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Guo Z, Han M, Zeng S, Yin Z, Tan J, Niu K, Zhao E, Zhao Y, Liu B, Zou X, Lin J. Intrinsic Grain Boundary Structure and Enhanced Defect States in Air-Sensitive Polycrystalline 1T'-WTe 2 Monolayer. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2402219. [PMID: 38843883 DOI: 10.1002/adma.202402219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2024] [Revised: 05/03/2024] [Indexed: 06/15/2024]
Abstract
Monolayer WTe2 has attracted significant attention for its unconventional superconductivity and topological edge states. However, its air sensitivity poses challenges for studying intrinsic defect structures. This study addresses this issue using a custom-built inert gas interconnected system, and investigate the intrinsic grain boundary (GB) structures of monolayer polycrystalline 1T' WTe2 grown by nucleation-controlled chemical vapor deposition (CVD) method. These findings reveal that GBs in this system are predominantly governed by W-Te rhombi with saturated coordination, resulting in three specific GB prototypes without dislocation cores. The GBs exhibit anisotropic orientations influenced by kinks formed from these fundamental units, which in turn affect the distribution of grains in various shapes within polycrystalline flakes. Scanning tunneling microscopy/spectroscopy (STM/S) analysis further reveals metallic states along the intrinsic 120° twin grain boundary (TGB), consistent with computed band structures. This systematic exploration of GBs in air-sensitive 1T' WTe2 monolayers provides valuable insights into emerging GB-related phenomena.
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Affiliation(s)
- Zenglong Guo
- Department of Physics and Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
| | - Mengjiao Han
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Shengfeng Zeng
- Shenzhen Geim Graphene Center, Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, China
| | - Zhouyi Yin
- Department of Physics and Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
| | - Junyang Tan
- Shenzhen Geim Graphene Center, Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, China
| | - Kangdi Niu
- Department of Physics and Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
| | - Erding Zhao
- Department of Physics and Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
| | - Yue Zhao
- Department of Physics and Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
| | - Bilu Liu
- Shenzhen Geim Graphene Center, Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, China
| | - Xiaolong Zou
- Shenzhen Geim Graphene Center, Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, China
| | - Junhao Lin
- Department of Physics and Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
- Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area (Guangdong), Shenzhen, 518045, China
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2
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Yang YB, Wang JH, Li K, Xu Y. Higher-order topological phases in crystalline and non-crystalline systems: a review. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:283002. [PMID: 38574683 DOI: 10.1088/1361-648x/ad3abd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 04/04/2024] [Indexed: 04/06/2024]
Abstract
In recent years, higher-order topological phases have attracted great interest in various fields of physics. These phases have protected boundary states at lower-dimensional boundaries than the conventional first-order topological phases due to the higher-order bulk-boundary correspondence. In this review, we summarize current research progress on higher-order topological phases in both crystalline and non-crystalline systems. We firstly introduce prototypical models of higher-order topological phases in crystals and their topological characterizations. We then discuss effects of quenched disorder on higher-order topology and demonstrate disorder-induced higher-order topological insulators. We also review the theoretical studies on higher-order topological insulators in amorphous systems without any crystalline symmetry and higher-order topological phases in non-periodic lattices including quasicrystals, hyperbolic lattices, and fractals, which have no crystalline counterparts. We conclude the review by a summary of experimental realizations of higher-order topological phases and discussions on potential directions for future study.
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Affiliation(s)
- Yan-Bin Yang
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong Special Administrative Region of China, People's Republic of China
- Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, People's Republic of China
| | - Jiong-Hao Wang
- Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, People's Republic of China
| | - Kai Li
- Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, People's Republic of China
| | - Yong Xu
- Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, People's Republic of China
- Hefei National Laboratory, Hefei 230088, People's Republic of China
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3
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Le T, Zhang R, Li C, Jiang R, Sheng H, Tu L, Cao X, Lyu Z, Shen J, Liu G, Liu F, Wang Z, Lu L, Qu F. Magnetic field filtering of the boundary supercurrent in unconventional metal NiTe 2-based Josephson junctions. Nat Commun 2024; 15:2785. [PMID: 38555347 PMCID: PMC10981750 DOI: 10.1038/s41467-024-47103-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 03/15/2024] [Indexed: 04/02/2024] Open
Abstract
Topological materials with boundary (surface/edge/hinge) states have attracted tremendous research interest. Additionally, unconventional (obstructed atomic) materials have recently drawn lots of attention owing to their obstructed boundary states. Experimentally, Josephson junctions (JJs) constructed on materials with boundary states produce the peculiar boundary supercurrent, which was utilized as a powerful diagnostic approach. Here, we report the observations of boundary supercurrent in NiTe2-based JJs. Particularly, applying an in-plane magnetic field along the Josephson current can rapidly suppress the bulk supercurrent and retain the nearly pure boundary supercurrent, namely the magnetic field filtering of supercurrent. Further systematic comparative analysis and theoretical calculations demonstrate the existence of unconventional nature and obstructed hinge states in NiTe2, which could produce hinge supercurrent that accounts for the observation. Our results reveal the probable hinge states in unconventional metal NiTe2, and demonstrate in-plane magnetic field as an efficient method to filter out the bulk contributions and thereby to highlight the hinge states hidden in topological/unconventional materials.
