, India
- Department of Physics, Indian Institute of Science, Bengaluru 560012, India
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29
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Kim MD. Circulator function in a Josephson junction circuit and braiding of Majorana zero modes. Sci Rep 2021; 11:1826. [PMID: 33469206 PMCID: PMC7815894 DOI: 10.1038/s41598-021-81503-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Accepted: 01/07/2021] [Indexed: 11/17/2022] Open
Abstract
We propose a scheme for the circulator function in a superconducting circuit consisting of a three-Josephson junction loop and a trijunction. In this study we obtain the exact Lagrangian of the system by deriving the effective potential from the fundamental boundary conditions. We subsequently show that we can selectively choose the direction of current flowing through the branches connected at the trijunction, which performs a circulator function. Further, we use this circulator function for a non-Abelian braiding of Majorana zero modes (MZMs). In the branches of the system we introduce pairs of MZMs which interact with each other through the phases of trijunction. The circulator function determines the phases of the trijunction and thus the coupling between the MZMs to gives rise to the braiding operation. We modify the system so that MZMs might be coupled to the external ones to perform qubit operations in a scalable design.
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Affiliation(s)
- Mun Dae Kim
- College of Liberal Arts, Hongik University, Sejong, 30016, Korea.
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30
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Li CZ, Wang AQ, Li C, Zheng WZ, Brinkman A, Yu DP, Liao ZM. Topological Transition of Superconductivity in Dirac Semimetal Nanowire Josephson Junctions. PHYSICAL REVIEW LETTERS 2021; 126:027001. [PMID: 33512215 DOI: 10.1103/physrevlett.126.027001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 12/18/2020] [Indexed: 06/12/2023]
Abstract
We report the topological transition by gate control in a Cd_{3}As_{2} Dirac semimetal nanowire Josephson junction with diameter of about 64 nm. In the electron branch, the quantum confinement effect enforces the surface band into a series of gapped subbands and thus nontopological states. In the hole branch, however, because the hole mean free path is smaller than the nanowire perimeter, the quantum confinement effect is inoperative and the topological property maintained. The superconductivity is enhanced by gate tuning from electron to hole conduction, manifested by a larger critical supercurrent and a larger critical magnetic field, which is attributed to the topological transition from gapped surface subbands to a gapless surface band. The gate-controlled topological transition of superconductivity should be valuable for manipulation of Majorana zero modes, providing a platform for future compatible and scalable design of topological qubits.
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Affiliation(s)
- Cai-Zhen Li
- Shenzhen Institute for Quantum Science and Engineering, and Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - An-Qi Wang
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Chuan Li
- MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
| | - Wen-Zhuang Zheng
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Alexander Brinkman
- MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
| | - Da-Peng Yu
- Shenzhen Institute for Quantum Science and Engineering, and Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Zhi-Min Liao
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Beijing Key Laboratory of Quantum Devices, Peking University, Beijing 100871, China
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31
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Lian CS, Si C, Duan W. Anisotropic Full-Gap Superconductivity in 2M-WS 2 Topological Metal with Intrinsic Proximity Effect. NANO LETTERS 2021; 21:709-715. [PMID: 33378208 DOI: 10.1021/acs.nanolett.0c04357] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Layered 2M-WS2 is recently observed to show Majorana bound states in vortices, but its superconducting pairing mechanism remains unknown, hindering the understanding of its topological superconducting nature. Using the ab initio Migdal-Eliashberg theory and electron-phonon Wannier interpolation, we demonstrate that both bulk and bilayer 2M-WS2 have a single anisotropic full-gap superconducting order of s-wave symmetry. We successfully reproduce the experimental superconducting critical temperature for the bulk and predict the bilayer 2M-WS2, a two-dimensional (2D) Z2 topological metal with nontrivial edge states right at the Fermi energy, to superconduct at 7 K, much higher than that in most 2D transition metal dichalcogenides (TMDs). A distinct proximity-enhanced surface superconductivity is further revealed by simulating quasiparticle density of states. This work unveils a universal electron-phonon full-gap pairing in 2M group VI TMDs and suggests a strong intrinsic surface-bulk proximity effect for 2M-WS2, paving the way to engineering topological superconductivity in TMD-based nanoscale devices.
