1
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Romero MR, Bracamonte AG. Optical Active Meta-Surfaces, -Substrates, and Single Quantum Dots Based on Tuning Organic Composites with Graphene. MATERIALS (BASEL, SWITZERLAND) 2024; 17:3242. [PMID: 38998324 PMCID: PMC11242519 DOI: 10.3390/ma17133242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2024] [Revised: 06/24/2024] [Accepted: 06/28/2024] [Indexed: 07/14/2024]
Abstract
In this communication, the design and fabrication of optical active metamaterials were developed by the incorporation of graphene and joining it to different substrates with variable spectroscopical properties. It focuses on how graphene and its derivatives could generate varied optical setups and materials considering modified and enhanced optics within substrates and surfaces. In this manner, it is discussed how light could be tuned and modified along its path from confined nano-patterned surfaces or through a modified micro-lens. In addition to these optical properties generated from the physical interaction of light, it should be added that the non-classical light pathways and quantum phenomena could participate. In this way, graphene and related carbon-based materials with particular properties, such as highly condensed electronics, pseudo-electromagnetic properties, and quantum and luminescent properties, could be incorporated. Therefore, the modified substrates could be switched by photo-stimulation with variable responses depending on the nature of the material constitution. Therefore, the optical properties of graphene and its derivatives are discussed in these types of metasurfaces with targeted optical active properties, such as within the UV, IR, and terahertz wavelength intervals, along with their further properties and respective potential applications.
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Affiliation(s)
- Marcelo R. Romero
- Departamento de Química Orgánica, Facultad de Ciencias Químicas (Universidad Nacional de Córdoba), IPQA−CONICET, Córdoba CP 5000, Argentina;
| | - A. Guillermo Bracamonte
- Departamento de Química Orgánica, Facultad de Ciencias Químicas, Instituto de Investigaciones en Físicoquímica de Córdoba (INFIQC), Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba CP 5000, Argentina
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2
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Yu X, Peng Z, Xu L, Shi W, Li Z, Meng X, He X, Wang Z, Duan S, Tong L, Huang X, Miao X, Hu W, Ye L. Manipulating 2D Materials through Strain Engineering. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2402561. [PMID: 38818684 DOI: 10.1002/smll.202402561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2024] [Revised: 05/15/2024] [Indexed: 06/01/2024]
Abstract
This review explores the growing interest in 2D layered materials, such as graphene, h-BN, transition metal dichalcogenides (TMDs), and black phosphorus (BP), with a specific focus on recent advances in strain engineering. Both experimental and theoretical results are delved into, highlighting the potential of strain to modulate physical properties, thereby enhancing device performance. Various strain engineering methods are summarized, and the impact of strain on the electrical, optical, magnetic, thermal, and valleytronic properties of 2D materials is thoroughly examined. Finally, the review concludes by addressing potential applications and challenges in utilizing strain engineering for functional devices, offering valuable insights for further research and applications in optoelectronics, thermionics, and spintronics.
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Affiliation(s)
- Xiangxiang Yu
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
- School of Physic and Optoelectronic Engineering, Yangtze University, Jingzhou, Hubei, 434023, China
| | - Zhuiri Peng
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Langlang Xu
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Wenhao Shi
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Zheng Li
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Xiaohan Meng
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Xiao He
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Zhen Wang
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, China
| | - Shikun Duan
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, China
| | - Lei Tong
- Department of Electronic Engineering, Materials Science and Technology Research Center, The Chinese University of Hong Kong, Hong Kong, 999077, China
| | - Xinyu Huang
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Xiangshui Miao
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
- Hubei Yangtze Memory Laboratories, Wuhan, 430205, China
| | - Weida Hu
- State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, China
| | - Lei Ye
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
- Hubei Yangtze Memory Laboratories, Wuhan, 430205, China
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3
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McRae AC, Wei G, Huang L, Yigen S, Tayari V, Champagne AR. Mechanical Control of Quantum Transport in Graphene. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024:e2313629. [PMID: 38558481 DOI: 10.1002/adma.202313629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 03/16/2024] [Indexed: 04/04/2024]
Abstract
2D materials (2DMs) are fundamentally electro-mechanical systems. Their environment unavoidably strains them and modifies their quantum transport properties. For instance, a simple uniaxial strain can completely turn off the conductance of ballistic graphene or switch on/off the superconducting phase of magic-angle bilayer graphene. This article reports measurements of quantum transport in strained graphene transistors which agree quantitatively with models based on mechanically-induced gauge potentials. A scalar potential is mechanically induced in situ to modify graphene's work function by up to 25 meV. Mechanically generated vector potentials suppress the ballistic conductance of graphene by up to 30% and control its quantum interferences. The data are measured with a custom experimental platform able to precisely tune both the mechanics and electrostatics of suspended graphene transistors at low-temperature over a broad range of strain (up to 2.6%). This work opens many opportunities to harness quantitative strain effects in 2DM quantum transport and technologies.