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Affiliation(s)
- Tian Le
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Ruihan Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Changcun Li
- School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, China
| | - Ruiyang Jiang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Haohao Sheng
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Linfeng Tu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- School of Physics, Nankai University, Tianjin, China
| | - Xuewei Cao
- School of Physics, Nankai University, Tianjin, China
| | - Zhaozheng Lyu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- Hefei National Laboratory, Hefei, China
| | - Jie Shen
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, China
| | - Guangtong Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- Hefei National Laboratory, Hefei, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, China
| | - Fucai Liu
- School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, China.
- Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou, China.
| | - Zhijun Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China.
| | - Li Lu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China.
- Hefei National Laboratory, Hefei, China.
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, China.
| | - Fanming Qu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China.
- Hefei National Laboratory, Hefei, China.
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, China.
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4
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Kim JK, Jeon KR, Sivakumar PK, Jeon J, Koerner C, Woltersdorf G, Parkin SSP. Intrinsic supercurrent non-reciprocity coupled to the crystal structure of a van der Waals Josephson barrier. Nat Commun 2024; 15:1120. [PMID: 38321041 PMCID: PMC10847146 DOI: 10.1038/s41467-024-45298-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Accepted: 01/17/2024] [Indexed: 02/08/2024] Open
Abstract
Non-reciprocal electronic transport in a spatially homogeneous system arises from the simultaneous breaking of inversion and time-reversal symmetries. Superconducting and Josephson diodes, a key ingredient for future non-dissipative quantum devices, have recently been realized. Only a few examples of a vertical superconducting diode effect have been reported and its mechanism, especially whether intrinsic or extrinsic, remains elusive. Here we demonstrate a substantial supercurrent non-reciprocity in a van der Waals vertical Josephson junction formed with a Td-WTe2 barrier and NbSe2 electrodes that clearly reflects the intrinsic crystal structure of Td-WTe2. The Josephson diode efficiency increases with the Td-WTe2 thickness up to critical thickness, and all junctions, irrespective of the barrier thickness, reveal magneto-chiral characteristics with respect to a mirror plane of Td-WTe2. Our results, together with the twist-angle-tuned magneto-chirality of a Td-WTe2 double-barrier junction, show that two-dimensional materials promise vertical Josephson diodes with high efficiency and tunability.
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Affiliation(s)
- Jae-Keun Kim
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120, Halle (Saale), Germany.
| | - Kun-Rok Jeon
- Department of Physics, Chung-Ang University (CAU), Seoul, 06974, Republic of Korea
| | - Pranava K Sivakumar
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120, Halle (Saale), Germany
| | - Jaechun Jeon
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120, Halle (Saale), Germany
| | - Chris Koerner
- Department of Physics, Martin Luther University Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120, Halle, Germany
| | - Georg Woltersdorf
- Department of Physics, Martin Luther University Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120, Halle, Germany
| | - Stuart S P Parkin
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120, Halle (Saale), Germany.
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5
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Chen P, Wang J, Wang G, Ye B, Zhou L, Wang L, Wang J, Zhang W, Chen W, Mei J, He H. Asymmetric edge supercurrents in MoTe 2 Josephson junctions. NANOSCALE ADVANCES 2024; 6:690-696. [PMID: 38235086 PMCID: PMC10791112 DOI: 10.1039/d3na00884c] [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: 10/14/2023] [Accepted: 12/13/2023] [Indexed: 01/19/2024]
Abstract
To investigate the higher order topology in MoTe2, the supercurrent interference phenomena in Nb/MoTe2/Nb planar Josephson junctions have been systematically studied. By analyzing the obtained interference pattern of the critical supercurrents and performing a comparative study of the edge-touched and untouched junctions, it's found that the supercurrent is dominated by the edges, rather than the bulk or surfaces of MoTe2. An asymmetric Josephson effect with a field-tunable sign is also observed, indicating the nontrivial origin of the edge states. These results not only provide initial evidence for the hinge states in the higher order topological insulator MoTe2, but also demonstrate the potential applications of MoTe2-based Josephson junctions in rectifying the supercurrent.
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Affiliation(s)
- Pingbo Chen
- Department of Physics, Harbin Institute of Technology Harbin 150001 China
- Department of Physics, Southern University of Science and Technology Shenzhen 518055 China
| | - Jinhua Wang
- Department of Physics, Southern University of Science and Technology Shenzhen 518055 China
| | - Gongqi Wang
- Department of Physics, Southern University of Science and Technology Shenzhen 518055 China
| | - Bicong Ye
- Department of Physics, Southern University of Science and Technology Shenzhen 518055 China
- Department of Physics, The Hong Kong University of Science and Technology Clear Water Bay Hong Kong 999077 China
| | - Liang Zhou
- Department of Physics, Southern University of Science and Technology Shenzhen 518055 China
| | - Le Wang
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology Shenzhen 518055 China
| | - Jiannong Wang
- Department of Physics, The Hong Kong University of Science and Technology Clear Water Bay Hong Kong 999077 China
| | - Wenqing Zhang
- Department of Materials Science and Engineering, Southern University of Science and Technology Shenzhen 518055 China
- Shenzhen Key Laboratory for Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology Shenzhen 518055 China
| | - Weiqiang Chen
- Department of Physics, Southern University of Science and Technology Shenzhen 518055 China
- Shenzhen Key Laboratory for Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology Shenzhen 518055 China
| | - Jiawei Mei
- Department of Physics, Southern University of Science and Technology Shenzhen 518055 China
- Shenzhen Key Laboratory for Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology Shenzhen 518055 China
| | - Hongtao He
- Department of Physics, Southern University of Science and Technology Shenzhen 518055 China
- Shenzhen Key Laboratory for Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology Shenzhen 518055 China
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6
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Chu CG, Chen JJ, Wang AQ, Tan ZB, Li CZ, Li C, Brinkman A, Xiang PZ, Li N, Pan ZC, Lu HZ, Yu D, Liao ZM. Broad and colossal edge supercurrent in Dirac semimetal Cd 3As 2 Josephson junctions. Nat Commun 2023; 14:6162. [PMID: 37788988 PMCID: PMC10547728 DOI: 10.1038/s41467-023-41815-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 09/12/2023] [Indexed: 10/05/2023] Open
Abstract
Edge supercurrent has attracted great interest recently due to its crucial role in achieving and manipulating topological superconducting states. Proximity-induced superconductivity has been realized in quantum Hall and quantum spin Hall edge states, as well as in higher-order topological hinge states. Non-Hermitian skin effect, the aggregation of non-Bloch eigenstates at open boundaries, promises an abnormal edge channel. Here we report the observation of broad edge supercurrent in Dirac semimetal Cd3As2-based Josephson junctions. The as-grown Cd3As2 nanoplates are electron-doped by intrinsic defects, which enhance the non-Hermitian perturbations. The superconducting quantum interference indicates edge supercurrent with a width of ~1.6 μm and a magnitude of ~1 μA at 10 mK. The wide and large edge supercurrent is inaccessible for a conventional edge system and suggests the presence of non-Hermitian skin effect. A supercurrent nonlocality is also observed. The interplay between band topology and non-Hermiticity is beneficial for exploiting exotic topological matter.
