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Li Q, Mo SK, Edmonds MT. Recent progress of MnBi 2Te 4 epitaxial thin films as a platform for realising the quantum anomalous Hall effect. NANOSCALE 2024; 16:14247-14260. [PMID: 39015951 DOI: 10.1039/d4nr00194j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/18/2024]
Abstract
Since the first realisation of the quantum anomalous Hall effect (QAHE) in a dilute magnetic-doped topological insulator thin film in 2013, the quantisation temperature has been limited to less than 1 K due to magnetic disorder in dilute magnetic systems. With magnetic moments ordered into the crystal lattice, the intrinsic magnetic topological insulator MnBi2Te4 has the potential to eliminate or significantly reduce magnetic disorder and improve the quantisation temperature. Surprisingly, to date, the QAHE has yet to be observed in molecular beam epitaxy (MBE)-grown MnBi2Te4 thin films at zero magnetic field, and what leads to the difficulty in quantisation is still an active research area. Although bulk MnBi2Te4 and exfoliated flakes have been well studied, revealing both the QAHE and axion insulator phases, experimental progress on MBE thin films has been slower. Understanding how the breakdown of the QAHE occurs in MnBi2Te4 thin films and finding solutions that will enable mass-produced millimetre-size QAHE devices operating at elevated temperatures are required. In this mini-review, we will summarise recent studies on the electronic and magnetic properties of MBE MnBi2Te4 thin films and discuss mechanisms that could explain the failure of the QAHE from the aspects of defects, electronic structure, magnetic order, and consequences of their delicate interplay. Finally, we propose several strategies for realising the QAHE at elevated temperatures in MnBi2Te4 thin films.
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Affiliation(s)
- Qile Li
- School of Physics and Astronomy, Monash University, Clayton, VIC, Australia.
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, VIC, Australia
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Mark T Edmonds
- School of Physics and Astronomy, Monash University, Clayton, VIC, Australia.
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, VIC, Australia
- ANFF-VIC Technology Fellow, Melbourne Centre for Nanofabrication, Victorian Node of the Australian National Fabrication Facility, Clayton, VIC 3168, Australia
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2
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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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3
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Lu Z, Hou S, Lin R, Shi J, Wu Q, Lin L, Shi J, Yang Y, Lambert C, Hong W. Conductance Quantization in 2D Semi-Metallic Transition Metal Dichalcogenides. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2311491. [PMID: 38682729 DOI: 10.1002/smll.202311491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Revised: 03/09/2024] [Indexed: 05/01/2024]
Abstract
Conductance quantization of 2D materials is significant for understanding the charge transport at the atomic scale, which provides a platform to manipulate the quantum states, showing promising applications for nanoelectronics and memristors. However, the conventional methods for investigating conductance quantization are only applicable to materials consisting of one element, such as metal and graphene. The experimental observation of conductance quantization in transition metal dichalcogenides (TMDCs) with complex compositions and structures remains a challenge. To address this issue, an approach is proposed to characterize the charge transport across a single atom in TMDCs by integrating in situ synthesized 1T'-WTe2 electrodes with scanning tunneling microscope break junction (STM-BJ) technique. The quantized conductance of 1T'-WTe2 is measured for the first time, and the quantum states can be modulated by stretching speed and solvent. Combined with theoretical calculations, the evolution of quantized and corresponding configurations during the break junction process is demonstrated. This work provides a facile and reliable avenue to characterize and modulate conductance quantization of 2D materials, intensively expanding the research scope of quantum effects in diverse materials.
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Affiliation(s)
- Zhixing Lu
- Engineering Research Center of Polymer Green Recycling of Ministry of Education, College of Environmental and Resource Sciences, Fujian Normal University, Fuzhou, 350117, China
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering & Pen-Tung Sah Institute of Micro-Nano Science and Technology, Xiamen University, Xiamen, 361005, China
| | - Songjun Hou
- Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK
| | - Rongjian Lin
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering & Pen-Tung Sah Institute of Micro-Nano Science and Technology, Xiamen University, Xiamen, 361005, China
| | - Jie Shi
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering & Pen-Tung Sah Institute of Micro-Nano Science and Technology, Xiamen University, Xiamen, 361005, China
| | - Qingqing Wu
- Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK
| | - Luchun Lin
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering & Pen-Tung Sah Institute of Micro-Nano Science and Technology, Xiamen University, Xiamen, 361005, China
| | - Jia Shi
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering & Pen-Tung Sah Institute of Micro-Nano Science and Technology, Xiamen University, Xiamen, 361005, China
| | - Yang Yang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering & Pen-Tung Sah Institute of Micro-Nano Science and Technology, Xiamen University, Xiamen, 361005, China
| | - Colin Lambert
- Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK
| | - Wenjing Hong
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering & Pen-Tung Sah Institute of Micro-Nano Science and Technology, Xiamen University, Xiamen, 361005, China
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4
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Llopez A, Leroy F, Tagne-Kaegom C, Croes B, Michon A, Mastropasqua C, Al Khalfioui M, Curiotto S, Müller P, Saùl A, Kierren B, Kremer G, Fèvre PL, Bertran F, Fagot-Revurat Y, Cheynis F. Van der Waals Epitaxy of Weyl-Semimetal T d-WTe 2. ACS APPLIED MATERIALS & INTERFACES 2024. [PMID: 38597601 DOI: 10.1021/acsami.4c00676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2024]
Abstract
Epitaxial growth of WTe2 offers significant advantages, including the production of high-quality films, possible long-range in-plane ordering, and precise control over layer thicknesses. However, the mean island size of WTe2 grown by molecular beam epitaxy (MBE) in the literature is only a few tens of nanometers, which is not suitable for the implementation of devices at large lateral scales. Here we report the growth of Td -WTe2 ultrathin films by MBE on monolayer (ML) graphene, reaching a mean flake size of ≃110 nm, which is, on overage, more than three times larger than previous results. WTe2 films thicker than 5 nm have been successfully synthesized and exhibit the expected Td phase atomic structure. We rationalize the epitaxial growth of Td-WTe2 and propose a simple model to estimate the mean flake size as a function of growth parameters that can be applied to other transition metal dichalcogenides (TMDCs). Based on nucleation theory and the Kolmogorov-Johnson-Meh-Avrami (KJMA) equation, our analytical model supports experimental data showing a critical coverage of 0.13 ML above which WTe2 nucleation becomes negligible. The quality of monolayer WTe2 films is demonstrated by electronic band structure analysis using angle-resolved photoemission spectroscopy (ARPES), which is in agreement with first-principles calculations performed on free-standing WTe2 and previous reports. We found electron pockets at the Fermi level, indicating a n-type doping of WTe2 with an electron density of n = 2.0 ± 0.5 × 1012 cm-2 for each electron pocket.
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Affiliation(s)
- Alexandre Llopez
- Aix Marseille Univ, CINAM, AMUtech, CNRS, Marseille 13288 France
| | - Frédéric Leroy
- Aix Marseille Univ, CINAM, AMUtech, CNRS, Marseille 13288 France
| | - Calvin Tagne-Kaegom
- Institut Jean Lamour, UMR 7198 CNRS-Université de Lorraine, Campus ARTEM, 2 allée André Guinier, BP 50840, Nancy 54011, France
| | - Boris Croes
- Aix Marseille Univ, CINAM, AMUtech, CNRS, Marseille 13288 France
- Université de Strasbourg, IPCMS, UMR 7504 CNRS, 23 Rue du Loess Bâtiment 69, Strasbourg 67000, France
| | - Adrien Michon
- CRHEA, Université Côte d'Azur CNRS, Rue Bernard Grégory, Valbonne 06560, France
| | - Chiara Mastropasqua
- CRHEA, Université Côte d'Azur CNRS, Rue Bernard Grégory, Valbonne 06560, France
| | | | - Stefano Curiotto
- Aix Marseille Univ, CINAM, AMUtech, CNRS, Marseille 13288 France
| | - Pierre Müller
- Aix Marseille Univ, CINAM, AMUtech, CNRS, Marseille 13288 France
| | - Andrés Saùl
- Aix Marseille Univ, CINAM, AMUtech, CNRS, Marseille 13288 France
| | - Bertrand Kierren
- Institut Jean Lamour, UMR 7198 CNRS-Université de Lorraine, Campus ARTEM, 2 allée André Guinier, BP 50840, Nancy 54011, France
| | - Geoffroy Kremer
- Institut Jean Lamour, UMR 7198 CNRS-Université de Lorraine, Campus ARTEM, 2 allée André Guinier, BP 50840, Nancy 54011, France
| | - Patrick Le Fèvre
- Université Paris-Saclay, Synchrotron SOLEIL, L'Orme des Merisiers, Départementale 128, Saint-Aubin 91190, France
- Univ Rennes, IPR - UMR 6251, CNRS, Rennes F-35000, France
| | - François Bertran
- Université Paris-Saclay, Synchrotron SOLEIL, L'Orme des Merisiers, Départementale 128, Saint-Aubin 91190, France
| | - Yannick Fagot-Revurat
- Institut Jean Lamour, UMR 7198 CNRS-Université de Lorraine, Campus ARTEM, 2 allée André Guinier, BP 50840, Nancy 54011, France
| | - Fabien Cheynis
- Aix Marseille Univ, CINAM, AMUtech, CNRS, Marseille 13288 France
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5
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Hossain MS, Schindler F, Islam R, Muhammad Z, Jiang YX, Cheng ZJ, Zhang Q, Hou T, Chen H, Litskevich M, Casas B, Yin JX, Cochran TA, Yahyavi M, Yang XP, Balicas L, Chang G, Zhao W, Neupert T, Hasan MZ. A hybrid topological quantum state in an elemental solid. Nature 2024; 628:527-533. [PMID: 38600389 DOI: 10.1038/s41586-024-07203-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 02/16/2024] [Indexed: 04/12/2024]
Abstract
Topology1-3 and interactions are foundational concepts in the modern understanding of quantum matter. Their nexus yields three important research directions: (1) the competition between distinct interactions, as in several intertwined phases, (2) the interplay between interactions and topology that drives the phenomena in twisted layered materials and topological magnets, and (3) the coalescence of several topological orders to generate distinct novel phases. The first two examples have grown into major areas of research, although the last example remains mostly unexplored, mainly because of the lack of a material platform for experimental studies. Here, using tunnelling microscopy, photoemission spectroscopy and a theoretical analysis, we unveil a 'hybrid' topological phase of matter in the simple elemental-solid arsenic. Through a unique bulk-surface-edge correspondence, we uncover that arsenic features a conjoined strong and higher-order topology that stabilizes a hybrid topological phase. Although momentum-space spectroscopy measurements show signs of topological surface states, real-space microscopy measurements unravel a unique geometry of topologically induced step-edge conduction channels revealed on various natural nanostructures on the surface. Using theoretical models, we show that the existence of gapless step-edge states in arsenic relies on the simultaneous presence of both a non-trivial strong Z2 invariant and a non-trivial higher-order topological invariant, which provide experimental evidence for hybrid topology. Our study highlights pathways for exploring the interplay of different band topologies and harnessing the associated topological conduction channels in engineered quantum or nano-devices.