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Affiliation(s)
- Chao-Sheng Lian
- International Laboratory for Quantum Functional Materials of Henan, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450001, China
| | - Chen Si
- School of Materials Science and Engineering, Beihang University, Beijing 100191, China
| | - Wenhui Duan
- Department of Physics and State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
- Institute for Advanced Study, Tsinghua University, Beijing 100084, China
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32
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Dartiailh MC, Cuozzo JJ, Elfeky BH, Mayer W, Yuan J, Wickramasinghe KS, Rossi E, Shabani J. Missing Shapiro steps in topologically trivial Josephson junction on InAs quantum well. Nat Commun 2021; 12:78. [PMID: 33397966 PMCID: PMC7782802 DOI: 10.1038/s41467-020-20382-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 11/27/2020] [Indexed: 01/29/2023] Open
Abstract
Josephson junctions hosting Majorana fermions have been predicted to exhibit a 4π periodic current phase relation. One experimental consequence of this periodicity is the disappearance of odd steps in Shapiro steps experiments. Experimentally, missing odd Shapiro steps have been observed in a number of materials systems with strong spin-orbit coupling and have been interpreted in the context of topological superconductivity. Here we report on missing odd steps in topologically trivial Josephson junctions fabricated on InAs quantum wells. We ascribe our observations to the high transparency of our junctions allowing Landau-Zener transitions. The probability of these processes is shown to be independent of the drive frequency. We analyze our results using a bi-modal transparency distribution which demonstrates that only few modes carrying 4π periodic current are sufficient to describe the disappearance of odd steps. Our findings highlight the elaborate circumstances that have to be considered in the investigation of the 4π Josephson junctions in relationship to topological superconductivity.
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Affiliation(s)
- Matthieu C Dartiailh
- Department of Physics, Center for Quantum Phenomena, New York University, New York, NY, 10003, USA
| | - Joseph J Cuozzo
- Department of Physics, William & Mary, Williamsburg, VA, 23187, USA
| | - Bassel H Elfeky
- Department of Physics, Center for Quantum Phenomena, New York University, New York, NY, 10003, USA
| | - William Mayer
- Department of Physics, Center for Quantum Phenomena, New York University, New York, NY, 10003, USA
| | - Joseph Yuan
- Department of Physics, Center for Quantum Phenomena, New York University, New York, NY, 10003, USA
| | | | - Enrico Rossi
- Department of Physics, William & Mary, Williamsburg, VA, 23187, USA
| | - Javad Shabani
- Department of Physics, Center for Quantum Phenomena, New York University, New York, NY, 10003, USA.
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33
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Chiu KL, Qian D, Qiu J, Liu W, Tan D, Mosallanejad V, Liu S, Zhang Z, Zhao Y, Yu D. Flux Tunable Superconducting Quantum Circuit Based on Weyl Semimetal MoTe 2. NANO LETTERS 2020; 20:8469-8475. [PMID: 33174417 DOI: 10.1021/acs.nanolett.0c02267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Weyl semimetals have drawn considerable attention for their exotic topological properties in many research fields. When in combination with s-wave superconductors, the supercurrent can be carried by their topological surface channels, forming junctions mimicking the behavior of Majorana bound states. Here, we present a transmon-like superconducting quantum intereference device (SQUID) consisting of lateral junctions made of Weyl semimetal Td-MoTe2 and superconducting leads of niobium nitride (NbN). The SQUID is coupled to a readout cavity made of molybdenum rhenium (MoRe), whose response at high power reveals the existence of the constituting Josephson junctions (JJs). The loop geometry of the circuit allows the resonant frequency of the readout cavity to be tuned by the magnetic flux. We demonstrate a JJ made of MoTe2 and a flux-tunable transmon-like circuit based on Weyl semimetals. Our study provides a platform to utilize topological materials in SQUID-based quantum circuits for potential applications in quantum information processing.
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Affiliation(s)
- Kuei-Lin Chiu
- Department of Physics, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
| | - Degui Qian
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Jiawei Qiu
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Weiyang Liu
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Dian Tan
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Vahid Mosallanejad
- Key Lab of Quantum Information, University of Science and Technology of China, Hefei 230026, China
| | - Song Liu
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Zongteng Zhang
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yue Zhao
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Dapeng Yu
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
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34
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Knapp C, Chew A, Alicea J. Fragility of the Fractional Josephson Effect in Time-Reversal-Invariant Topological Superconductors. PHYSICAL REVIEW LETTERS 2020; 125:207002. [PMID: 33258665 DOI: 10.1103/physrevlett.125.207002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 10/01/2020] [Indexed: 06/12/2023]
Abstract
Time-reversal-invariant topological superconductor (TRITOPS) wires host Majorana Kramers pairs that have been predicted to mediate a fractional Josephson effect with 4π periodicity in the superconducting phase difference. We explore the TRITOPS fractional Josephson effect in the presence of time-dependent "local mixing" perturbations that instantaneously preserve time-reversal symmetry. Specifically, we show that just as such couplings render braiding of Majorana Kramers pairs nonuniversal, the Josephson current becomes either aperiodic or 2π periodic (depending on conditions that we quantify) unless the phase difference is swept sufficiently quickly. We further analyze topological superconductors with T^{2}=+1 time-reversal symmetry and reveal a rich interplay between interactions and local mixing that can be experimentally probed in nanowire arrays.