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Affiliation(s)
- Andrew C McRae
- Department of Physics, Concordia University, Montréal, Québec, H4B 1R6, Canada
| | - Guoqing Wei
- Department of Physics, Concordia University, Montréal, Québec, H4B 1R6, Canada
| | - Linxiang Huang
- Department of Physics, Concordia University, Montréal, Québec, H4B 1R6, Canada
| | - Serap Yigen
- Department of Physics, Concordia University, Montréal, Québec, H4B 1R6, Canada
| | - Vahid Tayari
- Department of Physics, Concordia University, Montréal, Québec, H4B 1R6, Canada
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4
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Lin F, Cao Z, Xiao F, Liu J, Qiao J, Xue M, Hu Z, Liu Y, Lu H, Zhang Z, Martin J, Tong Q, Guo W, Liu Y. Graphene binding on black phosphorus enables high on/off ratios and mobility. Natl Sci Rev 2024; 11:nwad279. [PMID: 38213527 PMCID: PMC10776355 DOI: 10.1093/nsr/nwad279] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 10/07/2023] [Accepted: 10/27/2023] [Indexed: 01/13/2024] Open
Abstract
Graphene is one of the most promising candidates for integrated circuits due to its robustness against short-channel effects, inherent high carrier mobility and desired gapless nature for Ohmic contact, but it is difficult to achieve satisfactory on/off ratios even at the expense of its carrier mobility, limiting its device applications. Here, we present a strategy to realize high back-gate switching ratios in a graphene monolayer with well-maintained high mobility by forming a vertical heterostructure with a black phosphorus multi-layer. By local current annealing, strain is introduced within an established area of the graphene, which forms a reflective interface with the rest of the strain-free area and thus generates a robust off-state via local current depletion. Applying a positive back-gate voltage to the heterostructure can keep the black phosphorus insulating, while a negative back-gate voltage changes the black phosphorus to be conductive because of hole accumulation. Then, a parallel channel is activated within the strain-free graphene area by edge-contacted electrodes, thereby largely inheriting the intrinsic carrier mobility of graphene in the on-state. As a result, the device can provide an on/off voltage ratio of >103 as well as a mobility of ∼8000 cm2 V-1 s-1 at room temperature, meeting the low-power criterion suggested by the International Roadmap for Devices and Systems.
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Affiliation(s)
- Fanrong Lin
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing210016, China
| | - Zhonghan Cao
- Centre for Advanced 2D Materials, National University of Singapore, Singapore 117546, Singapore
| | - Feiping Xiao
- School of Physics and Electronics, Hunan University, Changsha410082, China
| | - Jiawei Liu
- Centre for Advanced 2D Materials, National University of Singapore, Singapore 117546, Singapore
| | - Jiabin Qiao
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement, School of Physics, Beijing Institute of Technology, Beijing100081, China
| | - Minmin Xue
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing210016, China
| | - Zhili Hu
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing210016, China
| | - Ying Liu
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing210016, China
| | - Huan Lu
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing210016, China
| | - Zhuhua Zhang
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing210016, China
| | - Jens Martin
- Leibniz Institute für Kristallzüchtung, Berlin12489, Germany
| | - Qingjun Tong
- School of Physics and Electronics, Hunan University, Changsha410082, China
| | - Wanlin Guo
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing210016, China
| | - Yanpeng Liu
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing210016, China
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5
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Zhou H, Auerbach N, Uzan M, Zhou Y, Banu N, Zhi W, Huber ME, Watanabe K, Taniguchi T, Myasoedov Y, Yan B, Zeldov E. Imaging quantum oscillations and millitesla pseudomagnetic fields in graphene. Nature 2023; 624:275-281. [PMID: 37993718 PMCID: PMC10719110 DOI: 10.1038/s41586-023-06763-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Accepted: 10/19/2023] [Indexed: 11/24/2023]
Abstract
The exceptional control of the electronic energy bands in atomically thin quantum materials has led to the discovery of several emergent phenomena1. However, at present there is no versatile method for mapping the local band structure in advanced two-dimensional materials devices in which the active layer is commonly embedded in the insulating layers and metallic gates. Using a scanning superconducting quantum interference device, here we image the de Haas-van Alphen quantum oscillations in a model system, the Bernal-stacked trilayer graphene with dual gates, which shows several highly tunable bands2-4. By resolving thermodynamic quantum oscillations spanning more than 100 Landau levels in low magnetic fields, we reconstruct the band structure and its evolution with the displacement field with excellent precision and nanoscale spatial resolution. Moreover, by developing Landau-level interferometry, we show shear-strain-induced pseudomagnetic fields and map their spatial dependence. In contrast to artificially induced large strain, which leads to pseudomagnetic fields of hundreds of tesla5-7, we detect naturally occurring pseudomagnetic fields as low as 1 mT corresponding to graphene twisting by 1 millidegree, two orders of magnitude lower than the typical angle disorder in twisted bilayer graphene8-11. This ability to resolve the local band structure and strain at the nanoscale level enables the characterization and use of tunable band engineering in practical van der Waals devices.