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Affiliation(s)
- Md Shafayat Hossain
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, USA.
| | | | - Rajibul Islam
- International Research Centre MagTop, Institute of Physics, Polish Academy of Sciences, Warsaw, Poland
- Department of Physics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Zahir Muhammad
- Hefei Innovation Research Institute, School of Integrated Circuit Science and Engineering, Beihang University, Hefei, P.R. China
| | - Yu-Xiao Jiang
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, USA
| | - Zi-Jia Cheng
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, USA
| | - Qi Zhang
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, USA
| | - Tao Hou
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Hongyu Chen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Maksim Litskevich
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, USA
| | - Brian Casas
- National High Magnetic Field Laboratory, and Physics Department, Florida State University, Tallahassee, FL, USA
| | - Jia-Xin Yin
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, USA
| | - Tyler A Cochran
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, USA
| | - Mohammad Yahyavi
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Xian P Yang
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, USA
| | - Luis Balicas
- National High Magnetic Field Laboratory, and Physics Department, Florida State University, Tallahassee, FL, USA
| | - Guoqing Chang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Weisheng Zhao
- Hefei Innovation Research Institute, School of Integrated Circuit Science and Engineering, Beihang University, Hefei, P.R. China
| | - Titus Neupert
- Department of Physics, University of Zurich, Zurich, Switzerland
| | - M Zahid Hasan
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, USA.
- Princeton Institute for Science and Technology of Materials, Princeton University, Princeton, NJ, USA.
- Quantum Science Center (QSC, ORNL), Oak Ridge, TN, USA.
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6
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Dufresne SKY, Zhdanovich S, Michiardi M, Guislain BG, Zonno M, Mazzotti V, O'Brien L, Kung S, Levy G, Mills AK, Boschini F, Jones DJ, Damascelli A. A versatile laser-based apparatus for time-resolved ARPES with micro-scale spatial resolution. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2024; 95:033907. [PMID: 38517258 DOI: 10.1063/5.0176170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Accepted: 02/28/2024] [Indexed: 03/23/2024]
Abstract
We present the development of a versatile apparatus for 6.2 eV laser-based time and angle-resolved photoemission spectroscopy with micrometer spatial resolution (time-resolved μ-ARPES). With a combination of tunable spatial resolution down to ∼11 μm, high energy resolution (∼11 meV), near-transform-limited temporal resolution (∼280 fs), and tunable 1.55 eV pump fluence up to 3 mJ/cm2, this time-resolved μ-ARPES system enables the measurement of ultrafast electron dynamics in exfoliated and inhomogeneous materials. We demonstrate the performance of our system by correlating the spectral broadening of the topological surface state of Bi2Se3 with the spatial dimension of the probe pulse, as well as resolving the spatial inhomogeneity contribution to the observed spectral broadening. Finally, after in situ exfoliation, we performed time-resolved μ-ARPES on a ∼30 μm flake of transition metal dichalcogenide WTe2, thus demonstrating the ability to access ultrafast electron dynamics with momentum resolution on micro-exfoliated materials.
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Affiliation(s)
- S K Y Dufresne
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - S Zhdanovich
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - M Michiardi
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - B G Guislain
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - M Zonno
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - V Mazzotti
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - L O'Brien
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - S Kung
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - G Levy
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - A K Mills
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - F Boschini
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Centre Énergie Matériaux Télécommunications, Institut National de la Recherche Scientifique, Varennes, Québec J3X 1S2, Canada
| | - D J Jones
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - A Damascelli
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
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7
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Chen Z, Ding Z, Wang M, Yu P, Yang K, Sun Y, Wang P, Wang Y, Shi F, Bao X, Du J. A convenient and robust design for diamond-based scanning probe microscopes. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2023; 94:113703. [PMID: 37947500 DOI: 10.1063/5.0174744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2023] [Accepted: 10/19/2023] [Indexed: 11/12/2023]
Abstract
Nitrogen-vacancy centers in diamond have been developed as a sensitive magnetic sensor and broadly applied on condensed matter physics. We present a design of a scanning probe microscope based on a nitrogen-vacancy center that can operate under various experimental conditions, including a broad temperature range (20-500 K) and a high-vacuum condition (1 × 10-7 mbar). The design of a compact and robust scanning head and vacuum chamber system is presented, which ensures system stability while enabling the convenience of equipment operations. By showcasing the temperature control performance and presenting confocal images of a single-layer graphene and a diamond probe, along with images of a ferromagnetic strip and an epitaxial BiFeO3 film on the SrTiO3 substrate, we demonstrate the reliability of the instrument. Our study proposes a method and a corresponding design for this microscope that extends its potential applications in nanomagnetism and spintronics.
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Affiliation(s)
- Zhousheng Chen
- CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China
- CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
- Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Zhe Ding
- CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Mengqi Wang
- CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China
- CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Pei Yu
- CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China
- CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Kai Yang
- CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China
- CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Yumeng Sun
- CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China
- CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Pengfei Wang
- CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China
- CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Ya Wang
- CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China
- CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Fazhan Shi
- CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China
- CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
- School of Biomedical Engineering and Suzhou Institute for Advanced Research, University of Science and Technology of China, Suzhou 215123, China
| | - Xinhe Bao
- Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Jiangfeng Du
- CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China
- CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
- School of Physics, Zhejiang University, Hangzhou 310027, China
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8
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Wu S, Fei Z, Sun Z, Yi Y, Xia W, Yan D, Guo Y, Shi Y, Yan J, Cobden DH, Liu WT, Xu X, Wu S. Extrinsic Nonlinear Kerr Rotation in Topological Materials under a Magnetic Field. ACS NANO 2023; 17:18905-18913. [PMID: 37767802 DOI: 10.1021/acsnano.3c04153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/29/2023]
Abstract
Topological properties in quantum materials are often governed by symmetry and tuned by crystal structure and external fields, and hence, symmetry-sensitive nonlinear optical measurements in a magnetic field are a valuable probe. Here, we report nonlinear magneto-optical second harmonic generation (SHG) studies of nonmagnetic topological materials including bilayer WTe2, monolayer WSe2, and bulk TaAs. The polarization-resolved patterns of optical SHG under a magnetic field show nonlinear Kerr rotation in these time-reversal symmetric materials. For materials with 3-fold rotational symmetric lattice structure, the SHG polarization pattern rotates just slightly in a magnetic field, whereas in those with mirror or 2-fold rotational symmetry, the SHG polarization pattern rotates greatly and distorts. These different magneto-SHG characters can be understood by considering the superposition of the magnetic field-induced time-noninvariant nonlinear optical tensor and the crystal-structure-based time-invariant counterpart. The situation is further clarified by scrutinizing the Faraday rotation, whose subtle interplay with crystal symmetry accounts for the diverse behavior of the extrinsic nonlinear Kerr rotation in different materials. Our work illustrates the application of magneto-SHG techniques to directly probe nontrivial topological properties, and underlines the importance of minimizing extrinsic nonlinear Kerr rotation in polarization-resolved magneto-optical studies.
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Affiliation(s)
- Shuang Wu
- State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (MOE), and Department of Physics, Fudan University, Shanghai 200433, China
| | - Zaiyao Fei
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Zeyuan Sun
- State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (MOE), and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yangfan Yi
- State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (MOE), and Department of Physics, Fudan University, Shanghai 200433, China
| | - Wei Xia
- School of Physical Science and Technology, and ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, Shanghai 201210, China
| | - Dayu Yan
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yanfeng Guo
- School of Physical Science and Technology, and ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, Shanghai 201210, China
| | - Youguo Shi
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Jiaqiang Yan
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - David H Cobden
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Wei-Tao Liu
- State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (MOE), and Department of Physics, Fudan University, Shanghai 200433, China
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, United States
| | - Shiwei Wu
- State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (MOE), and Department of Physics, Fudan University, Shanghai 200433, China
- Shanghai Qi Zhi Institute, Shanghai 200232, China
- Institute for Nanoelectronic Devices and Quantum Computing, and Zhangjiang Fudan International Innovation Center, Fudan University, Shanghai 200433, China
- Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
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9
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Rizzo DJ, Zhang J, Jessen BS, Ruta FL, Cothrine M, Yan J, Mandrus DG, Nagler SE, Taniguchi T, Watanabe K, Fogler MM, Pasupathy AN, Millis AJ, Rubio A, Hone JC, Dean CR, Basov DN. Polaritonic Probe of an Emergent 2D Dipole Interface. NANO LETTERS 2023; 23:8426-8435. [PMID: 37494638 DOI: 10.1021/acs.nanolett.3c01611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/28/2023]
Abstract
The use of work-function-mediated charge transfer has recently emerged as a reliable route toward nanoscale electrostatic control of individual atomic layers. Using α-RuCl3 as a 2D electron acceptor, we are able to induce emergent nano-optical behavior in hexagonal boron nitride (hBN) that arises due to interlayer charge polarization. Using scattering-type scanning near-field optical microscopy (s-SNOM), we find that a thin layer of α-RuCl3 adjacent to an hBN slab reduces the propagation length of hBN phonon polaritons (PhPs) in significant excess of what can be attributed to intrinsic optical losses. Concomitant nano-optical spectroscopy experiments reveal a novel resonance that aligns energetically with the region of excess PhP losses. These experimental observations are elucidated by first-principles density-functional theory and near-field model calculations, which show that the formation of a large interfacial dipole suppresses out-of-plane PhP propagation. Our results demonstrate the potential utility of charge-transfer heterostructures for tailoring optoelectronic properties of 2D insulators.
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Affiliation(s)
- Daniel J Rizzo
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Jin Zhang
- Theory Department, Max Planck Institute for Structure and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
| | - Bjarke S Jessen
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Francesco L Ruta
- Department of Physics, Columbia University, New York, New York 10027, United States
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Matthew Cothrine
- 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 G 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
| | - Stephen E Nagler
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Michael M Fogler
- Department of Physics, University of California San Diego, La Jolla, California 92093, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Andrew J Millis
- Department of Physics, Columbia University, New York, New York 10027, United States
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, United States
| | - Angel Rubio
- Theory Department, Max Planck Institute for Structure and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, United States
- Nano-Bio Spectroscopy Group, Universidad del País Vasco UPV/EHU, San Sebastián 20018, Spain
| | - James C 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
| | - D N Basov
- Department of Physics, Columbia University, New York, New York 10027, United States
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10
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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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11
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Oskoui Abdol S, Shojaei S, Abdollahipour B. Polarization dependent light propagation in [Formula: see text] multilayer structure. Sci Rep 2023; 13:13169. [PMID: 37580415 PMCID: PMC10425423 DOI: 10.1038/s41598-023-40460-7] [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: 04/24/2023] [Accepted: 08/10/2023] [Indexed: 08/16/2023] Open
Abstract
[Formula: see text] is one of the exciting and outstanding semimetallic members of TMDCs, which has attracted immense attention for manipulating light propagation due to its inherent optical anisotropy and hyperbolic characteristic in the infrared frequency range. We investigate the dependence of the reflectance and transmittance of structures with a single and double [Formula: see text] thin film in terms of frequency and polarization angle of the incident wave. We find rich behaviors in the optical response of these structures due to their anisotropic permittivity tensors. Furthermore, we analyze the polarization state of transmitted and reflected waves through these structures. We demonstrate that these structures provide the ability to achieve desired polarization rotation for outgoing waves by tuning the frequency and polarization angle of the incident wave with respect to the principal axes of [Formula: see text] thin film. In particular, we elucidate the essential relevance of the optical response and polarization rotation of the double thin film structure to the in-plain twist angle of [Formula: see text] thin films. We explain that this structure permits comprehensive control of the polarization rotation of the outgoing waves by adjusting the twist angle of thin films. The proposed structure can be employed as an efficient light manipulator with the aim of application in communication, imaging, and information processing.