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Affiliation(s)
- Christina Knapp
- Department of Physics and Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
- Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, California 91125, USA
| | - Aaron Chew
- Department of Physics and Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
| | - Jason Alicea
- Department of Physics and Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
- Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, California 91125, USA
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35
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Larson TFQ, Zhao L, Arnault EG, Wei MT, Seredinski A, Li H, Watanabe K, Taniguchi T, Amet F, Finkelstein G. Zero Crossing Steps and Anomalous Shapiro Maps in Graphene Josephson Junctions. NANO LETTERS 2020; 20:6998-7003. [PMID: 32902995 DOI: 10.1021/acs.nanolett.0c01598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The AC Josephson effect manifests itself in the form of "Shapiro steps" of quantized voltage in Josephson junctions subject to radiofrequency (RF) radiation. This effect presents an early example of a driven-dissipative quantum phenomenon and is presently utilized in primary voltage standards. Shapiro steps have also become one of the standard tools to probe junctions made in a variety of novel materials. Here we study Shapiro steps in a widely tunable graphene-based Josephson junction in which the high-frequency dynamics is determined by the on-chip environment. We investigate the variety of patterns that can be obtained in this well-understood system depending on the carrier density, temperature, RF frequency, and magnetic field. Although the patterns of Shapiro steps can change drastically when just one parameter is varied, the overall trends can be understood and the behaviors straightforwardly simulated, showing some key differences from the conventional RCSJ model. The resulting understanding may help interpret similar measurements in more complex materials.
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Affiliation(s)
- Trevyn F Q Larson
- Department of Physics, Duke University, Durham, North Carolina 27708, United States
| | - Lingfei Zhao
- Department of Physics, Duke University, Durham, North Carolina 27708, United States
| | - Ethan G Arnault
- Department of Physics, Duke University, Durham, North Carolina 27708, United States
| | - Ming-Tso Wei
- Department of Physics, Duke University, Durham, North Carolina 27708, United States
| | - Andrew Seredinski
- Department of Physics, Duke University, Durham, North Carolina 27708, United States
| | - Henming Li
- Department of Physics and Astronomy, Appalachian State University, Boone, North Carolina 28607, United States
| | - Kenji Watanabe
- Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - François Amet
- Department of Physics and Astronomy, Appalachian State University, Boone, North Carolina 28607, United States
| | - Gleb Finkelstein
- Department of Physics, Duke University, Durham, North Carolina 27708, United States
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36
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Haidekker Galambos T, Hoffman S, Recher P, Klinovaja J, Loss D. Superconducting Quantum Interference in Edge State Josephson Junctions. PHYSICAL REVIEW LETTERS 2020; 125:157701. [PMID: 33095622 DOI: 10.1103/physrevlett.125.157701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 06/20/2020] [Accepted: 08/19/2020] [Indexed: 06/11/2023]
Abstract
We study superconducting quantum interference in a Josephson junction linked via edge states in two-dimensional (2D) insulators. We consider two scenarios in which the 2D insulator is either a topological or a trivial insulator supporting one-dimensional (1D) helical or nonhelical edge states, respectively. In equilibrium, we find that the qualitative dependence of critical supercurrent on the flux through the junction is insensitive to the helical nature of the mediating states and can, therefore, not be used to verify the topological features of the underlying insulator. However, upon applying a finite voltage bias smaller than the superconducting gap to a relatively long junction, the finite-frequency interference pattern in the nonequilibrium transport current is qualitatively different for helical edge states as compared to nonhelical ones.
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Affiliation(s)
| | - Silas Hoffman
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Department of Physics, University of Florida, Gainesville, Florida 32611, USA
| | - Patrik Recher
- Institut für Mathematische Physik, Technische Universität Braunschweig, D-38106 Braunschweig, Germany
- Laboratory for Emerging Nanometrology Braunschweig, D-38106 Braunschweig, Germany
| | - Jelena Klinovaja
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Daniel Loss
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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37
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Perconte D, Seurre K, Humbert V, Ulysse C, Sander A, Trastoy J, Zatko V, Godel F, Kidambi PR, Hofmann S, Zhang XP, Bercioux D, Bergeret FS, Dlubak B, Seneor P, Villegas JE. Long-Range Propagation and Interference of d-Wave Superconducting Pairs in Graphene. PHYSICAL REVIEW LETTERS 2020; 125:087002. [PMID: 32909764 DOI: 10.1103/physrevlett.125.087002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 06/22/2020] [Accepted: 07/22/2020] [Indexed: 06/11/2023]
Abstract
Recent experiments have shown that proximity with high-temperature superconductors induces unconventional superconducting correlations in graphene. Here, we demonstrate that those correlations propagate hundreds of nanometers, allowing for the unique observation of d-wave Andreev-pair interferences in YBa_{2}Cu_{3}O_{7}-graphene devices that behave as a Fabry-Perot cavity. The interferences show as a series of pronounced conductance oscillations analogous to those originally predicted by de Gennes-Saint-James for conventional metal-superconductor junctions. The present demonstration is pivotal to the study of exotic directional effects expected for nodal superconductivity in Dirac materials.