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Affiliation(s)
- Haibiao Zhou
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Nadav Auerbach
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Matan Uzan
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Yaozhang Zhou
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Nasrin Banu
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Weifeng Zhi
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Martin E Huber
- Departments of Physics and Electrical Engineering, University of Colorado Denver, Denver, CO, USA
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Yuri Myasoedov
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Binghai Yan
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Eli Zeldov
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel.
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6
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Naumis GG, Herrera SA, Poudel SP, Nakamura H, Barraza-Lopez S. Mechanical, electronic, optical, piezoelectric and ferroic properties of strained graphene and other strained monolayers and multilayers: an update. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2023; 87:016502. [PMID: 37879327 DOI: 10.1088/1361-6633/ad06db] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 10/25/2023] [Indexed: 10/27/2023]
Abstract
This is an update of a previous review (Naumiset al2017Rep. Prog. Phys.80096501). Experimental and theoretical advances for straining graphene and other metallic, insulating, ferroelectric, ferroelastic, ferromagnetic and multiferroic 2D materials were considered. We surveyed (i) methods to induce valley and sublattice polarisation (P) in graphene, (ii) time-dependent strain and its impact on graphene's electronic properties, (iii) the role of local and global strain on superconductivity and other highly correlated and/or topological phases of graphene, (iv) inducing polarisationPon hexagonal boron nitride monolayers via strain, (v) modifying the optoelectronic properties of transition metal dichalcogenide monolayers through strain, (vi) ferroic 2D materials with intrinsic elastic (σ), electric (P) and magnetic (M) polarisation under strain, as well as incipient 2D multiferroics and (vii) moiré bilayers exhibiting flat electronic bands and exotic quantum phase diagrams, and other bilayer or few-layer systems exhibiting ferroic orders tunable by rotations and shear strain. The update features the experimental realisations of a tunable two-dimensional Quantum Spin Hall effect in germanene, of elemental 2D ferroelectric bismuth, and 2D multiferroic NiI2. The document was structured for a discussion of effects taking place in monolayers first, followed by discussions concerning bilayers and few-layers, and it represents an up-to-date overview of exciting and newest developments on the fast-paced field of 2D materials.