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Affiliation(s)
- S. Oskoui Abdol
- Faculty of Physics, University of Tabriz, Tabriz, 51666-16471 Iran
- Research Institute for Applied Physics and Astronomy (RIAPA), University of Tabriz, Tabriz, 51655-163 Iran
| | - S. Shojaei
- Faculty of Physics, University of Tabriz, Tabriz, 51666-16471 Iran
- Research Institute for Applied Physics and Astronomy (RIAPA), University of Tabriz, Tabriz, 51655-163 Iran
| | - B. Abdollahipour
- Faculty of Physics, University of Tabriz, Tabriz, 51666-16471 Iran
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12
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Evans PE, Wang Y, Sushko PV, Dohnálek Z. Understanding palladium-tellurium cluster formation on WTe 2: From a kinetically hindered distribution to thermodynamically controlled monodispersity. PNAS NEXUS 2023; 2:pgad212. [PMID: 37416870 PMCID: PMC10321376 DOI: 10.1093/pnasnexus/pgad212] [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: 04/13/2023] [Revised: 06/10/2023] [Accepted: 06/15/2023] [Indexed: 07/08/2023]
Abstract
A fundamental understanding of the transition metal dichalcogenide (TMDC)-metal interface is critical for their utilization in a broad range of applications. We investigate how the deposition of palladium (Pd), as a model metal, on WTe2(001), leads to the assembly of Pd into clusters and nanoparticles. Using X-ray photoemission spectroscopy, scanning tunneling microscopy imaging, and ab initio simulations, we find that Pd nucleation is driven by the interaction with and the availability of mobile excess tellurium (Te) leading to the formation of Pd-Te clusters at room temperature. Surprisingly, the nucleation of Pd-Te clusters is not affected by intrinsic surface defects, even at elevated temperatures. Upon annealing, the Pd-Te nanoclusters adopt an identical nanostructure and are stable up to ∼523 K. Density functional theory calculations provide a foundation for our understanding of the mobility of Pd and Te atoms, preferential nucleation of Pd-Te clusters, and the origin of their annealing-induced monodispersity. These results highlight the role the excess chalcogenide atoms may play in the metal deposition process. More broadly, the discoveries of synthetic pathways yielding thermally robust monodispersed nanostructures on TMDCs are critical to the manufacturing of novel quantum and microelectronics devices and catalytically active nano-alloy centers.
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Affiliation(s)
- Prescott E Evans
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Yang Wang
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
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13
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Grubišić-Čabo A, Michiardi M, Sanders CE, Bianchi M, Curcio D, Phuyal D, Berntsen MH, Guo Q, Dendzik M. In Situ Exfoliation Method of Large-Area 2D Materials. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023:e2301243. [PMID: 37236159 PMCID: PMC10401183 DOI: 10.1002/advs.202301243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Indexed: 05/28/2023]
Abstract
2D materials provide a rich platform to study novel physical phenomena arising from quantum confinement of charge carriers. Many of these phenomena are discovered by surface sensitive techniques, such as photoemission spectroscopy, that work in ultra-high vacuum (UHV). Success in experimental studies of 2D materials, however, inherently relies on producing adsorbate-free, large-area, high-quality samples. The method that yields 2D materials of highest quality is mechanical exfoliation from bulk-grown samples. However, as this technique is traditionally performed in a dedicated environment, the transfer of samples into vacuum requires surface cleaning that might diminish the quality of the samples. In this article, a simple method for in situ exfoliation directly in UHV is reported, which yields large-area, single-layered films. Multiple metallic and semiconducting transition metal dichalcogenides are exfoliated in situ onto Au, Ag, and Ge. The exfoliated flakes are found to be of sub-millimeter size with excellent crystallinity and purity, as supported by angle-resolved photoemission spectroscopy, atomic force microscopy, and low-energy electron diffraction. The approach is well-suited for air-sensitive 2D materials, enabling the study of a new suite of electronic properties. In addition, the exfoliation of surface alloys and the possibility of controlling the substrate-2D material twist angle is demonstrated.
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Affiliation(s)
- Antonija Grubišić-Čabo
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, 9747 AG, The Netherlands
- Department of Applied Physics, KTH Royal Institute of Technology, Hannes Alfvéns väg 12, Stockholm, 114 19, Sweden
| | - Matteo Michiardi
- Quantum Matter Institute, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada
| | - Charlotte E Sanders
- Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, 0X11 0QX, UK
| | - Marco Bianchi
- School of Physics and Astronomy, Aarhus University, Aarhus, 8000 C, Denmark
| | - Davide Curcio
- School of Physics and Astronomy, Aarhus University, Aarhus, 8000 C, Denmark
| | - Dibya Phuyal
- Department of Applied Physics, KTH Royal Institute of Technology, Hannes Alfvéns väg 12, Stockholm, 114 19, Sweden
| | - Magnus H Berntsen
- Department of Applied Physics, KTH Royal Institute of Technology, Hannes Alfvéns väg 12, Stockholm, 114 19, Sweden
| | - Qinda Guo
- Department of Applied Physics, KTH Royal Institute of Technology, Hannes Alfvéns väg 12, Stockholm, 114 19, Sweden
| | - Maciej Dendzik
- Department of Applied Physics, KTH Royal Institute of Technology, Hannes Alfvéns väg 12, Stockholm, 114 19, Sweden
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14
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Bampoulis P, Castenmiller C, Klaassen DJ, van Mil J, Liu Y, Liu CC, Yao Y, Ezawa M, Rudenko AN, Zandvliet HJW. Quantum Spin Hall States and Topological Phase Transition in Germanene. PHYSICAL REVIEW LETTERS 2023; 130:196401. [PMID: 37243643 DOI: 10.1103/physrevlett.130.196401] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Accepted: 03/24/2023] [Indexed: 05/29/2023]
Abstract
We present the first experimental evidence of a topological phase transition in a monoelemental quantum spin Hall insulator. Particularly, we show that low-buckled epitaxial germanene is a quantum spin Hall insulator with a large bulk gap and robust metallic edges. Applying a critical perpendicular electric field closes the topological gap and makes germanene a Dirac semimetal. Increasing the electric field further results in the opening of a trivial gap and disappearance of the metallic edge states. This electric field-induced switching of the topological state and the sizable gap make germanene suitable for room-temperature topological field-effect transistors, which could revolutionize low-energy electronics.
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Affiliation(s)
- Pantelis Bampoulis
- Physics of Interfaces and Nanomaterials, MESA+ Institute, University of Twente, Drienerlolaan 5, 7522 NB, Enschede, Netherlands
| | - Carolien Castenmiller
- Physics of Interfaces and Nanomaterials, MESA+ Institute, University of Twente, Drienerlolaan 5, 7522 NB, Enschede, Netherlands
| | - Dennis J Klaassen
- Physics of Interfaces and Nanomaterials, MESA+ Institute, University of Twente, Drienerlolaan 5, 7522 NB, Enschede, Netherlands
| | - Jelle van Mil
- Physics of Interfaces and Nanomaterials, MESA+ Institute, University of Twente, Drienerlolaan 5, 7522 NB, Enschede, Netherlands
| | - Yichen Liu
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Cheng-Cheng Liu
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Yugui Yao
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Motohiko Ezawa
- Department of Applied Physics, University of Tokyo, Hongo, 113-8656 Tokyo, Japan
| | - Alexander N Rudenko
- Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, Netherlands
| | - Harold J W Zandvliet
- Physics of Interfaces and Nanomaterials, MESA+ Institute, University of Twente, Drienerlolaan 5, 7522 NB, Enschede, Netherlands
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15
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Jiang Z, Chong SK, Zhang P, Deng P, Chu S, Jahanbani S, Wang KL, Lai K. Implementing microwave impedance microscopy in a dilution refrigerator. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2023; 94:2887606. [PMID: 37125853 DOI: 10.1063/5.0138831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 04/11/2023] [Indexed: 05/03/2023]
Abstract
We report the implementation of a dilution refrigerator-based scanning microwave impedance microscope with a base temperature of ∼100 mK. The vibration noise of our apparatus with tuning-fork feedback control is as low as 1 nm. Using this setup, we have demonstrated the imaging of quantum anomalous Hall states in magnetically (Cr and V) doped (Bi, Sb)2Te3 thin films grown on mica substrates. Both the conductive edge modes and topological phase transitions near the coercive fields of Cr- and V-doped layers are visualized in the field-dependent results. Our study establishes the experimental platform for investigating nanoscale quantum phenomena at ultralow temperatures.
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Affiliation(s)
- Zhanzhi Jiang
- Department of Physics, University of Texas at Austin, Austin, Texas 78712, USA
| | - Su Kong Chong
- Department of Electrical and Computer Engineering, University of California, Los Angeles, California 90095, USA
| | - Peng Zhang
- Department of Electrical and Computer Engineering, University of California, Los Angeles, California 90095, USA
| | - Peng Deng
- Department of Electrical and Computer Engineering, University of California, Los Angeles, California 90095, USA
| | - Shizai Chu
- Department of Physics, University of Texas at Austin, Austin, Texas 78712, USA
| | - Shahin Jahanbani
- Department of Physics, University of Texas at Austin, Austin, Texas 78712, USA
| | - Kang L Wang
- Department of Electrical and Computer Engineering, University of California, Los Angeles, California 90095, USA
| | - Keji Lai
- Department of Physics, University of Texas at Austin, Austin, Texas 78712, USA
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16
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Chen W. Optical absorption measurement of spin Berry curvature and spin Chern marker. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 35:155601. [PMID: 36753769 DOI: 10.1088/1361-648x/acba72] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 02/08/2023] [Indexed: 06/18/2023]
Abstract
In two-dimensional time-reversal symmetric topological insulators described by Dirac models, theZ2topological invariant can be described by the spin Chern number. We present a linear response theory for the spin Berry curvature that integrates to the spin Chern number, and introduce its spectral function that can be measured at finite temperature by momentum- and spin-resolved circular dichroism, which may be achieved by pump-probe type of experiments using spin- and time-resolved ARPES. As a result, the sign of the Pfaffian of theZ2invariant can be directly measured. A spin Chern number spectral function is further introduced from the optical spin current response, and is shown to be measurable from the spin-resolved opacity of two-dimensional materials under circularly polarized light, pointing to an optical measurement of theZ2invariant and a frequency sum rule. The spin Chern number expressed in real space is known to yield a spin Chern marker, and we propose that it may be measurable from spin-resolved local heating rate caused by circularly polarized light. A nonlocal spin Chern marker is further proposed to characterize the quantum criticality near topological phase transitions, and is shown to be equivalent to an overlap between spin-selected Wannier states.