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Affiliation(s)
- D Perconte
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
- Laboratorio de Bajas Temperaturas y Altos Campos Magnéticos, Departamento de Física de la Materia Condensada, Instituto Nicolás Cabrera and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - K Seurre
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - V Humbert
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - C Ulysse
- Centre for Nanoscience and Nanotechnology, CNRS, Université Paris-Sud/Université Paris-Saclay, Boulevard Thomas Gobert, 91120 Palaiseau, France
| | - A Sander
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - J Trastoy
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - V Zatko
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - F Godel
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - P R Kidambi
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, 2400 Highland Avenue, Nashville, Tennessee 37212, USA
- Department of Engineering, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - S Hofmann
- Department of Engineering, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - X P Zhang
- Centro de Fisica de Materiales (CFM-MPC), Centro Mixto CSIC-UPV/EHU, 20018 Donostia-San Sebastián, Basque Country, Spain
- Donostia International Physics Center (DIPC), Manuel de Lardizabal, 4, 20018 Donostia-San Sebastián, Spain
| | - D Bercioux
- Donostia International Physics Center (DIPC), Manuel de Lardizabal, 4, 20018 Donostia-San Sebastián, Spain
- IKERBASQUE, Basque Foundation of Science, 48011 Bilbao, Basque Country, Spain
| | - F S Bergeret
- Centro de Fisica de Materiales (CFM-MPC), Centro Mixto CSIC-UPV/EHU, 20018 Donostia-San Sebastián, Basque Country, Spain
- Donostia International Physics Center (DIPC), Manuel de Lardizabal, 4, 20018 Donostia-San Sebastián, Spain
| | - B Dlubak
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - P Seneor
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - Javier E Villegas
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
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38
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Kononov A, Abulizi G, Qu K, Yan J, Mandrus D, Watanabe K, Taniguchi T, Schönenberger C. One-Dimensional Edge Transport in Few-Layer WTe 2. NANO LETTERS 2020; 20:4228-4233. [PMID: 32396010 PMCID: PMC7291355 DOI: 10.1021/acs.nanolett.0c00658] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
WTe2 is a layered transitional-metal dichalcogenide (TMD) with a number of intriguing topological properties. Recently, WTe2 has been predicted to be a higher-order topological insulator (HOTI) with topologically protected hinge states along the edges. The gapless nature of WTe2 complicates the observation of one-dimensional (1D) topological states in transport due to their small contribution relative to the bulk. Here, we study the behavior of the Josephson effect in magnetic field to distinguish edge from bulk transport. The Josephson effect in few-layer WTe2 reveals 1D states residing on the edges and steps. Moreover, our data demonstrates a combination of Josephson transport properties observed solely in another HOTI-bismuth, including Josephson transport over micrometer distances, extreme robustness in a magnetic field, and nonsinusoidal current-phase relation (CPR). Our observations strongly suggest the topological origin of the 1D states and that few-layer WTe2 is a HOTI.
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Affiliation(s)
- Artem Kononov
- Department
of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Institute
of Solid State Physics of the Russian Academy of Sciences - Chernogolovka, Moscow District, Academician Ossipyan
str. 2, Chernogolovka 142432, Russia
| | - Gulibusitan Abulizi
- Department
of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Kejian Qu
- Department
of Materials Science and Engineering, University
of Tennessee, Knoxville, Tennessee 37996, United States
| | - Jiaqiang Yan
- Department
of Materials Science and Engineering, University
of Tennessee, Knoxville, Tennessee 37996, United States
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - David Mandrus
- Department
of Materials Science and Engineering, University
of Tennessee, Knoxville, Tennessee 37996, United States
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Kenji Watanabe
- National
Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National
Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Christian Schönenberger
- Department
of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Swiss Nanoscience
Institute, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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39
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Blasi G, Taddei F, Arrachea L, Carrega M, Braggio A. Nonlocal Thermoelectricity in a Superconductor-Topological-Insulator-Superconductor Junction in Contact with a Normal-Metal Probe: Evidence for Helical Edge States. PHYSICAL REVIEW LETTERS 2020; 124:227701. [PMID: 32567914 DOI: 10.1103/physrevlett.124.227701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 02/05/2020] [Accepted: 05/15/2020] [Indexed: 06/11/2023]
Abstract
We consider a Josephson junction hosting a Kramers pair of helical edge states of a quantum spin Hall bar in contact with a normal-metal probe. In this hybrid system, the orbital phase, induced by a small magnetic field threading the junction known as a Doppler shift, combines with the conventional Josephson phase difference and originates an effect akin to a Zeeman field in the spectrum. As a consequence, when a temperature bias is applied to the superconducting terminals, a thermoelectric current is established in the normal probe. We argue that this purely nonlocal thermoelectric effect is a unique signature of the helical nature of the edge states coupled to superconducting leads and it can constitute a useful tool for probing the helical nature of the edge states in systems where the Hall bar configuration is difficult to achieve. We fully characterize thermoelectric response and performance of this hybrid junction in a wide range of parameters, demonstrating that the external magnetic flux inducing the Doppler shift can be used as a knob to control the thermoelectric response and the heat flow in a novel device based on topological junctions.