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Affiliation(s)
- Gerardo G Naumis
- Departamento de Sistemas Complejos, Instituto de Física, Universidad Nacional Autónoma de México (UNAM), Apdo. Postal 20-364, CDMX, 01000, Mexico
| | - Saúl A Herrera
- Departamento de Sistemas Complejos, Instituto de Física, Universidad Nacional Autónoma de México (UNAM), Apdo. Postal 20-364, CDMX, 01000, Mexico
| | - Shiva P Poudel
- Department of Physics, University of Arkansas, Fayetteville, AR 72701, United States of America
- MonArk NSF Quantum Foundry, University of Arkansas, Fayetteville, AR 72701, United States of America
| | - Hiro Nakamura
- Department of Physics, University of Arkansas, Fayetteville, AR 72701, United States of America
- MonArk NSF Quantum Foundry, University of Arkansas, Fayetteville, AR 72701, United States of America
| | - Salvador Barraza-Lopez
- Department of Physics, University of Arkansas, Fayetteville, AR 72701, United States of America
- MonArk NSF Quantum Foundry, University of Arkansas, Fayetteville, AR 72701, United States of America
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7
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Sharma S, Gill D, Shallcross S. Giant and Controllable Valley Currents in Graphene by Double Pumped THz Light. NANO LETTERS 2023; 23:10305-10310. [PMID: 37956341 DOI: 10.1021/acs.nanolett.3c02874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
The field of valleytronics considers the creation and manipulation of "valley states", charge excitations characterized by a particular value of the crystal momentum in the Brillouin zone. Here we show, using the example of minimally gapped (≤40 meV) graphene, that there exist lightforms that create almost perfect valley contrasting current states (up to ∼80% valley purity) in the absence of a valley contrasting charge excitation. These "momentum streaked" THz waveforms act by deforming the excited state population in momentum space such that current flows at one valley yet is blocked at the conjugate valley. This approach both unlocks the potential of graphene as a materials platform for valleytronics, as gaps of 10-40 meV are robustly found in useful experimental contexts such as graphene/hBN systems, while simultaneously providing a tool toward ultrafast light control of valley currents in diverse minimally gapped matter, including many topological insulator systems.
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Affiliation(s)
- Sangeeta Sharma
- Max-Born-Institute for Non-linear Optics and Short Pulse Spectroscopy, Max-Born Strasse 2A, 12489 Berlin, Germany
- Institute for Theoretical Solid-State Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Deepika Gill
- Max-Born-Institute for Non-linear Optics and Short Pulse Spectroscopy, Max-Born Strasse 2A, 12489 Berlin, Germany
| | - Samuel Shallcross
- Max-Born-Institute for Non-linear Optics and Short Pulse Spectroscopy, Max-Born Strasse 2A, 12489 Berlin, Germany
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8
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Zhang H, Weinert M, Li L. Giant Periodic Pseudomagnetic Fields in Strained Kagome Magnet FeSn Epitaxial Films on SrTiO 3(111) Substrate. NANO LETTERS 2023; 23:2397-2404. [PMID: 36912449 PMCID: PMC10037333 DOI: 10.1021/acs.nanolett.3c00345] [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: 02/09/2023] [Revised: 03/08/2023] [Indexed: 06/18/2023]
Abstract
Quantum materials, particularly Dirac materials with linearly dispersing bands, can be effectively tuned by strain-induced lattice distortions leading to a pseudomagnetic field that strongly modulates their electronic properties. Here, we grow kagome magnet FeSn films, consisting of alternatingly stacked Sn2 honeycomb (stanene) and Fe3Sn kagome layers, on SrTiO3(111) substrates by molecular beam epitaxy. Using scanning tunneling microscopy/spectroscopy, we show that the Sn honeycomb layer can be periodically deformed by epitaxial strain for a film thickness below 10 nm, resulting in differential conductance peaks consistent with Landau levels generated by a pseudomagnetic field greater than 1000 T. Our findings demonstrate the feasibility of strain engineering the electronic properties of topological magnets at the nanoscale.
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Affiliation(s)
- Huimin Zhang
- Department
of Physics and Astronomy, West Virginia
University, Morgantown, West Virginia 26506, United States
- State
Key Laboratory of Structural Analysis, Optimization and CAE Software
for Industrial Equipment, Dalian University
of Technology, Dalian, 116024, China
| | - Michael Weinert
- Department
of Physics, University of Wisconsin, Milwaukee, Wisconsin 53201, United States
| | - Lian Li
- Department
of Physics and Astronomy, West Virginia
University, Morgantown, West Virginia 26506, United States
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9
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Zanotto S, Bonatti L, Pantano MF, Mišeikis V, Speranza G, Giovannini T, Coletti C, Cappelli C, Tredicucci A, Toncelli A. Strain-Induced Plasmon Confinement in Polycrystalline Graphene. ACS PHOTONICS 2023; 10:394-400. [PMID: 36820323 PMCID: PMC9936574 DOI: 10.1021/acsphotonics.2c01157] [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: 07/24/2022] [Indexed: 06/18/2023]
Abstract
Terahertz spectroscopy is a perfect tool to investigate the electronic intraband conductivity of graphene, but a phenomenological model (Drude-Smith) is often needed to describe disorder. By studying the THz response of isotropically strained polycrystalline graphene and using a fully atomistic computational approach to fit the results, we demonstrate here the connection between the Drude-Smith parameters and the microscopic behavior. Importantly, we clearly show that the strain-induced changes in the conductivity originate mainly from the increased separation between the single-crystal grains, leading to enchanced localization of the plasmon excitations. Only at the lowest strain values explored, a behavior consistent with the deformation of the individual grains can instead be observed.