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Affiliation(s)
- Wei Chen
- Department of Physics, PUC-Rio, Rio de Janeiro 22451-900, Brazil
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17
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Lin W, Feng Y, Wang Y, Zhu J, Lian Z, Zhang H, Li H, Wu Y, Liu C, Wang Y, Zhang J, Wang Y, Chen CZ, Zhou X, Shen J. Direct visualization of edge state in even-layer MnBi 2Te 4 at zero magnetic field. Nat Commun 2022; 13:7714. [PMID: 36513662 PMCID: PMC9747779 DOI: 10.1038/s41467-022-35482-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 12/06/2022] [Indexed: 12/15/2022] Open
Abstract
Being the first intrinsic antiferromagnetic (AFM) topological insulator (TI), MnBi2Te4 is argued to be a topological axion state in its even-layer form due to the antiparallel magnetization between the top and bottom layers. Here we combine both transport and scanning microwave impedance microscopy (sMIM) to investigate such axion state in atomically thin MnBi2Te4 with even-layer thickness at zero magnetic field. While transport measurements show a zero Hall plateau signaturing the axion state, sMIM uncovers an unexpected edge state raising questions regarding the nature of the "axion state". Based on our model calculation, we propose that the edge state of even-layer MnBi2Te4 at zero field is derived from gapped helical edge states of the quantum spin Hall effect with time-reversal-symmetry breaking, when a crossover from a three-dimensional TI MnBi2Te4 to a two-dimensional TI occurs. Our finding thus signifies the richness of topological phases in MnB2Te4 that has yet to be fully explored.
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Affiliation(s)
- Weiyan Lin
- State Key Laboratory of Surface Physics and Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai, China
| | - Yang Feng
- Department of Physics, Fudan University, Shanghai, China
| | - Yongchao Wang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, China
- Beijing Innovation Center for Future Chips, Tsinghua University, Beijing, China
| | - Jinjiang Zhu
- Department of Physics, Fudan University, Shanghai, China
| | - Zichen Lian
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, China
| | - Huanyu Zhang
- Department of Physics, Fudan University, Shanghai, China
| | - Hao Li
- School of Materials Science and Engineering, Tsinghua University, Beijing, China
- Tsinghua-Foxconn Nanotechnology Research Center, Department of Physics, Tsinghua University, Beijing, China
| | - Yang Wu
- Tsinghua-Foxconn Nanotechnology Research Center, Department of Physics, Tsinghua University, Beijing, China
- Department of Mechanical Engineering, Tsinghua University, Beijing, China
| | - Chang Liu
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, China
- Beijing Academy of Quantum Information Science, Beijing, China
| | - Yihua Wang
- Department of Physics, Fudan University, Shanghai, China
- Shanghai Research Center for Quantum Sciences, Shanghai, China
| | - Jinsong Zhang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, China
- Frontier Science Center for Quantum Information, Beijing, China
| | - Yayu Wang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, China
- Frontier Science Center for Quantum Information, Beijing, China
| | - Chui-Zhen Chen
- School of Physical Science and Technology, Soochow University, Suzhou, China
- Institute for Advanced Study, Soochow University, Suzhou, China
| | - Xiaodong Zhou
- State Key Laboratory of Surface Physics and Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai, China.
- Zhangjiang Fudan International Innovation Center, Fudan University, Shanghai, China.
- Shanghai Qi Zhi Institute, Shanghai, China.
| | - Jian Shen
- State Key Laboratory of Surface Physics and Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai, China.
- Department of Physics, Fudan University, Shanghai, China.
- Zhangjiang Fudan International Innovation Center, Fudan University, Shanghai, China.
- Shanghai Qi Zhi Institute, Shanghai, China.
- Collaborative Innovation Center of Advanced Microstructures, Nanjing, China.
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18
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Zhang G, Wu H, Zhang L, Yang L, Xie Y, Guo F, Li H, Tao B, Wang G, Zhang W, Chang H. Two-Dimensional Van Der Waals Topological Materials: Preparation, Properties, and Device Applications. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2204380. [PMID: 36135779 DOI: 10.1002/smll.202204380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 08/23/2022] [Indexed: 06/16/2023]
Abstract
Over the past decade, 2D van der Waals (vdW) topological materials (TMs), including topological insulators and topological semimetals, which combine atomically flat 2D layers and topologically nontrivial band structures, have attracted increasing attention in condensed-matter physics and materials science. These easily cleavable and integrated TMs provide the ideal platform for exploring topological physics in the 2D limit, where new physical phenomena may emerge, and represent a potential to control and investigate exotic properties and device applications in nanoscale topological phases. However, multifaced efforts are still necessary, which is the prerequisite for the practical application of 2D vdW TMs. Herein, this review focuses on the preparation, properties, and device applications of 2D vdW TMs. First, three common preparation strategies for 2D vdW TMs are summarized, including single crystal exfoliation, chemical vapor deposition, and molecular beam epitaxy. Second, the origin and regulation of various properties of 2D vdW TMs are introduced, involving electronic properties, transport properties, optoelectronic properties, thermoelectricity, ferroelectricity, and magnetism. Third, some device applications of 2D vdW TMs are presented, including field-effect transistors, memories, spintronic devices, and photodetectors. Finally, some significant challenges and opportunities for the practical application of 2D vdW TMs in 2D topological electronics are briefly addressed.
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Affiliation(s)
- Gaojie Zhang
- Quantum-Nano Matter and Device Lab, Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
- Institute for Quantum Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Hao Wu
- Quantum-Nano Matter and Device Lab, Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
- Institute for Quantum Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Liang Zhang
- Liuzhou Key Laboratory for New Energy Vehicle Power Lithium Battery, School of Microelectronics and Engineering, Guangxi University of Science and Technology, Liuzhou, 545006, China
| | - Li Yang
- Quantum-Nano Matter and Device Lab, Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
- Institute for Quantum Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Yuanmiao Xie
- Liuzhou Key Laboratory for New Energy Vehicle Power Lithium Battery, School of Microelectronics and Engineering, Guangxi University of Science and Technology, Liuzhou, 545006, China
| | - Fei Guo
- Liuzhou Key Laboratory for New Energy Vehicle Power Lithium Battery, School of Microelectronics and Engineering, Guangxi University of Science and Technology, Liuzhou, 545006, China
| | - Hongda Li
- Liuzhou Key Laboratory for New Energy Vehicle Power Lithium Battery, School of Microelectronics and Engineering, Guangxi University of Science and Technology, Liuzhou, 545006, China
| | - Boran Tao
- Liuzhou Key Laboratory for New Energy Vehicle Power Lithium Battery, School of Microelectronics and Engineering, Guangxi University of Science and Technology, Liuzhou, 545006, China
| | - Guofu Wang
- Liuzhou Key Laboratory for New Energy Vehicle Power Lithium Battery, School of Microelectronics and Engineering, Guangxi University of Science and Technology, Liuzhou, 545006, China
| | - Wenfeng Zhang
- Quantum-Nano Matter and Device Lab, Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
- Institute for Quantum Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
- Shenzhen R&D Center of Huazhong University of Science and Technology (HUST), Shenzhen, 518000, China
| | - Haixin Chang
- Quantum-Nano Matter and Device Lab, Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
- Institute for Quantum Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
- Shenzhen R&D Center of Huazhong University of Science and Technology (HUST), Shenzhen, 518000, China
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19
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Lu X, Zhou P, Chen S, Sun L. Strain-induced two-dimensional topological insulators in monolayer 1T'-RuO 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:475502. [PMID: 36174549 DOI: 10.1088/1361-648x/ac965b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 09/29/2022] [Indexed: 06/16/2023]
Abstract
Because of their unique structure and novel physical properties, two-dimensional (2D) transition metal dichalcogenides (TMDs) have received a lot of attention in recent years. In this paper, we propose a new 2D TMD 1T'-RuO2with tunable topological properties. Based on first-principles calculations, we demonstrate that it has good dynamics, thermodynamic, energetic stability, and anisotropic mechanical properties. Although 1T'-RuO2is a typical semiconductor with a direct bandgap, it can be transformed into topological insulator by applying uniaxial tensile strains. The topological phase transition is attributed to thed-dband inversion at Γ point. The nontrivial topological property is further validated by the topological edge states. We predict that monolayer 1T'-RuO2is an excellent material for future electronic devices with tunable topological properties.
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Affiliation(s)
- Xin Lu
- School of Material Sciences and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
| | - Pan Zhou
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
| | - Shuhui Chen
- School of Material Sciences and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
| | - Lizhong Sun
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, People's Republic of China
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20
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Li J, Rashetnia M, Lohmann M, Koo J, Xu Y, Zhang X, Watanabe K, Taniguchi T, Jia S, Chen X, Yan B, Cui YT, Shi J. Proximity-magnetized quantum spin Hall insulator: monolayer 1 T' WTe 2/Cr 2Ge 2Te 6. Nat Commun 2022; 13:5134. [PMID: 36050322 PMCID: PMC9436961 DOI: 10.1038/s41467-022-32808-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Accepted: 08/18/2022] [Indexed: 11/20/2022] Open
Abstract
Van der Waals heterostructures offer great versatility to tailor unique interactions at the atomically flat interfaces between dissimilar layered materials and induce novel physical phenomena. By bringing monolayer 1 T’ WTe2, a two-dimensional quantum spin Hall insulator, and few-layer Cr2Ge2Te6, an insulating ferromagnet, into close proximity in an heterostructure, we introduce a ferromagnetic order in the former via the interfacial exchange interaction. The ferromagnetism in WTe2 manifests in the anomalous Nernst effect, anomalous Hall effect as well as anisotropic magnetoresistance effect. Using local electrodes, we identify separate transport contributions from the metallic edge and insulating bulk. When driven by an AC current, the second harmonic voltage responses closely resemble the anomalous Nernst responses to AC temperature gradient generated by nonlocal heater, which appear as nonreciprocal signals with respect to the induced magnetization orientation. Our results from different electrodes reveal spin-polarized edge states in the magnetized quantum spin Hall insulator. Van der Waals heterostructures allow for the integration of several materials with different properties in the one heterostructure. Here, Li et al combine a quantum spin hall insulator, WTe2, with an insulating ferromagnet, Cr2Ge2Te6, in a van der Waals heterostructure, with resulting proximity-induced magnetism in the WTe2 layer leading to an anomalous Hall and Nernst effect.