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Affiliation(s)
- Chun-Guang Chu
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China
| | - Jing-Jing Chen
- Shenzhen Institute for Quantum Science and Engineering, Department of Physics, Southern University of Science and Technology, 518055, Shenzhen, China
- International Quantum Academy, 518048, Shenzhen, China
| | - An-Qi Wang
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China.
| | - Zhen-Bing Tan
- Shenzhen Institute for Quantum Science and Engineering, Department of Physics, Southern University of Science and Technology, 518055, Shenzhen, China.
- International Quantum Academy, 518048, Shenzhen, China.
| | - Cai-Zhen Li
- Shenzhen Institute for Quantum Science and Engineering, Department of Physics, Southern University of Science and Technology, 518055, Shenzhen, China
- International Quantum Academy, 518048, Shenzhen, China
| | - Chuan Li
- MESA+ Institute for Nanotechnology, University of Twente, 7500 AE, Enschede, The Netherlands
| | - Alexander Brinkman
- MESA+ Institute for Nanotechnology, University of Twente, 7500 AE, Enschede, The Netherlands
| | - Peng-Zhan Xiang
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China
| | - Na Li
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China
| | - Zhen-Cun Pan
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China
| | - Hai-Zhou Lu
- Shenzhen Institute for Quantum Science and Engineering, Department of Physics, Southern University of Science and Technology, 518055, Shenzhen, China
| | - Dapeng Yu
- Shenzhen Institute for Quantum Science and Engineering, Department of Physics, Southern University of Science and Technology, 518055, Shenzhen, China
- International Quantum Academy, 518048, Shenzhen, China
- Hefei National Laboratory, 230088, Hefei, China
| | - Zhi-Min Liao
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China.
- Hefei National Laboratory, 230088, Hefei, China.
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7
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Wang Y, Yang SY, Sivakumar PK, Ortiz BR, Teicher SML, Wu H, Srivastava AK, Garg C, Liu D, Parkin SSP, Toberer ES, McQueen T, Wilson SD, Ali MN. Anisotropic proximity-induced superconductivity and edge supercurrent in Kagome metal, K 1-xV 3Sb 5. SCIENCE ADVANCES 2023; 9:eadg7269. [PMID: 37436976 DOI: 10.1126/sciadv.adg7269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 06/12/2023] [Indexed: 07/14/2023]
Abstract
Materials with Kagome nets are of particular importance for their potential combination of strong correlation, exotic magnetism, and electronic topology. KV3Sb5 was discovered to be a layered topological metal with a Kagome net of vanadium. Here, we fabricated Josephson Junctions of K1-xV3Sb5 and induced superconductivity over long junction lengths. Through magnetoresistance and current versus phase measurements, we observed a magnetic field sweeping direction-dependent magnetoresistance and an anisotropic interference pattern with a Fraunhofer pattern for in-plane magnetic field but a suppression of critical current for out-of-plane magnetic field. These results indicate an anisotropic internal magnetic field in K1-xV3Sb5 that influences the superconducting coupling in the junction, possibly giving rise to spin-triplet superconductivity. In addition, the observation of long-lived fast oscillations shows evidence of spatially localized conducting channels arising from edge states. These observations pave the way for studying unconventional superconductivity and Josephson device based on Kagome metals with electron correlation and topology.