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Affiliation(s)
- Simone Zanotto
- NEST, Istituto Nanoscienze − CNR and Scuola Normale
Superiore, Piazza S. Silvestro 12, Pisa, 56127, Italy
| | - Luca Bonatti
- Scuola
Normale Superiore, Piazza dei Cavalieri 7, Pisa, 56126, Italy
| | - Maria F. Pantano
- Department
of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, Trento, 38123, Italy
| | - Vaidotas Mišeikis
- Center
for Nanotechnology Innovation @NEST - Istituto Italiano di Tecnologia, Piazza S. Silvestro 12, Pisa, 56127, Italy
| | - Giorgio Speranza
- Centre
for Materials and Microsystems, Fondazione
Bruno Kessler, via Sommarive 18, Trento, I-38123, Italy
| | | | - Camilla Coletti
- Center
for Nanotechnology Innovation @NEST - Istituto Italiano di Tecnologia, Piazza S. Silvestro 12, Pisa, 56127, Italy
| | - Chiara Cappelli
- Scuola
Normale Superiore, Piazza dei Cavalieri 7, Pisa, 56126, Italy
| | - Alessandro Tredicucci
- Dipartimento
di Fisica ”E. Fermi” and CISUP, Università di Pisa, and Istituto Nanoscienze - CNR, Largo Pontecorvo 3, Pisa, 56127, Italy
| | - Alessandra Toncelli
- Dipartimento
di Fisica ”E. Fermi” and CISUP, Università di Pisa, and Istituto Nanoscienze - CNR, Largo Pontecorvo 3, Pisa, 56127, Italy
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10
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Liu YW, Zhan Z, Wu Z, Yan C, Yuan S, He L. Realizing One-Dimensional Electronic States in Graphene via Coupled Zeroth Pseudo-Landau Levels. PHYSICAL REVIEW LETTERS 2022; 129:056803. [PMID: 35960565 DOI: 10.1103/physrevlett.129.056803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 06/17/2022] [Accepted: 07/06/2022] [Indexed: 06/15/2023]
Abstract
Strain-induced pseudomagnetic fields can mimic real magnetic fields to generate a zero-magnetic-field analog of the Landau levels (LLs), i.e., the pseudo-Landau levels (PLLs), in graphene. The distinct nature of the PLLs enables one to realize novel electronic states beyond what is feasible with real LLs. Here, we show that it is possible to realize exotic electronic states through the coupling of zeroth PLLs in strained graphene. In our experiment, nanoscale strained structures embedded with PLLs are generated along a one-dimensional (1D) channel of suspended graphene monolayer. Our results demonstrate that the zeroth PLLs of the strained structures are coupled together, exhibiting a serpentine pattern that snakes back and forth along the 1D suspended graphene monolayer. These results are verified theoretically by large-scale tight-binding calculations of the strained samples. Our result provides a new approach to realizing novel quantum states and to engineering the electronic properties of graphene by using localized PLLs as building blocks.
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Affiliation(s)
- Yi-Wen Liu
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing, 100875, People's Republic of China
| | - Zhen Zhan
- Key Laboratory of Artificial Micro- and Nano-structures of the Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Zewen Wu
- Key Laboratory of Artificial Micro- and Nano-structures of the Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Chao Yan
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing, 100875, People's Republic of China
| | - Shengjun Yuan
- Key Laboratory of Artificial Micro- and Nano-structures of the Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072, China
- Wuhan Institute of Quantum Technology, Wuhan 340206, China
| | - Lin He
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing, 100875, People's Republic of China
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11
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Qu AC, Nigge P, Link S, Levy G, Michiardi M, Spandar PL, Matthé T, Schneider M, Zhdanovich S, Starke U, Gutiérrez C, Damascelli A. Ubiquitous defect-induced density wave instability in monolayer graphene. SCIENCE ADVANCES 2022; 8:eabm5180. [PMID: 35675409 PMCID: PMC9177069 DOI: 10.1126/sciadv.abm5180] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 04/20/2022] [Indexed: 06/15/2023]
Abstract
Quantum materials are notoriously sensitive to their environments, where small perturbations can tip a system toward one of several competing ground states. Graphene hosts a rich assortment of such competing phases, including a bond density wave instability ("Kekulé distortion") that couples electrons at the K/K' valleys and breaks the lattice symmetry. Here, we report observations of a ubiquitous Kekulé distortion across multiple graphene systems. We show that extremely dilute concentrations of surface atoms (less than three adsorbed atoms every 1000 graphene unit cells) can self-assemble and trigger the onset of a global Kekulé density wave phase. Combining complementary momentum-sensitive angle-resolved photoemission spectroscopy (ARPES) and low-energy electron diffraction (LEED) measurements, we confirm the presence of this density wave phase and observe the opening of an energy gap. Our results reveal an unexpected sensitivity of the graphene lattice to dilute surface disorder and show that adsorbed atoms offer an attractive route toward designing novel phases in two-dimensional materials.