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Affiliation(s)
- Gianmichele Blasi
- NEST, Scuola Normale Superiore and Instituto Nanoscienze-CNR, I-56126 Pisa, Italy
| | - Fabio Taddei
- NEST, Scuola Normale Superiore and Instituto Nanoscienze-CNR, I-56126 Pisa, Italy
| | - Liliana Arrachea
- International Center for Advanced Studies, ECyT-UNSAM, Campus Miguelete, 25 de Mayo y Francia, 1650 Buenos Aires, Argentina
| | - Matteo Carrega
- NEST, Scuola Normale Superiore and Instituto Nanoscienze-CNR, I-56126 Pisa, Italy
| | - Alessandro Braggio
- NEST, Scuola Normale Superiore and Instituto Nanoscienze-CNR, I-56126 Pisa, Italy
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40
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Liu CW, Wang Z, Qiu RLJ, Gao XPA. Development of topological insulator and topological crystalline insulator nanostructures. NANOTECHNOLOGY 2020; 31:192001. [PMID: 31962300 DOI: 10.1088/1361-6528/ab6dfc] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Topological insulators (TIs), a class of quantum materials with time reversal symmetry protected gapless Dirac-surface states, have attracted intensive research interests due to their exotic electronic properties. Topological crystalline insulators (TCIs), whose gapless surface states are protected by the crystal symmetry, have recently been proposed and experimentally verified as a new class of TIs. With high surface-to-volume ratio, nanoscale TI and TCI materials such as nanowires and nanoribbons can have significantly enhanced contribution from surface states in carrier transport and are thus ideally suited for the fundamental studies of topologically protected surface state transport and nanodevice fabrication. This article will review the synthesis and transport device measurements of TIs and TCIs nanostructures.
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Affiliation(s)
- Chieh-Wen Liu
- Department of Physics, Case Western Reserve University, 2076 Adelbert Road, Cleveland, OH 44106, United States of America
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41
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Induced Topological Superconductivity in a BiSbTeSe 2-Based Josephson Junction. NANOMATERIALS 2020; 10:nano10040794. [PMID: 32326139 PMCID: PMC7221935 DOI: 10.3390/nano10040794] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 04/13/2020] [Accepted: 04/14/2020] [Indexed: 11/17/2022]
Abstract
A 4 π -periodic supercurrent through a Josephson junction can be a consequence of the presence of Majorana bound states. A systematic study of the radio frequency response for several temperatures and frequencies yields a concrete protocol for examining the 4 π -periodic contribution to the supercurrent. This work also reports the observation of a 4 π -periodic contribution to the supercurrent in BiSbTeSe 2 -based Josephson junctions. As a response to irradiation by radio frequency waves, the junctions showed an absence of the first Shapiro step. At high irradiation power, a qualitative correspondence to a model including a 4 π -periodic component to the supercurrent is found.
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42
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Ying J, He J, Yang G, Liu M, Lyu Z, Zhang X, Liu H, Zhao K, Jiang R, Ji Z, Fan J, Yang C, Jing X, Liu G, Cao X, Wang X, Lu L, Qu F. Magnitude and Spatial Distribution Control of the Supercurrent in Bi 2O 2Se-Based Josephson Junction. NANO LETTERS 2020; 20:2569-2575. [PMID: 32203670 DOI: 10.1021/acs.nanolett.0c00025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Many proposals for exploring topological quantum computation are based on superconducting quantum devices constructed on materials with strong spin-orbit coupling (SOC). For these devices, full control of both the magnitude and the spatial distribution of the supercurrent is highly demanded, but has been elusive up to now. We constructed a proximity-type Josephson junction on nanoplates of Bi2O2Se, a new emerging semiconductor with strong SOC. Through electrical gating, we show that the supercurrent can be fully turned ON and OFF, and its real-space pathways can be configured either through the bulk or along the edges. Our work demonstrates Bi2O2Se as a promising platform for constructing multifunctional hybrid superconducting devices as well as for searching for topological superconductivity.