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Affiliation(s)
- Yaojia Wang
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Shuo-Ying Yang
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
| | - Pranava K Sivakumar
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
| | - Brenden R Ortiz
- Materials Department, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Samuel M L Teicher
- Materials Department, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Heng Wu
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Abhay K Srivastava
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
| | - Chirag Garg
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
- IBM Almaden Research Center, San Jose, CA 95120, USA
| | - Defa Liu
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
- Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Stuart S P Parkin
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
| | | | | | - Stephen D Wilson
- Materials Department, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Mazhar N Ali
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
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8
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Endres M, Kononov A, Arachchige HS, Yan J, Mandrus D, Watanabe K, Taniguchi T, Schönenberger C. Current-Phase Relation of a WTe 2 Josephson Junction. NANO LETTERS 2023; 23:4654-4659. [PMID: 37155691 DOI: 10.1021/acs.nanolett.3c01416] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
When a topological insulator is incorporated into a Josephson junction, the system is predicted to reveal the fractional Josephson effect with a 4π-periodic current-phase relation. Here, we report the measurement of a 4π-periodic switching current through an asymmetric SQUID, formed by the higher-order topological insulator WTe2. Contrary to the established opinion, we show that a high asymmetry in critical current and negligible loop inductance are not sufficient by themselves to reliably measure the current-phase relation. Instead, we find that our measurement is heavily influenced by additional inductances originating from the self-formed PdTex inside the junction. We therefore develop a method to numerically recover the current-phase relation of the system and find the 1.5 μm long junction to be best described in the short ballistic limit. Our results highlight the complexity of subtle inductance effects that can give rise to misleading topological signatures in transport measurements.
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Affiliation(s)
- Martin Endres
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - Artem Kononov
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - Hasitha Suriya Arachchige
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Jiaqiang Yan
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
- Material Science and Technology Division, Oak Ridge Laboratory, Oak Ridge, Tennessee 37831, United States
| | - David Mandrus
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
- Material Science and Technology Division, Oak Ridge Laboratory, Oak Ridge, Tennessee 37831, United States
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Christian Schönenberger
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
- Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
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9
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Lee J, Kwon J, Lee E, Park J, Cha S, Watanabe K, Taniguchi T, Jo MH, Choi H. Spinful hinge states in the higher-order topological insulators WTe 2. Nat Commun 2023; 14:1801. [PMID: 37002230 PMCID: PMC10066182 DOI: 10.1038/s41467-023-37482-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 03/20/2023] [Indexed: 04/03/2023] Open
Abstract
Higher-order topological insulators are recently discovered quantum materials exhibiting distinct topological phases with the generalized bulk-boundary correspondence. Td-WTe2 is a promising candidate to reveal topological hinge excitation in an atomically thin regime. However, with initial theories and experiments focusing on localized one-dimensional conductance only, no experimental reports exist on how the spin orientations are distributed over the helical hinges-this is critical, yet one missing puzzle. Here, we employ the magneto-optic Kerr effect to visualize the spinful characteristics of the hinge states in a few-layer Td-WTe2. By examining the spin polarization of electrons injected from WTe2 to graphene under external electric and magnetic fields, we conclude that WTe2 hosts a spinful and helical topological hinge state protected by the time-reversal symmetry. Our experiment provides a fertile diagnosis to investigate the topologically protected gapless hinge states, and may call for new theoretical studies to extend the previous spinless model.
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Affiliation(s)
- Jekwan Lee
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea
- Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Jaehyeon Kwon
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea
- Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Eunho Lee
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea
- Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Jiwon Park
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea
- Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Soonyoung Cha
- Center for Epitaxial van der Waals Quantum Solids, Institute for Basic Science, Pohang, 37673, Korea
- Department of Materials Science and Engineering, Pohang University of Science and Technoloagy, Pohang, 37673, Korea
| | - 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
| | - Moon-Ho Jo
- Center for Epitaxial van der Waals Quantum Solids, Institute for Basic Science, Pohang, 37673, Korea
- Department of Materials Science and Engineering, Pohang University of Science and Technoloagy, Pohang, 37673, Korea
| | - Hyunyong Choi
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea.
- Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea.
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10
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Souto RS, Leijnse M, Schrade C. Josephson Diode Effect in Supercurrent Interferometers. PHYSICAL REVIEW LETTERS 2022; 129:267702. [PMID: 36608204 DOI: 10.1103/physrevlett.129.267702] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Revised: 10/10/2022] [Accepted: 12/02/2022] [Indexed: 06/17/2023]
Abstract
A Josephson diode is a nonreciprocal circuit element that supports a larger dissipationless supercurrent in one direction than in the other. In this Letter, we propose a class of Josephson diodes based on supercurrent interferometers composed of Andreev bound state Josephson junctions or interacting quantum dot Josephson junctions, which are not diodes themselves but possess nonsinusoidal current-phase relations. We show that such Josephson diodes have several important advantages, like being electrically tunable and requiring only time-reversal breaking by a magnetic flux. We also show that our diodes have a characteristic ac response, revealed by the Shapiro steps. Even the simplest realization of our Josephson diode paradigm that relies on only two junctions can achieve efficiencies of up to ∼40% and, interestingly, far greater efficiencies are achievable by concatenating interferometer loops. We hope that our Letter will stimulate the search for highly tunable Josephson diode effects in Josephson devices based semiconductor-superconductor hybrids, 2d materials, and topological insulators, where nonsinusoidal current-phase relations were recently observed.