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Affiliation(s)
- Junxue Li
- Department of Physics and Astronomy, University of California, Riverside, CA, 92521, USA.,Department of Physics, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Mina Rashetnia
- Department of Physics and Astronomy, University of California, Riverside, CA, 92521, USA
| | - Mark Lohmann
- Department of Physics and Astronomy, University of California, Riverside, CA, 92521, USA
| | - Jahyun Koo
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Youming Xu
- Department of Electrical and Computer Engineering, University of California, Riverside, CA, 92521, USA
| | - Xiao Zhang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
| | - 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
| | - Shuang Jia
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
| | - Xi Chen
- Department of Electrical and Computer Engineering, University of California, Riverside, CA, 92521, USA
| | - Binghai Yan
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Yong-Tao Cui
- Department of Physics and Astronomy, University of California, Riverside, CA, 92521, USA
| | - Jing Shi
- Department of Physics and Astronomy, University of California, Riverside, CA, 92521, USA.
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21
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Lüpke F, Waters D, Pham AD, Yan J, Mandrus DG, Ganesh P, Hunt BM. Quantum Spin Hall Edge States and Interlayer Coupling in Twisted Bilayer WTe 2. NANO LETTERS 2022; 22:5674-5680. [PMID: 35759639 DOI: 10.1021/acs.nanolett.2c00432] [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
The quantum spin Hall (QSH) effect, characterized by topologically protected spin-polarized edge states, was recently demonstrated in monolayers of the transition metal dichalcogenide (TMD) WTe2. However, the robustness of this topological protection remains largely unexplored in van der Waals heterostructures containing one or more layers of a QSH insulator. In this work, we use scanning tunneling microscopy and spectroscopy (STM/STS) to explore the topological nature of twisted bilayer (tBL) WTe2. At the tBL edges, we observe the characteristic spectroscopic signatures of the QSH edge states. For small twist angles, a rectangular moiré pattern develops, which results in local modifications of the band structure. Using first-principles calculations, we quantify the interactions in tBL WTe2 and its topological edge states as a function of interlayer distance and conclude that it is possible to engineer the topology of WTe2 bilayers via the twist angle as well as interlayer interactions.
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Affiliation(s)
- Felix Lüpke
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Dacen Waters
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Anh D Pham
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Jiaqiang Yan
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - David G 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
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Panchapakesan Ganesh
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Benjamin M Hunt
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
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22
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Ozdemir I, Holleitner AW, Kastl C, Aktürk OÜ. Thickness and defect dependent electronic, optical and thermoelectric features of [Formula: see text]. Sci Rep 2022; 12:12756. [PMID: 35882909 PMCID: PMC9325696 DOI: 10.1038/s41598-022-16899-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 07/18/2022] [Indexed: 11/08/2022] Open
Abstract
Transition metal dichalcogenides (TMDs) receive significant attention due to their outstanding electronic and optical properties. In this study, we investigate the electronic, optical, and thermoelectric properties of single and few layer [Formula: see text] in detail utilizing first-principles methods based on the density functional theory (DFT). Within the scope of both PBE and HSE06 including spin orbit coupling (SOC), the simulations predict the electronic band gap values to decrease as the number of layers increases. Moreover, spin-polarized DFT calculations combined with the semi-classical Boltzmann transport theory are applied to estimate the anisotropic thermoelectric power factor (Seebeck coefficient, S) for [Formula: see text] in both the monolayer and multilayer limit, and S is obtained below the optimal value for practical applications. The optical absorbance of [Formula: see text] monolayer is obtained to be slightly less than the values reported in literature for 2H TMD monolayers of [Formula: see text], [Formula: see text], and [Formula: see text]. Furthermore, we simulate the impact of defects, such as vacancy, antisite and substitution defects, on the electronic, optical and thermoelectric properties of monolayer [Formula: see text]. Particularly, the Te-[Formula: see text] substitution defect in parallel orientation yields negative formation energy, indicating that the relevant defect may form spontaneously under relevant experimental conditions. We reveal that the electronic band structure of [Formula: see text] monolayer is significantly influenced by the presence of the considered defects. According to the calculated band gap values, a lowering of the conduction band minimum gives rise to metallic characteristics to the structure for the single Te(1) vacancy, a diagonal Te line defect, and the Te(1)-[Formula: see text] substitution, while the other investigated defects cause an opening of a small positive band gap at the Fermi level. Consequently, the real ([Formula: see text]) and imaginary ([Formula: see text]) parts of the dielectric constant at low frequencies are very sensitive to the applied defects, whereas we find that the absorbance (A) at optical frequencies is less significantly affected. We also predict that certain point defects can enhance the otherwise moderate value of S in pristine [Formula: see text] to values relevant for thermoelectric applications. The described [Formula: see text] monolayers, as functionalized with the considered defects, offer the possibility to be applied in optical, electronic, and thermoelectric devices.
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Affiliation(s)
- Ilkay Ozdemir
- Physics Department, Adnan Menderes University, 09100 Aydin, Turkey
| | - Alexander W. Holleitner
- Walter Schottky Institut and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
- Munich Center of Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany
| | - Christoph Kastl
- Walter Schottky Institut and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
- Munich Center of Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany
| | - Olcay Üzengi Aktürk
- Walter Schottky Institut and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
- Electrical Electronics Engineering Department, Adnan Menderes University, 09100 Aydin, Turkey
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23
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Wang P, Yang Y, Pan E, Liu F, Ajayan PM, Zhou J, Liu Z. Emerging Phases of Layered Metal Chalcogenides. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2105215. [PMID: 34923740 DOI: 10.1002/smll.202105215] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Revised: 11/10/2021] [Indexed: 06/14/2023]
Abstract
Layered metal chalcogenides, as a "rich" family of 2D materials, have attracted increasing research interest due to the abundant choices of materials with diverse structures and rich electronic characteristics. Although the common metal chalcogenide phases such as 2H and 1T have been intensively studied, many other unusual phases are rarely explored, and some of these show fascinating behaviors including superconductivity, ferroelectrics, ferromagnetism, etc. From this perspective, the unusual phases of metal chalcogenides and their characteristics, as well as potential applications are introduced. First, the unusual phases of metal chalcogenides from different classes, including transition metal dichalcogenides, magnetic element-based chalcogenides, and metal phosphorus chalcogenides, are discussed, respectively. Meanwhile, their excellent properties of different unusual phases are introduced. Then, the methods for producing the unusual phases are discussed, specifically, the stabilization strategies during the chemical vapor deposition process for the unusual phase growth are discussed, followed by an outlook and discussions on how to prepare the unusual phase metal dichalcogenides in terms of synthetic methodology and potential applications.
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Affiliation(s)
- Ping Wang
- Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), Beijing Key Lab of Nanophotonics, and Ultrafine Optoelectronic Systems, and School of Physics, School of Physics, Beijing Institute of Technology, Beijing, 100081, China
| | - Yang Yang
- Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), Beijing Key Lab of Nanophotonics, and Ultrafine Optoelectronic Systems, and School of Physics, School of Physics, Beijing Institute of Technology, Beijing, 100081, China
| | - Er Pan
- School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 610054, China
- Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou, 313099, China
| | - Fucai Liu
- School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 610054, China
- Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou, 313099, China
| | - Pulickel M Ajayan
- Department of Materials Science and Nano Engineering, Rice University, Houston, TX, 77005, USA
| | - Jiadong Zhou
- Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), Beijing Key Lab of Nanophotonics, and Ultrafine Optoelectronic Systems, and School of Physics, School of Physics, Beijing Institute of Technology, Beijing, 100081, China
| | - Zheng Liu
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
- School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798, Singapore
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24
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Kitamura M, Souma S, Honma A, Wakabayashi D, Tanaka H, Toyoshima A, Amemiya K, Kawakami T, Sugawara K, Nakayama K, Yoshimatsu K, Kumigashira H, Sato T, Horiba K. Development of a versatile micro-focused angle-resolved photoemission spectroscopy system with Kirkpatrick-Baez mirror optics. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:033906. [PMID: 35364976 DOI: 10.1063/5.0074393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 02/28/2022] [Indexed: 06/14/2023]
Abstract
Angle-resolved photoemission spectroscopy using a micro-focused beam spot [micro-angle-resolved photoemission spectroscopy (ARPES)] is becoming a powerful tool to elucidate key electronic states of exotic quantum materials. We have developed a versatile micro-ARPES system based on the synchrotron radiation beam focused with a Kirkpatrick-Baez mirror optics. The mirrors are monolithically installed on a stage, which is driven with five-axis motion, and are vibrationally separated from the ARPES measurement system. Spatial mapping of the Au photolithography pattern on Si signifies the beam spot size of 10 µm (horizontal) × 12 µm (vertical) at the sample position, which is well suited to resolve the fine structure in local electronic states. Utilization of the micro-beam and the high precision sample motion system enables the accurate spatially resolved band-structure mapping, as demonstrated by the observation of a small band anomaly associated with tiny sample bending near the edge of a cleaved topological insulator single crystal.
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Affiliation(s)
- Miho Kitamura
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Seigo Souma
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
| | - Asuka Honma
- Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Daisuke Wakabayashi
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Hirokazu Tanaka
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Akio Toyoshima
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Kenta Amemiya
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Tappei Kawakami
- Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Katsuaki Sugawara
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
| | - Kosuke Nakayama
- Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Kohei Yoshimatsu
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai 980-8577, Japan
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Takafumi Sato
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
| | - Koji Horiba
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
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25
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Zhu J, Li T, Young AF, Shan J, Mak KF. Quantum Oscillations in Two-Dimensional Insulators Induced by Graphite Gates. PHYSICAL REVIEW LETTERS 2021; 127:247702. [PMID: 34951797 DOI: 10.1103/physrevlett.127.247702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 11/04/2021] [Indexed: 06/14/2023]
Abstract
We demonstrate a mechanism for magnetoresistance oscillations in insulating states of two-dimensional (2D) materials arising from the interaction of the 2D layer and proximal graphite gates. We study a series of devices based on different 2D systems, including mono- and bilayer T_{d}-WTe_{2}, MoTe_{2}/WSe_{2} moiré heterobilayers, and Bernal-stacked bilayer graphene, which all share a similar graphite-gated geometry. We find that the 2D systems, when tuned near an insulating state, generically exhibit magnetoresistance oscillations corresponding to a high-density Fermi surface, in contravention of naïve band theory. Simultaneous measurement of the resistivity of the graphite gates shows that the oscillations of the sample layer are precisely correlated with those of the graphite gates. Further supporting this connection, the oscillations are quenched when the graphite gate is replaced by a low-mobility metal, TaSe_{2}. The observed phenomenon arises from the oscillatory behavior of graphite density of states, which modulates the device capacitance and, as a consequence, the carrier density in the sample layer even when a constant electrochemical potential is maintained between the sample and the gate electrode. Oscillations are most pronounced near insulating states where the resistivity is strongly density dependent. Our study suggests a unified mechanism for quantum oscillations in graphite-gated 2D insulators based on electrostatic sample-gate coupling.