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Affiliation(s)
- Jianghua Ying
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jiangbo He
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Guang Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Mingli Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhaozheng Lyu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiang Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Huaiyuan Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physics, Nankai University, Tianjin 300071, China
| | - Kui Zhao
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ruiyang Jiang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhongqing Ji
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Jie Fan
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Changli Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiunian Jing
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Guangtong Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Xuewei Cao
- School of Physics, Nankai University, Tianjin 300071, 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
| | - Li Lu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Fanming Qu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
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43
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Stehno MP, Ngabonziza P, Myoren H, Brinkman A. Josephson Effect and Charge Distribution in Thin Bi 2 Te 3 Topological Insulators. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1908351. [PMID: 32091158 DOI: 10.1002/adma.201908351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 01/24/2020] [Indexed: 06/10/2023]
Abstract
Thin layers of topological insulator materials are quasi-2D systems featuring a complex interplay between quantum confinement and topological band structure. To understand the role of the spatial distribution of carriers in electrical transport, the Josephson effect, magnetotransport, and weak anti-localization are studied in bottom-gated thin Bi2 Te3 topological insulator films. The experimental carrier densities are compared to a model based on the solutions of the self-consistent Schrödinger-Poisson equations and they are in excellent agreement. The modeling allows for a quantitative interpretation of the weak antilocalization correction to the conduction and of the critical current of Josephson junctions with weak links made from such films without any ad hoc assumptions.
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Affiliation(s)
- Martin P Stehno
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE, Enschede, The Netherlands
- Physikalisches Institut EP3, University of Würzburg, Am Hubland, 97070, Würzburg, Germany
| | - Prosper Ngabonziza
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE, Enschede, The Netherlands
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
- Department of Physics, University of Johannesburg, P.O. Box 524 Auckland Park, 2006, Johannesburg, South Africa
| | - Hiroaki Myoren
- Graduate school of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570, Japan
| | - Alexander Brinkman
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE, Enschede, The Netherlands
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44
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Manousakis J, Wille C, Altland A, Egger R, Flensberg K, Hassler F. Weak Measurement Protocols for Majorana Bound State Identification. PHYSICAL REVIEW LETTERS 2020; 124:096801. [PMID: 32202888 DOI: 10.1103/physrevlett.124.096801] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Accepted: 01/22/2020] [Indexed: 06/10/2023]
Abstract
We propose a continuous weak measurement protocol testing the nonlocality of Majorana bound states through current shot noise correlations. The experimental setup contains a topological superconductor island with three normal-conducting leads weakly coupled to different Majorana states. Putting one lead at finite voltage and measuring the shot noise correlations between the other two (grounded) leads, devices with true Majorana states are distinguished from those without by strong current correlations. The presence of true Majorana states manifests itself in unusually high noise levels or the near absence of noise, depending on the chosen device configuration. Monitoring the noise statistics amounts to a weak continuous measurement of the Majorana qubit and yields information similar to that of a full braiding protocol, but at much lower experimental effort. Our theory can be adapted to different platforms and should allow for the clear identification of Majorana states.
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Affiliation(s)
- J Manousakis
- Institut für theoretische Physik, Universität zu Köln, Zülpicher Straße 77, D-50937 Köln, Germany
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - C Wille
- Dahlem Center for Complex Quantum Systems, Physics Department, Freie Universität Berlin, D-14195 Berlin, Germany
| | - A Altland
- Institut für theoretische Physik, Universität zu Köln, Zülpicher Straße 77, D-50937 Köln, Germany
| | - R Egger
- Institut für Theoretische Physik, Heinrich Heine Universität, D-40225 Düsseldorf, Germany
| | - K Flensberg
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - F Hassler
- JARA-Institute for Quantum Information, RWTH Aachen University, D-52056 Aachen, Germany
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45
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Dartiailh MC, Hartinger S, Gourmelon A, Bendias K, Bartolomei H, Kamata H, Berroir JM, Fève G, Plaçais B, Lunczer L, Schlereth R, Buhmann H, Molenkamp LW, Bocquillon E. Dynamical Separation of Bulk and Edge Transport in HgTe-Based 2D Topological Insulators. PHYSICAL REVIEW LETTERS 2020; 124:076802. [PMID: 32142329 DOI: 10.1103/physrevlett.124.076802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 01/13/2020] [Indexed: 06/10/2023]
Abstract
Topological effects in edge states are clearly visible on short lengths only, thus largely impeding their studies. On larger distances, one may be able to dynamically enhance topological signatures by exploiting the high mobility of edge states with respect to bulk carriers. Our work on microwave spectroscopy highlights the response of the edges which host very mobile carriers, while bulk carriers are drastically slowed down in the gap. Though the edges are denser than expected, we establish that charge relaxation occurs on short timescales and suggest that edge states can be addressed selectively on timescales over which bulk carriers are frozen.