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Affiliation(s)
- Rubén Seoane Souto
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Division of Solid State Physics and NanoLund, Lund University, S-22100 Lund, Sweden
| | - Martin Leijnse
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Division of Solid State Physics and NanoLund, Lund University, S-22100 Lund, Sweden
| | - Constantin Schrade
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
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11
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Guo M, Gu S, Xu S, Lu J, Wang Y, Zhou G. Design, synthesis and application of two-dimensional metal tellurides as high-performance electrode materials. Front Chem 2022; 10:1023003. [PMID: 36226125 PMCID: PMC9548651 DOI: 10.3389/fchem.2022.1023003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 08/31/2022] [Indexed: 11/22/2022] Open
Abstract
Multifunctional electrode materials with inherent conductivity have attracted extensive attention in recent years. Two-dimensional (2D) metal telluride nanomaterials are more promising owing to their strong metallic properties and unique physical/chemical merits. In this review, recent advancements in the preparation of 2D metal tellurides and their application in electrode materials are presented. First, the most available preparation methods, such as hydro/solvent thermal, chemical vapor deposition, and electrodeposition, are summarized. Then, the unique performance of metal telluride electrodes in capacitors, anode materials of Li/Na ion batteries, electrocatalysis, and lithium-sulfur batteries are discussed. Finally, significant challenges and opportunities in the preparation and application of 2D metal tellurides are proposed.
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Affiliation(s)
| | - Shaonan Gu
- *Correspondence: Shaonan Gu, ; Guowei Zhou,
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12
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Fortin-Deschênes M, Pu R, Zhou YF, Ma C, Cheung P, Watanabe K, Taniguchi T, Zhang F, Du X, Xia F. Uncovering Topological Edge States in Twisted Bilayer Graphene. NANO LETTERS 2022; 22:6186-6193. [PMID: 35900257 DOI: 10.1021/acs.nanolett.2c01481] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Twisted bilayer graphene (t-BLG) has recently been introduced as a rich physical platform displaying flat electronic bands, strongly correlated states, and unconventional superconductivity. Studies have hinted at an unusual Z2 topology of the moiré Dirac bands of t-BLG. However, direct experimental evidence of this moiré band topology and associated edge states is still lacking. Herein, using superconducting quantum interferometry, we reconstructed the spatial supercurrent distribution in t-BLG Josephson junctions and revealed the presence of edge states located in the superlattice band gaps. The absence of edge conduction in high resistance regions just outside the superlattice band gap confirms that the edge transport originates from the filling of electronic states located inside the band gap and further allows us to exclude several other edge conduction mechanisms. These results confirm the unusual moiré band topology of twisted bilayer graphene and will stimulate further research to explore its consequences.
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Affiliation(s)
| | - Rui Pu
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, United States
| | - Yan-Feng Zhou
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 7508, United States
| | - Chao Ma
- Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, United States
| | - Patrick Cheung
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 7508, United States
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Fan Zhang
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 7508, United States
| | - Xu Du
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, United States
| | - Fengnian Xia
- Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, United States
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13
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Vergniory MG, Wieder BJ, Elcoro L, Parkin SSP, Felser C, Bernevig BA, Regnault N. All topological bands of all nonmagnetic stoichiometric materials. Science 2022; 376:eabg9094. [PMID: 35587971 DOI: 10.1126/science.abg9094] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Topological quantum chemistry and symmetry-based indicators have facilitated large-scale searches for materials with topological properties at the Fermi energy (EF). We report the implementation of a publicly accessible catalog of stable and fragile topology in all of the bands both at and away from EF in the 96,196 processable entries in the Inorganic Crystal Structure Database. Our calculations, which represent the completion of the symmetry-indicated band topology of known nonmagnetic materials, have enabled the discovery of repeat-topological and supertopological materials, including rhombohedral bismuth and Bi2Mg3. We find that 52.65% of all materials are topological at EF, roughly two-thirds of bands across all materials exhibit symmetry-indicated stable topology, and 87.99% of all materials contain at least one stable or fragile topological band.
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Affiliation(s)
- Maia G Vergniory
- Donostia International Physics Center, 20018 Donostia-San Sebastian, Spain.,IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.,Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Benjamin J Wieder
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.,Department of Physics, Northeastern University, Boston, MA 02115, USA.,Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - Luis Elcoro
- Department of Condensed Matter Physics, University of the Basque Country UPV/EHU, 48080 Bilbao, Spain
| | - Stuart S P Parkin
- Max Planck Institute of Microstructure Physics, 06120 Halle, Germany
| | - Claudia Felser
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - B Andrei Bernevig
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - Nicolas Regnault
- Department of Physics, Princeton University, Princeton, NJ 08544, USA.,Laboratoire de Physique de l'École Normale Supérieure, PSL University, CNRS, Sorbonne Université, Université Paris Diderot, Sorbonne Paris Cité, Paris, France
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14
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The field-free Josephson diode in a van der Waals heterostructure. Nature 2022; 604:653-656. [PMID: 35478238 DOI: 10.1038/s41586-022-04504-8] [Citation(s) in RCA: 53] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 02/02/2022] [Indexed: 11/08/2022]
Abstract
The superconducting analogue to the semiconducting diode, the Josephson diode, has long been sought with multiple avenues to realization being proposed by theorists1-3. Showing magnetic-field-free, single-directional superconductivity with Josephson coupling, it would serve as the building block for next-generation superconducting circuit technology. Here we realized the Josephson diode by fabricating an inversion symmetry breaking van der Waals heterostructure of NbSe2/Nb3Br8/NbSe2. We demonstrate that even without a magnetic field, the junction can be superconducting with a positive current while being resistive with a negative current. The ΔIc behaviour (the difference between positive and negative critical currents) with magnetic field is symmetric and Josephson coupling is proved through the Fraunhofer pattern. Also, stable half-wave rectification of a square-wave excitation was achieved with a very low switching current density, high rectification ratio and high robustness. This non-reciprocal behaviour strongly violates the known Josephson relations and opens the door to discover new mechanisms and physical phenomena through integration of quantum materials with Josephson junctions, and provides new avenues for superconducting quantum devices.