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Affiliation(s)
- Jiacheng Zhu
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - Tingxin Li
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - Andrea F Young
- Department of Physics, University of California, Santa Barbara, California 93106, USA
| | - Jie Shan
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
| | - Kin Fai Mak
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
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26
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Xu M, Tang B, Lu Y, Zhu C, Lu Q, Zhu C, Zheng L, Zhang J, Han N, Fang W, Guo Y, Di J, Song P, He Y, Kang L, Zhang Z, Zhao W, Guan C, Wang X, Liu Z. Machine Learning Driven Synthesis of Few-Layered WTe 2 with Geometrical Control. J Am Chem Soc 2021; 143:18103-18113. [PMID: 34606266 DOI: 10.1021/jacs.1c06786] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Reducing the lateral scale of two-dimensional (2D) materials to one-dimensional (1D) has attracted substantial research interest not only to achieve competitive electronic applications but also for the exploration of fundamental physical properties. Controllable synthesis of high-quality 1D nanoribbons (NRs) is thus highly desirable and essential for further study. Here, we report the implementation of supervised machine learning (ML) for the chemical vapor deposition (CVD) synthesis of high-quality quasi-1D few-layered WTe2 NRs. Feature importance analysis indicates that H2 gas flow rate has a profound influence on the formation of WTe2, and the source ratio governs the sample morphology. Notably, the growth mechanism of 1T' few-layered WTe2 NRs is further proposed, which provides new insights for the growth of intriguing 2D and 1D tellurides and may inspire the growth strategies for other 1D nanostructures. Our findings suggest the effectiveness and capability of ML in guiding the synthesis of 1D nanostructures, opening up new opportunities for intelligent materials development.
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Affiliation(s)
- Manzhang Xu
- School of Information Science and Technology, Northwest University, Xi'an 710127, P. R. China.,Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China.,MIIT Key Laboratory of Flexible Electronics (KLoFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China.,Shaanxi Key Laboratory of Flexible Electronics (KLoFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China
| | - Bijun Tang
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Yuhao Lu
- School of Computer Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Chao Zhu
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Qianbo Lu
- Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China.,MIIT Key Laboratory of Flexible Electronics (KLoFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China.,Shaanxi Key Laboratory of Flexible Electronics (KLoFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China
| | - Chao Zhu
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Lu Zheng
- Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China.,MIIT Key Laboratory of Flexible Electronics (KLoFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China.,Shaanxi Key Laboratory of Flexible Electronics (KLoFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China
| | - Jingyu Zhang
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Nannan Han
- Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China.,MIIT Key Laboratory of Flexible Electronics (KLoFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China.,Shaanxi Key Laboratory of Flexible Electronics (KLoFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China
| | - Weidong Fang
- State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, P. R. China
| | - Yuxi Guo
- School of Information Science and Technology, Northwest University, Xi'an 710127, P. R. China
| | - Jun Di
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Pin Song
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Yongmin He
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, P. R. China
| | - Lixing Kang
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Zhiyong Zhang
- School of Information Science and Technology, Northwest University, Xi'an 710127, P. R. China
| | - Wu Zhao
- School of Information Science and Technology, Northwest University, Xi'an 710127, P. R. China
| | - Cuntai Guan
- School of Computer Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Xuewen Wang
- Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China.,MIIT Key Laboratory of Flexible Electronics (KLoFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China.,Shaanxi Key Laboratory of Flexible Electronics (KLoFE), Northwestern Polytechnical University, Xi'an 710072, P. R. China
| | - Zheng Liu
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.,CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno Plaza, 50 Nanyang Drive, Border X Block, Level 6, Singapore 637553, Singapore.,School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
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27
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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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28
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Jing R, Shao Y, Fei Z, Lo CFB, Vitalone RA, Ruta FL, Staunton J, Zheng WJC, Mcleod AS, Sun Z, Jiang BY, Chen X, Fogler MM, Millis AJ, Liu M, Cobden DH, Xu X, Basov DN. Terahertz response of monolayer and few-layer WTe 2 at the nanoscale. Nat Commun 2021; 12:5594. [PMID: 34552072 PMCID: PMC8458490 DOI: 10.1038/s41467-021-23933-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 05/17/2021] [Indexed: 02/08/2023] Open
Abstract
Tungsten ditelluride (WTe2) is an atomically layered transition metal dichalcogenide whose physical properties change systematically from monolayer to bilayer and few-layer versions. In this report, we use apertureless scattering-type near-field optical microscopy operating at Terahertz (THz) frequencies and cryogenic temperatures to study the distinct THz range electromagnetic responses of mono-, bi- and trilayer WTe2 in the same multi-terraced micro-crystal. THz nano-images of monolayer terraces uncovered weakly insulating behavior that is consistent with transport measurements. The near-field signal on bilayer regions shows moderate metallicity with negligible temperature dependence. Subdiffractional THz imaging data together with theoretical calculations involving thermally activated carriers favor the semimetal scenario with [Formula: see text] over the semiconductor scenario for bilayer WTe2. Also, we observed clear metallic behavior of the near-field signal on trilayer regions. Our data are consistent with the existence of surface plasmon polaritons in the THz range confined to trilayer terraces in our specimens. Finally, data for microcrystals up to 12 layers thick reveal how the response of a few-layer WTe2 asymptotically approaches the bulk limit.
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Affiliation(s)
- Ran Jing
- Department of Physics, Columbia University, New York, NY, USA.
| | - Yinming Shao
- Department of Physics, Columbia University, New York, NY, USA
| | - Zaiyao Fei
- Department of Physics, University of Washington, Seattle, WA, USA
| | | | | | - Francesco L Ruta
- Department of Physics, Columbia University, New York, NY, USA
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA
| | - John Staunton
- Department of Physics, Columbia University, New York, NY, USA
| | | | | | - Zhiyuan Sun
- Department of Physics, Columbia University, New York, NY, USA
| | - Bor-Yuan Jiang
- Department of Physics, University of California, San Diego, La Jolla, CA, USA
| | - Xinzhong Chen
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
| | - Michael M Fogler
- Department of Physics, University of California, San Diego, La Jolla, CA, USA
| | - Andrew J Millis
- Department of Physics, Columbia University, New York, NY, USA
- Center for Computational Quantum Physics, Flatiron Institute, New York, NY, USA
| | - Mengkun Liu
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, USA
| | - David H Cobden
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, USA
- Department of Material Science and Engineering, University of Washington, Seattle, WA, USA
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, USA
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29
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Zhang Y, Devakul T, Fu L. Spin-textured Chern bands in AB-stacked transition metal dichalcogenide bilayers. Proc Natl Acad Sci U S A 2021; 118:e2112673118. [PMID: 34475221 PMCID: PMC8433558 DOI: 10.1073/pnas.2112673118] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 07/29/2021] [Indexed: 11/18/2022] Open
Abstract
While transition-metal dichalcogenide (TMD)-based moiré materials have been shown to host various correlated electronic phenomena, topological states have not been experimentally observed until now [T. Li et al., Quantum anomalous Hall effect from intertwined moiré bands. arXiv [Preprint] (2021). https://arxiv.org/abs/2107.01796 (Accessed 5 July 2021)]. In this work, using first-principle calculations and continuum modeling, we reveal the displacement field-induced topological moiré bands in AB-stacked TMD heterobilayer [Formula: see text]/[Formula: see text] Valley-contrasting Chern bands with nontrivial spin texture are formed from interlayer hybridization between [Formula: see text] and [Formula: see text] bands of nominally opposite spins. Our study establishes a recipe for creating topological bands in AB-stacked TMD bilayers in general, which provides a highly tunable platform for realizing quantum-spin Hall and interaction-induced quantum anomalous Hall effects.
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Affiliation(s)
- Yang Zhang
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Trithep Devakul
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139
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30
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Lu Z, Prange MP, Sushko PV. Tuning Electronic Properties of 2D Materials Using Metal Adsorbates: Cu at WTe 2 Edges. J Phys Chem Lett 2021; 12:6596-6603. [PMID: 34251220 DOI: 10.1021/acs.jpclett.1c01617] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Two-dimensional materials exhibit properties promising for novel applications. Topologically protected states at their edges can be harnessed for use in quantum devices. We use ab initio simulations to examine properties of edges in 1T'-WTe2 monolayers, known to exhibit topological order, and their interactions with Cu atoms. Comparison of (010)-oriented edges that have the same composition but different terminations shows that, as the number of Cu atoms increases, their thermodynamically preferred arrangement depends on the details of the edge structure. Cu atoms aggregate into a cluster at the most stable edge; while the cluster is nonmagnetic, it spin-polarizes the W atoms along the edge, which removes the topological protection. At the metastable edge, Cu atoms form a chain incorporated into the WTe2 lattice; the topological state is preserved in spite of the dramatic edge restructuring. This suggests that exploiting interactions of metal species with metastable edge terminations can provide a path toward noninvasive interfaces.
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Affiliation(s)
- Zexi Lu
- Physical Sciences Division, Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Micah P Prange
- Physical Sciences Division, Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Peter V Sushko
- Physical Sciences Division, Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
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31
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Sonner MM, Khosravi F, Janker L, Rudolph D, Koblmüller G, Jacob Z, Krenner HJ. Ultrafast electron cycloids driven by the transverse spin of a surface acoustic wave. SCIENCE ADVANCES 2021; 7:eabf7414. [PMID: 34321198 PMCID: PMC8318372 DOI: 10.1126/sciadv.abf7414] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 06/11/2021] [Indexed: 06/01/2023]
Abstract
Spin-momentum locking is a universal wave phenomenon promising for applications in electronics and photonics. In acoustics, Lord Rayleigh showed that surface acoustic waves exhibit a characteristic elliptical particle motion strikingly similar to spin-momentum locking. Although these waves have become one of the few phononic technologies of industrial relevance, the observation of their transverse spin remained an open challenge. Here, we observe the full spin dynamics by detecting ultrafast electron cycloids driven by the gyrating electric field produced by a surface acoustic wave propagating on a slab of lithium niobate. A tubular quantum well wrapped around a nanowire serves as an ultrafast sensor tracking the full cyclic motion of electrons. Our acousto-optoelectrical approach opens previously unknown directions in the merged fields of nanoacoustics, nanophotonics, and nanoelectronics for future exploration.
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Affiliation(s)
- Maximilian M Sonner
- Lehrstuhl für Experimentalphysik 1, Institut für Physik, Universität Augsburg, Universitätsstraße 1, 86159 Augsburg, Germany
| | - Farhad Khosravi
- Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G 1H9, Canada
- Birck Nanotechnology Center, School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47906, USA
| | - Lisa Janker
- Lehrstuhl für Experimentalphysik 1, Institut für Physik, Universität Augsburg, Universitätsstraße 1, 86159 Augsburg, Germany
| | - Daniel Rudolph
- Walter Schottky Institut and Physik Department E24, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Gregor Koblmüller
- Walter Schottky Institut and Physik Department E24, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Zubin Jacob
- Birck Nanotechnology Center, School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47906, USA.
| | - Hubert J Krenner
- Physikalisches Institut, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany.