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Affiliation(s)
- Matthieu C Dartiailh
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | - Simon Hartinger
- Physikalisches Institut (EP3), Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
| | - Alexandre Gourmelon
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | - Kalle Bendias
- Physikalisches Institut (EP3), Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
| | - Hugo Bartolomei
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | - Hiroshi Kamata
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | - Jean-Marc Berroir
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | - Gwendal Fève
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | - Bernard Plaçais
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | - Lukas Lunczer
- Physikalisches Institut (EP3), Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
| | - Raimund Schlereth
- Physikalisches Institut (EP3), Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
| | - Hartmut Buhmann
- Physikalisches Institut (EP3), Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
| | - Laurens W Molenkamp
- Physikalisches Institut (EP3), Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
| | - Erwann Bocquillon
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
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46
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Pan XH, Yang KJ, Chen L, Xu G, Liu CX, Liu X. Lattice-Symmetry-Assisted Second-Order Topological Superconductors and Majorana Patterns. PHYSICAL REVIEW LETTERS 2019; 123:156801. [PMID: 31702286 DOI: 10.1103/physrevlett.123.156801] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Indexed: 06/10/2023]
Abstract
We propose a realization of the lattice-symmetry-assisted second-order topological superconductors with corner Majorana zero modes (MZM) based on two-dimensional topological insulators (2DTI). The lattice symmetry can naturally lead to the anisotropic coupling of edge states along different directions to the in-plane magnetic field and conventional s-wave pairings, thus leading to a single MZM located at the corners for various lattice patterns. In particular, we focus on the 2DTI with D_{3d} lattice symmetry and found different types of gap opening for the edge states along the armchair and zigzag edges in a broad range of parameters. As a consequence, a single MZM exists at the corner between the zigzag and armchair edges, and is robust against weakly broken lattice symmetry. We propose to realize such corner MZMs in a variety of polygon patterns, such as triangles and quadrilaterals. We further show their potentials in building the Majorana network through constructing the Majorana Y junction under an in-plane magnetic field.
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Affiliation(s)
- Xiao-Hong Pan
- School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
- Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Kai-Jie Yang
- School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
- Department of Physics, the Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Li Chen
- School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
- Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Gang Xu
- School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
- Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Chao-Xing Liu
- Department of Physics, the Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Xin Liu
- School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
- Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
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47
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Bocquillon E. A Majorana mass production line. NATURE NANOTECHNOLOGY 2019; 14:815-817. [PMID: 31358943 DOI: 10.1038/s41565-019-0495-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Affiliation(s)
- Erwann Bocquillon
- Laboratoire de Physique de l'Ecole Normale Supérieure, Paris, France.
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48
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Schüffelgen P, Rosenbach D, Li C, Schmitt TW, Schleenvoigt M, Jalil AR, Schmitt S, Kölzer J, Wang M, Bennemann B, Parlak U, Kibkalo L, Trellenkamp S, Grap T, Meertens D, Luysberg M, Mussler G, Berenschot E, Tas N, Golubov AA, Brinkman A, Schäpers T, Grützmacher D. Selective area growth and stencil lithography for in situ fabricated quantum devices. NATURE NANOTECHNOLOGY 2019; 14:825-831. [PMID: 31358942 DOI: 10.1038/s41565-019-0506-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 06/14/2019] [Indexed: 06/10/2023]
Abstract
The interplay of Dirac physics and induced superconductivity at the interface of a 3D topological insulator (TI) with an s-wave superconductor (S) provides a new platform for topologically protected quantum computation based on elusive Majorana modes. To employ such S-TI hybrid devices in future topological quantum computation architectures, a process is required that allows for device fabrication under ultrahigh vacuum conditions. Here, we report on the selective area growth of (Bi,Sb)2Te3 TI thin films and stencil lithography of superconductive Nb for a full in situ fabrication of S-TI hybrid devices via molecular-beam epitaxy. A dielectric capping layer was deposited as a final step to protect the delicate surfaces of the S-TI hybrids at ambient conditions. Transport experiments in as-prepared Josephson junctions show highly transparent S-TI interfaces and a missing first Shapiro step, which indicates the presence of Majorana bound states. To move from single junctions towards complex circuitry for future topological quantum computation architectures, we monolithically integrated two aligned hardmasks to the substrate prior to growth. The presented process provides new possibilities to deliberately combine delicate quantum materials in situ at the nanoscale.
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Affiliation(s)
- Peter Schüffelgen
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany.