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15
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Wang AQ, Xiang PZ, Zhao TY, Liao ZM. Topological nature of higher-order hinge states revealed by spin transport. Sci Bull (Beijing) 2022; 67:788-793. [DOI: 10.1016/j.scib.2022.02.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 12/16/2021] [Accepted: 02/07/2022] [Indexed: 12/01/2022]
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16
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Baumgartner C, Fuchs L, Costa A, Reinhardt S, Gronin S, Gardner GC, Lindemann T, Manfra MJ, Faria Junior PE, Kochan D, Fabian J, Paradiso N, Strunk C. Supercurrent rectification and magnetochiral effects in symmetric Josephson junctions. NATURE NANOTECHNOLOGY 2022; 17:39-44. [PMID: 34795437 DOI: 10.1038/s41565-021-01009-9] [Citation(s) in RCA: 54] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 08/16/2021] [Indexed: 05/28/2023]
Abstract
Transport is non-reciprocal when not only the sign, but also the absolute value of the current depends on the polarity of the applied voltage. It requires simultaneously broken inversion and time-reversal symmetries, for example, by an interplay of spin-orbit coupling and magnetic field. Hitherto, observation of nonreciprocity was tied to resistivity, and dissipationless non-reciprocal circuit elements were elusive. Here we engineer fully superconducting non-reciprocal devices based on highly transparent Josephson junctions fabricated on InAs quantum wells. We demonstrate supercurrent rectification far below the transition temperature. By measuring Josephson inductance, we can link the non-reciprocal supercurrent to an asymmetry of the current-phase relation, and directly derive the supercurrent magnetochiral anisotropy coefficient. A semiquantitative model explains well the main features of our experimental data. Non-reciprocal Josephson junctions have the potential to become for superconducting circuits what pn junctions are for traditional electronics, enabling new non-dissipative circuit elements.
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Affiliation(s)
- Christian Baumgartner
- Institut für Experimentelle und Angewandte Physik, University of Regensburg, Regensburg, Germany
| | - Lorenz Fuchs
- Institut für Experimentelle und Angewandte Physik, University of Regensburg, Regensburg, Germany
| | - Andreas Costa
- Institut für Theoretische Physik, University of Regensburg, Regensburg, Germany
| | - Simon Reinhardt
- Institut für Experimentelle und Angewandte Physik, University of Regensburg, Regensburg, Germany
| | - Sergei Gronin
- Microsoft Quantum Purdue, Purdue University, West Lafayette, IN, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, USA
| | - Geoffrey C Gardner
- Microsoft Quantum Purdue, Purdue University, West Lafayette, IN, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, USA
| | - Tyler Lindemann
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, USA
- Department of Physics and Astronomy, Purdue University, West Lafayette, IN, USA
| | - Michael J Manfra
- Microsoft Quantum Purdue, Purdue University, West Lafayette, IN, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, IN, USA
- Department of Physics and Astronomy, Purdue University, West Lafayette, IN, USA
- School of Materials Engineering, Purdue University, West Lafayette, IN, USA
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, USA
| | | | - Denis Kochan
- Institut für Theoretische Physik, University of Regensburg, Regensburg, Germany
| | - Jaroslav Fabian
- Institut für Theoretische Physik, University of Regensburg, Regensburg, Germany
| | - Nicola Paradiso
- Institut für Experimentelle und Angewandte Physik, University of Regensburg, Regensburg, Germany.
| | - Christoph Strunk
- Institut für Experimentelle und Angewandte Physik, University of Regensburg, Regensburg, Germany
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17
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Higher-order topological insulator in cubic semiconductor quantum wells. Sci Rep 2021; 11:21060. [PMID: 34702881 PMCID: PMC8548307 DOI: 10.1038/s41598-021-00577-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Accepted: 10/07/2021] [Indexed: 11/30/2022] Open
Abstract
The search for exotic new topological states of matter in widely accessible materials, for which the manufacturing process is mastered, is one of the major challenges of the current topological physics. Here we predict higher order topological insulator state in quantum wells based on the most common semiconducting materials. By successively deriving the bulk and boundary Hamiltonians, we theoretically prove the existence of topological corner states due to cubic symmetry in quantum wells with double band inversion. We show that the appearance of corner states does not depend solely on the crystallographic orientation of the meeting edges, but also on the growth orientation of the quantum well. Our theoretical results significantly extend the application potential of topological quantum wells based on IV, II–VI and III–V semiconductors with diamond or zinc-blende structures.