- Lehrstuhl für Experimentalphysik 1, Institut für Physik, Universität Augsburg, Universitätsstraße 1, 86159 Augsburg, Germany
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32
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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: 16] [Impact Index Per Article: 5.3] [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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33
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Longuinhos R, Vymazalová A, Cabral AR, Ribeiro-Soares J. Raman spectrum of layered tilkerodeite (Pd 2HgSe 3) topological insulator: the palladium analogue of jacutingaite (Pt 2HgSe 3). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:065401. [PMID: 33086198 DOI: 10.1088/1361-648x/abc35a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The layered mineral tilkerodeite (Pd2HgSe3), the palladium analogue of jacutingaite (Pt2HgSe3), is a promising quantum spin hall insulator for low-power nanospintronics. In this context, a fast and reliable assessment of its structure is key for exploring fundamental properties and architecture of new Pd2HgSe3-based devices. Here, we investigate the first-order Raman spectrum in high-quality, single-crystal bulk tilkerodeite, and analyze the wavenumber relation to its isostructural jacutingaite analogue. By using polarized Raman spectroscopy, symmetry analysis, and first-principles calculations, we assigned all the Raman-active phonons in tilkerodeite, unveiling their wavenumbers, atomic displacement patterns, and symmetries. Our calculations used several exchange-correlation functionals within the density functional perturbation theory framework, reproducing both structure and Raman-active phonon wavenumbers in excellent agreement with experiments. Also, it was found that the influence of the spin-orbit coupling can be neglected in the study of these properties. Finally, we compared the wavenumber and atomic displacement patterns of corresponding Raman-active modes in tilkerodeite and jacutingaite, and found that the effect of the Pd and Pt masses can be neglected on reasoning their wavenumber differences. From this analysis, tilkerodeite is found to be mechanically weaker than jacutingaite against the atomic displacement patterns of these modes. Our findings advance the understanding of the structural properties of a recently discovered layered topological insulator, fundamental to further exploring its electronic, optical, thermal, and mechanical properties, and for device fabrication.
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Affiliation(s)
- R Longuinhos
- Departamento de Física, Universidade Federal de Lavras, Lavras, MG, 37200-000, Brazil
| | - A Vymazalová
- Department of Rock Geochemistry, Czech Geological Survey, Geologická 6, 152 00 Prague 5, Czech Republic
| | - A R Cabral
- Centro de Pesquisa Professor Manoel Teixeira da Costa, Instituto de Geociências, Universidade Federal de Minas Gerais (UFMG), 31270-901 Belo Horizonte, MG, Brazil
- Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), 31270-901 Belo Horizonte, MG, Brazil
| | - J Ribeiro-Soares
- Departamento de Física, Universidade Federal de Lavras, Lavras, MG, 37200-000, Brazil
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34
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Chen W, Hu M, Zong J, Xie X, Meng Q, Yu F, Wang L, Ren W, Chen A, Liu G, Xi X, Li FS, Sun J, Liu J, Zhang Y. Epitaxial Growth of Single-Phase 1T'-WSe 2 Monolayer with Assistance of Enhanced Interface Interaction. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2004930. [PMID: 33382156 DOI: 10.1002/adma.202004930] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 11/16/2020] [Indexed: 06/12/2023]
Abstract
The WSe2 monolayer in 1T' phase is reported to be a large-gap quantum spin Hall insulator, but is thermodynamically metastable and so far the fabricated samples have always been in the mixed phase of 1T' and 2H, which has become a bottleneck for further exploration and potential applications of the nontrivial topological properties. Based on first-principle calculations in this work, it is found that the 1T' phase could be more stable than 2H phase with enhanced interface interactions. Inspired by this discovery, SrTiO3 (100) is chosen as substrate and WSe2 monolayer is successfully grown in a 100% single 1T' phase using the molecular beam epitaxial method. Combining in situ scanning tunneling microscopy and angle-resolved photoemission spectroscopy measurements, it is found that the in-plane compressive strain in the interface drives the 1T'-WSe2 into a semimetallic phase. Besides providing a new material platform for topological states, the results show that the interface interaction is a new approach to control both the structure phase stability and the topological band structures of transition metal dichalcogenides.
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Affiliation(s)
- Wang Chen
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Mengli Hu
- Department of Physics, Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Hong Kong, China
| | - Junyu Zong
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Xuedong Xie
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Qinghao Meng
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Fan Yu
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Li Wang
- Vacuum Interconnected Nanotech Workstation (Nano-X), Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou, 215123, China
| | - Wei Ren
- Vacuum Interconnected Nanotech Workstation (Nano-X), Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou, 215123, China
| | - Aixi Chen
- Vacuum Interconnected Nanotech Workstation (Nano-X), Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou, 215123, China
| | - Gan Liu
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Xiaoxiang Xi
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing, 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Fang-Sen Li
- Vacuum Interconnected Nanotech Workstation (Nano-X), Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou, 215123, China
| | - Jian Sun
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing, 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Junwei Liu
- Department of Physics, Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Hong Kong, China
| | - Yi Zhang
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing, 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
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35
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Garcia JH, Vila M, Hsu CH, Waintal X, Pereira VM, Roche S. Canted Persistent Spin Texture and Quantum Spin Hall Effect in WTe_{2}. PHYSICAL REVIEW LETTERS 2020; 125:256603. [PMID: 33416383 DOI: 10.1103/physrevlett.125.256603] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 10/02/2020] [Accepted: 11/12/2020] [Indexed: 06/12/2023]
Abstract
We report an unconventional quantum spin Hall phase in the monolayer WTe_{2}, which exhibits hitherto unknown features in other topological materials. The low symmetry of the structure induces a canted spin texture in the yz plane, which dictates the spin polarization of topologically protected boundary states. Additionally, the spin Hall conductivity gets quantized (2e^{2}/h) with a spin quantization axis parallel to the canting direction. These findings are based on large-scale quantum simulations of the spin Hall conductivity tensor and nonlocal resistances in multiprobe geometries using a realistic tight-binding model elaborated from first-principle methods. The observation of this canted quantum spin Hall effect, related to the formation of topological edge states with nontrivial spin polarization, demands for specific experimental design and suggests interesting alternatives for manipulating spin information in topological materials.
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Affiliation(s)
- Jose H Garcia
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Marc Vila
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
- Department of Physics, Universitat Autònoma de Barcelona, Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Chuang-Han Hsu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore
| | - Xavier Waintal
- Université Grenoble Alpes, CEA, IRIG-PHELIQS, 38000 Grenoble, France
| | - Vitor M Pereira
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575
| | - Stephan Roche
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
- ICREA-Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain
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36
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Patlatiuk T, Scheller CP, Hill D, Tserkovnyak Y, Egues JC, Barak G, Yacoby A, Pfeiffer LN, West KW, Zumbühl DM. Edge-State Wave Functions from Momentum-Conserving Tunneling Spectroscopy. PHYSICAL REVIEW LETTERS 2020; 125:087701. [PMID: 32909808 DOI: 10.1103/physrevlett.125.087701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 07/21/2020] [Indexed: 06/11/2023]
Abstract
We perform momentum-conserving tunneling spectroscopy using a GaAs cleaved-edge overgrowth quantum wire to investigate adjacent quantum Hall edge states. We use the lowest five wire modes with their distinct wave functions to probe each edge state and apply magnetic fields to modify the wave functions and their overlap. This reveals an intricate and rich tunneling conductance fan structure which is succinctly different for each of the wire modes. We self-consistently solve the Poisson-Schrödinger equations to simulate the spectroscopy, reproducing the striking fans in great detail, thus, confirming the calculations. Further, the model predicts hybridization between wire states and Landau levels, which is also confirmed experimentally. This establishes momentum-conserving tunneling spectroscopy as a powerful technique to probe edge state wave functions.
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Affiliation(s)
- T Patlatiuk
- Departement Physik, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - C P Scheller
- Departement Physik, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - D Hill
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Y Tserkovnyak
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - J C Egues
- Instituto de Física de São Carlos, Universidade de São Paulo, 13560-970 São Carlos, São Paulo, Brazil
| | - G Barak
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - A Yacoby
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - L N Pfeiffer
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - K W West
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - D M Zumbühl
- Departement Physik, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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37
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Ma C, Wang Q, Mills S, Chen X, Deng B, Yuan S, Li C, Watanabe K, Taniguchi T, Du X, Zhang F, Xia F. Moiré Band Topology in Twisted Bilayer Graphene. NANO LETTERS 2020; 20:6076-6083. [PMID: 32692566 DOI: 10.1021/acs.nanolett.0c02131] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Recently twisted bilayer graphene (t-BLG) has emerged as a strongly correlated physical platform. Besides the apparent significance of band flatness, band topology may be another critical element in t-BLG and yet receives much less attention. Here we report the compelling evidence for nontrivial noninteracting Moiré band topology in t-BLG through a systematic nonlocal transport study and a K-theory examination. The nontrivial topology manifests itself as two pronounced nonlocal responses in the electron and hole superlattice gaps. We show that the nonlocal responses are robust to the twist angle and edge termination, exhibiting a universal scaling law. We elucidate that, although Berry curvature is symmetry-trivialized, two nontrivial Z2 invariants characterize the Moiré Dirac bands, validating the topological origin of the observed nonlocal responses. Our findings not only provide a new perspective for understanding the strongly correlated t-BLG but also suggest a potential strategy to achieve topological metamaterials from trivial vdW materials.
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Affiliation(s)
- Chao Ma
- Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, United States
| | - Qiyue Wang
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 7508, United States
| | - Scott Mills
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, United States
| | - Xiaolong Chen
- Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, United States
| | - Bingchen Deng
- Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, United States
| | - Shaofan Yuan
- Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, United States
| | - Cheng Li
- Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, United States
| | - 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
| | - Xu Du
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, United States
| | - Fan Zhang
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 7508, United States
| | - Fengnian Xia
- Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, United States
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38
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Kim HW, Kang SH, Kim HJ, Chae K, Cho S, Ko W, Jeon S, Kang SH, Yang H, Kim SW, Park S, Hwang S, Kwon YK, Son YW. Symmetry Dictated Grain Boundary State in a Two-Dimensional Topological Insulator. NANO LETTERS 2020; 20:5837-5843. [PMID: 32628851 DOI: 10.1021/acs.nanolett.0c01756] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Grain boundaries (GBs) are ubiquitous in solids and have been of central importance in understanding the nature of polycrystals. In addition to their classical roles, topological insulators (TIs) offer a chance to realize GBs hosting distinct topological states that can be controlled by their crystal symmetries. However, such roles of crystalline symmetry in two-dimensional (2D) TIs have not been definitively measured yet. Here, we present the first direct evidence of a symmetry-enforced metallic state along a GB in 1T'-MoTe2, a prototypical 2D TI. Using scanning tunneling microscopy, we show a metallic state along a GB with nonsymmorphic lattice symmetry and its absence along another boundary with symmorphic symmetry. Our atomistic simulations demonstrate in-gap Weyl semimetallic states for the former, whereas they demonstrate gapped states for the latter, explaining our observation well. The observed metallic state, tightly linked to its crystal symmetry, can be used to create a stable conducting nanowire inside TIs.