- Helmholtz Virtual Institute for Topological Insulators (VITI), Forschungszentrum Jülich, Jülich, Germany.
| | - Daniel Rosenbach
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany
- Helmholtz Virtual Institute for Topological Insulators (VITI), Forschungszentrum Jülich, Jülich, Germany
| | - Chuan Li
- MESA+ Institute, University of Twente, Enschede, The Netherlands
| | - Tobias W Schmitt
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany
- JARA-FIT Institute Green IT, RWTH Aachen University, Aachen, Germany
| | - Michael Schleenvoigt
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany
| | - Abdur R Jalil
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany
| | - Sarah Schmitt
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany
| | - Jonas Kölzer
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany
| | - Meng Wang
- Helmholtz Virtual Institute for Topological Insulators (VITI), Forschungszentrum Jülich, Jülich, Germany
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, China
| | - Benjamin Bennemann
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany
| | - Umut Parlak
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany
| | - Lidia Kibkalo
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany
| | | | - Thomas Grap
- Institute of Semiconductor Electronics, RWTH Aachen University, Aachen, Germany
| | - Doris Meertens
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany
| | - Martina Luysberg
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany
| | - Gregor Mussler
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany
- Helmholtz Virtual Institute for Topological Insulators (VITI), Forschungszentrum Jülich, Jülich, Germany
| | - Erwin Berenschot
- MESA+ Institute, University of Twente, Enschede, The Netherlands
| | - Niels Tas
- MESA+ Institute, University of Twente, Enschede, The Netherlands
| | | | | | - Thomas Schäpers
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany
- Helmholtz Virtual Institute for Topological Insulators (VITI), Forschungszentrum Jülich, Jülich, Germany
| | - Detlev Grützmacher
- Peter Grünberg Institute, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, Jülich, Germany
- Helmholtz Virtual Institute for Topological Insulators (VITI), Forschungszentrum Jülich, Jülich, Germany
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49
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Lunczer L, Leubner P, Endres M, Müller VL, Brüne C, Buhmann H, Molenkamp LW. Approaching Quantization in Macroscopic Quantum Spin Hall Devices through Gate Training. PHYSICAL REVIEW LETTERS 2019; 123:047701. [PMID: 31491275 DOI: 10.1103/physrevlett.123.047701] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2019] [Revised: 04/24/2019] [Indexed: 06/10/2023]
Abstract
Quantum spin Hall edge channels hold great promise as dissipationless one-dimensional conductors. However, the ideal quantized conductance of 2e^{2}/h is only found in very short channels-in contradiction with the expected protection against backscattering of the topological insulator state. In this Letter we show that enhancing the band gap does not improve quantization. When we instead alter the potential landscape by charging trap states in the gate dielectric using gate training, we approach conductance quantization for macroscopically long channels. Effectively, the scattering length increases to 175 μm, more than 1 order of magnitude longer than in previous works for HgTe-based quantum wells. Our experiments show that the distortion of the potential landscape by impurities, leading to puddle formation in the narrow gap material, is the major obstacle for observing undisturbed quantum spin Hall edge channel transport.
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Affiliation(s)
- Lukas Lunczer
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, D-97074 Würzburg, Germany
| | - Philipp Leubner
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Martin Endres
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Valentin L Müller
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, D-97074 Würzburg, Germany
| | - Christoph Brüne
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Hartmut Buhmann
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, D-97074 Würzburg, Germany
| | - Laurens W Molenkamp
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, D-97074 Würzburg, Germany
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50
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Hajer J, Kessel M, Brüne C, Stehno MP, Buhmann H, Molenkamp LW. Proximity-Induced Superconductivity in CdTe-HgTe Core-Shell Nanowires. NANO LETTERS 2019; 19:4078-4082. [PMID: 31120766 DOI: 10.1021/acs.nanolett.9b01472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In this Letter we report on proximity superconductivity induced in CdTe-HgTe core-shell nanowires, a quasi-one-dimensional heterostructure of the topological insulator HgTe. We demonstrate a Josephson supercurrent in our nanowires contacted with superconducting Al leads. The observation of a sizable Ic Rn product, a positive excess current, and multiple Andreev reflections up to fourth order further indicate a high interface quality of the junctions.
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Affiliation(s)
- Jan Hajer
- Institute for Topological Insulators and Physikalisches Institut (EP3) , Universität Würzburg , Am Hubland , DE-97074 Würzburg , Germany
| | - Maximilian Kessel
- Institute for Topological Insulators and Physikalisches Institut (EP3) , Universität Würzburg , Am Hubland , DE-97074 Würzburg , Germany
| | - Christoph Brüne
- Institute for Topological Insulators and Physikalisches Institut (EP3) , Universität Würzburg , Am Hubland , DE-97074 Würzburg , Germany
| | - Martin P Stehno
- Institute for Topological Insulators and Physikalisches Institut (EP3) , Universität Würzburg , Am Hubland , DE-97074 Würzburg , Germany
| | - Hartmut Buhmann
- Institute for Topological Insulators and Physikalisches Institut (EP3) , Universität Würzburg , Am Hubland , DE-97074 Würzburg , Germany
| | - Laurens W Molenkamp
- Institute for Topological Insulators and Physikalisches Institut (EP3) , Universität Würzburg , Am Hubland , DE-97074 Würzburg , Germany
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