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18
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Adhikari R, Adhikari S, Faina B, Terschanski M, Bork S, Leimhofer C, Cinchetti M, Bonanni A. Positive Magnetoresistance and Chiral Anomaly in Exfoliated Type-II Weyl Semimetal Td-WTe 2. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:2755. [PMID: 34685198 PMCID: PMC8541530 DOI: 10.3390/nano11102755] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 10/06/2021] [Accepted: 10/10/2021] [Indexed: 11/17/2022]
Abstract
Layered van der Waals semimetallic Td-WTe2, exhibiting intriguing properties which include non-saturating extreme positive magnetoresistance (MR) and tunable chiral anomaly, has emerged as a model topological type-II Weyl semimetal system. Here, ∼45 nm thick mechanically exfoliated flakes of Td-WTe2 are studied via atomic force microscopy, Raman spectroscopy, low-T/high-μ0H magnetotransport measurements and optical reflectivity. The contribution of anisotropy of the Fermi liquid state to the origin of the large positive transverse MR⊥ and the signature of chiral anomaly of the type-II Weyl Fermions are reported. The samples are found to be stable in air and no oxidation or degradation of the electronic properties is observed. A transverse MR⊥∼1200 % and an average carrier mobility of 5000 cm2V-1s-1 at T=5K for an applied perpendicular field μ0H⊥=7T are established. The system follows a Fermi liquid model for T≤50K and the anisotropy of the Fermi surface is concluded to be at the origin of the observed positive MR. Optical reflectivity measurements confirm the anisotropy of the electronic behaviour. The relative orientation of the crystal axes and of the applied electric and magnetic fields is proven to determine the observed chiral anomaly in the in-plane magnetotransport. The observed chiral anomaly in the WTe2 flakes is found to persist up to T=120K, a temperature at least four times higher than the ones reported to date.
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Affiliation(s)
- Rajdeep Adhikari
- Institut für Halbleiter-und-Festkörperphysik, Johannes Kepler University, Altenbergerstr. 69, A-4040 Linz, Austria; (S.A.); (B.F.)
| | - Soma Adhikari
- Institut für Halbleiter-und-Festkörperphysik, Johannes Kepler University, Altenbergerstr. 69, A-4040 Linz, Austria; (S.A.); (B.F.)
| | - Bogdan Faina
- Institut für Halbleiter-und-Festkörperphysik, Johannes Kepler University, Altenbergerstr. 69, A-4040 Linz, Austria; (S.A.); (B.F.)
| | - Marc Terschanski
- Department of Physics, TU Dortmund, Otto-Hahn-Straße 4, 44227 Dortmund, Germany; (M.T.); (S.B.); (M.C.)
| | - Sophie Bork
- Department of Physics, TU Dortmund, Otto-Hahn-Straße 4, 44227 Dortmund, Germany; (M.T.); (S.B.); (M.C.)
| | - Claudia Leimhofer
- Institut für Polymerwissenschaften, Johannes Kepler University, Altenbergerstr. 69, A-4040 Linz, Austria;
| | - Mirko Cinchetti
- Department of Physics, TU Dortmund, Otto-Hahn-Straße 4, 44227 Dortmund, Germany; (M.T.); (S.B.); (M.C.)
| | - Alberta Bonanni
- Institut für Halbleiter-und-Festkörperphysik, Johannes Kepler University, Altenbergerstr. 69, A-4040 Linz, Austria; (S.A.); (B.F.)
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19
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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: 27] [Impact Index Per Article: 9.0] [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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20
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Aharon-Steinberg A, Marguerite A, Perello DJ, Bagani K, Holder T, Myasoedov Y, Levitov LS, Geim AK, Zeldov E. Long-range nontopological edge currents in charge-neutral graphene. Nature 2021; 593:528-534. [PMID: 34040212 DOI: 10.1038/s41586-021-03501-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 03/26/2021] [Indexed: 11/09/2022]
Abstract
Van der Waals heterostructures display numerous unique electronic properties. Nonlocal measurements, wherein a voltage is measured at contacts placed far away from the expected classical flow of charge carriers, have been widely used in the search for novel transport mechanisms, including dissipationless spin and valley transport1-9, topological charge-neutral currents10-12, hydrodynamic flows13 and helical edge modes14-16. Monolayer1-5,10,15-19, bilayer9,11,14,20 and few-layer21 graphene, transition-metal dichalcogenides6,7 and moiré superlattices8,10,12 have been found to display pronounced nonlocal effects. However, the origin of these effects is hotly debated3,11,17,22-24. Graphene, in particular, exhibits giant nonlocality at charge neutrality1,15-19, a striking behaviour that has attracted competing explanations. Using a superconducting quantum interference device on a tip (SQUID-on-tip) for nanoscale thermal and scanning gate imaging25, here we demonstrate that the commonly occurring charge accumulation at graphene edges23,26-31 leads to giant nonlocality, producing narrow conductive channels that support long-range currents. Unexpectedly, although the edge conductance has little effect on the current flow in zero magnetic field, it leads to field-induced decoupling between edge and bulk transport at moderate fields. The resulting giant nonlocality at charge neutrality and away from it produces exotic flow patterns that are sensitive to edge disorder, in which charges can flow against the global electric field. The observed one-dimensional edge transport is generic and nontopological and is expected to support nonlocal transport in many electronic systems, offering insight into the numerous controversies and linking them to long-range guided electronic states at system edges.
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Affiliation(s)
- A Aharon-Steinberg
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - A Marguerite
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - D J Perello
- National Graphene Institute and School of Physics and Astronomy, The University of Manchester, Manchester, UK
| | - K Bagani
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - T Holder
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Y Myasoedov
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - L S Levitov
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - A K Geim
- National Graphene Institute and School of Physics and Astronomy, The University of Manchester, Manchester, UK
| | - E Zeldov
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel.