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Affiliation(s)
- Hyo Won Kim
- Samsung Advanced Institute of Technology, Suwon 13595, Korea
| | | | - Hyun-Jung Kim
- Korea Institute for Advanced Study, Seoul 02455, Korea
| | - Kisung Chae
- Korea Institute for Advanced Study, Seoul 02455, Korea
| | - Suyeon Cho
- Division of Chemical Engineering and Materials Science, Ewha Womans University, Seoul 03760, Korea
| | - Wonhee Ko
- Samsung Advanced Institute of Technology, Suwon 13595, Korea
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Sangjun Jeon
- Department of Physics, Chung-ang University, Seoul 06987, Korea
| | - Se Hwang Kang
- Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Korea
| | - Heejun Yang
- Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Korea
| | - Sung Wng Kim
- Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Korea
| | - Seongjun Park
- Samsung Advanced Institute of Technology, Suwon 13595, Korea
| | - Sungwoo Hwang
- Samsung Advanced Institute of Technology, Suwon 13595, Korea
| | - Young-Kyun Kwon
- Korea Institute for Advanced Study, Seoul 02455, Korea
- Department of Physics and Research Institute for Basic Sciences, Kyung Hee University, Seoul 02447, Korea
| | - Young-Woo Son
- Korea Institute for Advanced Study, Seoul 02455, Korea
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39
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Wu YJ, Hou J, Li YM, Luo XW, Shi X, Zhang C. In-Plane Zeeman-Field-Induced Majorana Corner and Hinge Modes in an s-Wave Superconductor Heterostructure. PHYSICAL REVIEW LETTERS 2020; 124:227001. [PMID: 32567912 DOI: 10.1103/physrevlett.124.227001] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Accepted: 05/18/2020] [Indexed: 06/11/2023]
Abstract
Second-order topological superconductors host Majorana corner and hinge modes in contrast to conventional edge and surface modes in two and three dimensions. However, the realization of such second-order corner modes usually demands unconventional superconducting pairing or complicated junctions or layered structures. Here we show that Majorana corner modes could be realized using a 2D quantum spin Hall insulator in proximity contact with an s-wave superconductor and subject to an in-plane Zeeman field. Beyond a critical value, the in-plane Zeeman field induces opposite effective Dirac masses between adjacent boundaries, leading to one Majorana mode at each corner. A similar paradigm also applies to 3D topological insulators with the emergence of Majorana hinge states. Avoiding complex superconductor pairing and material structure, our scheme provides an experimentally realistic platform for implementing Majorana corner and hinge states.
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Affiliation(s)
- Ya-Jie Wu
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA
- School of Science, Xi'an Technological University, Xi'an 710032, China
| | - Junpeng Hou
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA
| | - Yun-Mei Li
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA
| | - Xi-Wang Luo
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA
| | - Xiaoyan Shi
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA
| | - Chuanwei Zhang
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA
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40
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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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41
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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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42
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Hu X, Wong KP, Zeng L, Guo X, Liu T, Zhang L, Chen Q, Zhang X, Zhu Y, Fung KH, Lau SP. Infrared Nanoimaging of Surface Plasmons in Type-II Dirac Semimetal PtTe 2 Nanoribbons. ACS NANO 2020; 14:6276-6284. [PMID: 32374588 DOI: 10.1021/acsnano.0c02466] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Topological Dirac semimetals made of two-dimensional transition-metal dichalcogenides (TMDCs) have attracted enormous interest for use in electronic and optoelectronic devices because of their electron transport properties. As van der Waals materials with a strong interlayer interaction, these semimetals are expected to support layer-dependent plasmonic polaritons yet to be revealed experimentally. Here, we demonstrate the apparent retardation and attenuation of mid-infrared (MIR) plasmonic waves in type-II Dirac semimetal platinum tellurium (PtTe2) nanoribbons and nanoflakes by near-field nanoimaging. The attenuated dispersion relations for the plasmonic modes in the PtTe2 nanoribbons (15-25 nm thick) extracted from the near-field standing-wave patterns are applied for the fitting of PtTe2 permittivity in the MIR regime, indicating that both free carriers and Dirac fermions are involved in MIR light-matter interaction in PtTe2. The annihilation of plasmonic modes in the ultrathin (<10 nm) PtTe2 is observed and analyzed, which manifests no near-field resonant pattern due to the intrinsic layer-dependent optoelectronic properties of PtTe2. These results could pave a potential wave for MIR photodetection and modulation with TMDC semimetals.
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Affiliation(s)
- Xin Hu
- Institute of Advanced Magnetic Materials, Hangzhou Dianzi University, Hangzhou 310012, China
- Department of Computing, The Hong Kong Polytechnic University, Hong Kong S.A.R., China
| | - Kin Ping Wong
- Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong S.A.R., China
| | - Longhui Zeng
- Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong S.A.R., China
| | - Xuyun Guo
- Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong S.A.R., China
| | - Tong Liu
- Vacuum Interconnected Nanotech Workstation (NANO-X), Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
| | - Lei Zhang
- Department of Computing, The Hong Kong Polytechnic University, Hong Kong S.A.R., China
| | - Qin Chen
- Institute of Nanophotonics, Jinan University, Guangzhou 511443, China
| | - Xuefeng Zhang
- Institute of Advanced Magnetic Materials, Hangzhou Dianzi University, Hangzhou 310012, China
| | - Ye Zhu
- Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong S.A.R., China
| | - Kin Hung Fung
- Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong S.A.R., China
| | - Shu Ping Lau
- Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong S.A.R., China
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43
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Li Z, Song Y, Tang S. Quantum spin Hall state in monolayer 1T '-TMDCs. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:333001. [PMID: 32244235 DOI: 10.1088/1361-648x/ab8660] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 04/03/2020] [Indexed: 06/11/2023]
Abstract
Although the 1T'phase is rare in the transition metal dichalcogenides (TMDCs) family, it has attracted rapid growing research interest due to the coexistence of superconductivity, unsaturated magneto-resistance, topological phases etc. Among them, the quantum spin Hall (QSH) state in monolayer 1T'-TMDCs is especially interesting because of its unique van der Waals crystal structure, bringing advantages in the fundamental research and application. For example, the van der Waals two-dimensional (2D) layer is vital in building novel functional vertical heterostructure. The monolayer 1T'-TMDCs has become one of the widely studied QSH insulator. In this review, we review the recent progress in fabrications of monolayer 1T'-TMDCs and evidence that establishes it as QSH insulator.
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Affiliation(s)
- Zhuojun Li
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, People's Republic of China
- CAS Center for Excellence in Superconducting Electronics (CENSE), Shanghai 200050, People's Republic of China
| | - Yekai Song
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, People's Republic of China
- CAS Center for Excellence in Superconducting Electronics (CENSE), Shanghai 200050, People's Republic of China
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 200031, People's Republic of China
| | - Shujie Tang
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, People's Republic of China
- CAS Center for Excellence in Superconducting Electronics (CENSE), Shanghai 200050, People's Republic of China
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44
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Zhao W, Fei Z, Song T, Choi HK, Palomaki T, Sun B, Malinowski P, McGuire MA, Chu JH, Xu X, Cobden DH. Magnetic proximity and nonreciprocal current switching in a monolayer WTe 2 helical edge. NATURE MATERIALS 2020; 19:503-507. [PMID: 32152559 DOI: 10.1038/s41563-020-0620-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 01/21/2020] [Indexed: 06/10/2023]
Abstract
The integration of diverse electronic phenomena, such as magnetism and nontrivial topology, into a single system is normally studied either by seeking materials that contain both ingredients, or by layered growth of contrasting materials1-9. The ability to simply stack very different two-dimensional van der Waals materials in intimate contact permits a different approach10,11. Here we use this approach to couple the helical edges states in a two-dimensional topological insulator, monolayer WTe2 (refs. 12-16), to a two-dimensional layered antiferromagnet, CrI3 (ref. 17). We find that the edge conductance is sensitive to the magnetization state of the CrI3, and the coupling can be understood in terms of an exchange field from the nearest and next-nearest CrI3 layers that produces a gap in the helical edge. We also find that the nonlinear edge conductance depends on the magnetization of the nearest CrI3 layer relative to the current direction. At low temperatures this produces an extraordinarily large nonreciprocal current that is switched by changing the antiferromagnetic state of the CrI3.
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Affiliation(s)
- Wenjin Zhao
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Zaiyao Fei
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Tiancheng Song
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Han Kyou Choi
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Tauno Palomaki
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Bosong Sun
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Paul Malinowski
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Michael A McGuire
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Jiun-Haw Chu
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, USA.
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA.
| | - David H Cobden
- Department of Physics, University of Washington, Seattle, WA, USA.
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45
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Cucchi I, Gutiérrez-Lezama I, Cappelli E, McKeown Walker S, Bruno FY, Tenasini G, Wang L, Ubrig N, Barreteau C, Giannini E, Gibertini M, Tamai A, Morpurgo AF, Baumberger F. Microfocus Laser-Angle-Resolved Photoemission on Encapsulated Mono-, Bi-, and Few-Layer 1T'-WTe 2. NANO LETTERS 2019; 19:554-560. [PMID: 30570259 DOI: 10.1021/acs.nanolett.8b04534] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Two-dimensional crystals of semi-metallic van der Waals materials hold much potential for the realization of novel phases, as exemplified by the recent discoveries of a polar metal in few-layer 1T'-WTe2 and of a quantum spin Hall state in monolayers of the same material. Understanding these phases is particularly challenging because little is known from experiments about the momentum space electronic structure of ultrathin crystals. Here, we report direct electronic structure measurements of exfoliated mono-, bi-, and few-layer 1T'-WTe2 by laser-based microfocus angle-resolved photoemission. This is achieved by encapsulating with monolayer graphene a flake of WTe2 comprising regions of different thickness. Our data support the recent identification of a quantum spin Hall state in monolayer 1T'-WTe2 and reveal strong signatures of the broken inversion symmetry in the bilayer. We finally discuss the sensitivity of encapsulated samples to contaminants following exposure to ambient atmosphere.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - Marco Gibertini
- National Centre for Computational Design and Discovery of Novel Materials (MARVEL) , École Polytechnique Fedérale de Lausanne , CH-1015 Lausanne , Switzerland
| | | | | | - Felix Baumberger
- Swiss Light Source , Paul Scherrer Institute , CH-5232 Villigen , Switzerland
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