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21
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Qiu D, Gong C, Wang S, Zhang M, Yang C, Wang X, Xiong J. Recent Advances in 2D Superconductors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2006124. [PMID: 33768653 DOI: 10.1002/adma.202006124] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 10/22/2020] [Indexed: 06/12/2023]
Abstract
The emergence of superconductivity in 2D materials has attracted much attention and there has been rapid development in recent years because of their fruitful physical properties, such as high transition temperature (Tc ), continuous phase transition, and enhanced parallel critical magnetic field (Bc ). Tremendous efforts have been devoted to exploring different physical parameters to figure out the mechanisms behind the unexpected superconductivity phenomena, including adjusting the thickness of samples, fabricating various heterostructures, tuning the carrier density by electric field and chemical doping, and so on. Here, different types of 2D superconductivity with their unique characteristics are introduced, including the conventional Bardeen-Cooper-Schrieffer superconductivity in ultrathin films, high-Tc superconductivity in Fe-based and Cu-based 2D superconductors, unconventional superconductivity in newly discovered twist-angle bilayer graphene, superconductivity with enhanced Bc , and topological superconductivity. A perspective toward this field is then proposed based on academic knowledge from the recently reported literature. The aim is to provide researchers with a clear and comprehensive understanding about the newly developed 2D superconductivity and promote the development of this field much further.
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Affiliation(s)
- Dong Qiu
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Chuanhui Gong
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - SiShuang Wang
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Miao Zhang
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Chao Yang
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Xianfu Wang
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Jie Xiong
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
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22
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Choi YB, Xie Y, Chen CZ, Park J, Song SB, Yoon J, Kim BJ, Taniguchi T, Watanabe K, Kim J, Fong KC, Ali MN, Law KT, Lee GH. Evidence of higher-order topology in multilayer WTe 2 from Josephson coupling through anisotropic hinge states. NATURE MATERIALS 2020; 19:974-979. [PMID: 32632280 DOI: 10.1038/s41563-020-0721-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 06/01/2020] [Indexed: 06/11/2023]
Abstract
Td-WTe2 (non-centrosymmetric and orthorhombic), a type-II Weyl semimetal, is expected to have higher-order topological phases with topologically protected, helical one-dimensional hinge states when its Weyl points are annihilated. However, the detection of these hinge states is difficult due to the semimetallic behaviour of the bulk. In this study, we have spatially resolved the hinge states by analysing the magnetic field interference of the supercurrent in Nb-WTe2-Nb proximity Josephson junctions. The Josephson current along the a axis of the WTe2 crystal, but not along the b axis, showed a sharp enhancement at the edges of the junction, and the amount of enhanced Josephson current was comparable to the upper limits of a single one-dimensional helical channel. Our experimental observations suggest a higher-order topological phase in WTe2 and its corresponding anisotropic topological hinge states, in agreement with theoretical calculations. Our work paves the way for the study of hinge states in topological transition-metal dichalcogenides and analogous phases.
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Affiliation(s)
- Yong-Bin Choi
- Department of Physics, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Yingming Xie
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Chui-Zhen Chen
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
- Institute for Advanced Study and School of Physical Science and Technology, Soochow University, Suzhou, China
| | - Jinho Park
- Department of Physics, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Su-Beom Song
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Jiho Yoon
- Max Plank Institute for Microstructure Physics, Halle (Saale), Germany
| | - B J Kim
- Department of Physics, Pohang University of Science and Technology, Pohang, Republic of Korea
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang, Republic of Korea
| | - Takashi Taniguchi
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki, Japan
| | - Jonghwan Kim
- Department of Physics, Pohang University of Science and Technology, Pohang, Republic of Korea
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Kin Chung Fong
- Raytheon BBN Technologies, Quantum Information Processing Group, Cambridge, MA, USA.
| | - Mazhar N Ali
- Max Plank Institute for Microstructure Physics, Halle (Saale), Germany.
| | - Kam Tuen Law
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
| | - Gil-Ho Lee
- Department of Physics, Pohang University of Science and Technology, Pohang, Republic of Korea.
- Asia Pacific Center for Theoretical Physics, Pohang, Republic of Korea.
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23
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Huang C, Narayan A, Zhang E, Xie X, Ai L, Liu S, Yi C, Shi Y, Sanvito S, Xiu F. Edge superconductivity in multilayer WTe 2 Josephson junction. Natl Sci Rev 2020; 7:1468-1475. [PMID: 34691543 PMCID: PMC8288511 DOI: 10.1093/nsr/nwaa114] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 05/21/2020] [Accepted: 05/21/2020] [Indexed: 11/14/2022] Open
Abstract
WTe2, as a type-II Weyl semimetal, has 2D Fermi arcs on the (001) surface in the bulk and 1D helical edge states in its monolayer. These features have recently attracted wide attention in condensed matter physics. However, in the intermediate regime between the bulk and monolayer, the edge states have not been resolved owing to its closed band gap which makes the bulk states dominant. Here, we report the signatures of the edge superconductivity by superconducting quantum interference measurements in multilayer WTe2 Josephson junctions and we directly map the localized supercurrent. In thick WTe2 ([Formula: see text], the supercurrent is uniformly distributed by bulk states with symmetric Josephson effect ([Formula: see text]). In thin WTe2 (10 nm), however, the supercurrent becomes confined to the edge and its width reaches up to [Formula: see text]and exhibits non-symmetric behavior [Formula: see text]. The ability to tune the edge domination by changing thickness and the edge superconductivity establishes WTe2 as a promising topological system with exotic quantum phases and a rich physics.
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Affiliation(s)
- Ce Huang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | | | - Enze Zhang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Xiaoyi Xie
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Linfeng Ai
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Shanshan Liu
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Changjiang Yi
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Youguo Shi
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Stefano Sanvito
- School of Physics, AMBER and CRANN Institute, Trinity College, Dublin 2, Ireland
| | - Faxian Xiu
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
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