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Affiliation(s)
- A. C. Qu
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, Canada
| | - P. Nigge
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, Canada
| | - S. Link
- Max Planck Institute for Solid State Research, Stuttgart, Germany
| | - G. Levy
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, Canada
| | - M. Michiardi
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, Canada
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
| | - P. L. Spandar
- Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, CA, USA
| | - T. Matthé
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, Canada
| | - M. Schneider
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, Canada
| | - S. Zhdanovich
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, Canada
| | - U. Starke
- Max Planck Institute for Solid State Research, Stuttgart, Germany
| | - C. Gutiérrez
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, Canada
- Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, CA, USA
| | - A. Damascelli
- Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, Canada
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12
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Berman OL, Kezerashvili RY, Lozovik YE, Ziegler KG. Strain-induced quantum Hall phenomena of excitons in graphene. Sci Rep 2022; 12:2950. [PMID: 35194045 PMCID: PMC8863812 DOI: 10.1038/s41598-022-06486-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 01/24/2022] [Indexed: 11/28/2022] Open
Abstract
We study direct and indirect pseudomagnetoexcitons, formed by an electron and a hole in the layers of gapped graphene under strain-induced gauge pseudomagnetic field. Since the strain-induced pseudomagnetic field acts on electrons and holes the same way, it occurs that the properties of single pseudomagnetoexcitons, their collective effects and phase diagram are cardinally different from those of magnetoexcitons in a real magnetic field. We have derived wave functions and energy spectrum of direct in a monolayer and indirect pseudomagnetoexcitons in a double layer of gapped graphene. The quantum Hall effect for direct and indirect excitons was predicted in the monolayers and double layers of gapped graphene under strain-induced gauge pseudomagnetic field, correspondingly.
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Affiliation(s)
- Oleg L Berman
- Physics Department, New York City College of Technology, The City University of New York, Brooklyn, NY, 11201, USA.,The Graduate School and University Center, The City University of New York, New York, NY, 10016, USA
| | - Roman Ya Kezerashvili
- Physics Department, New York City College of Technology, The City University of New York, Brooklyn, NY, 11201, USA. .,The Graduate School and University Center, The City University of New York, New York, NY, 10016, USA.
| | - Yurii E Lozovik
- Institute of Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow, Russia, 142190.,Research University Higher School of Economics, Moscow, Russia, 101000
| | - Klaus G Ziegler
- Institut für Physik, Universität Augsburg, 86135, Augsburg, Germany
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13
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Lu M, Zhang XX, Franz M. Magnetic Suppression of Non-Hermitian Skin Effects. PHYSICAL REVIEW LETTERS 2021; 127:256402. [PMID: 35029425 DOI: 10.1103/physrevlett.127.256402] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 10/27/2021] [Indexed: 06/14/2023]
Abstract
Skin effect, where macroscopically many bulk states are aggregated toward the system boundary, is one of the most important and distinguishing phenomena in non-Hermitian quantum systems. We discuss a new aspect of this effect whereby, despite its topological origin, applying a magnetic field can largely suppress it. Skin states are pushed back into the bulk, and the skin topological area, which we define, is sharply reduced. As seen from exact solutions of representative models, this is fundamentally rooted in the fact that the applied magnetic field restores the validity of the low-energy description that is rendered inapplicable in the presence of non-Bloch skin states. We further study this phenomenon using rational gauge fluxes, which reveals a unique irrelevance of the generalized Brillouin zone in the standard non-Bloch band theory of non-Hermitian systems.
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Affiliation(s)
- Ming Lu
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Xiao-Xiao Zhang
- Department of Physics and Astronomy and Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - Marcel Franz
- Department of Physics and Astronomy and Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
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14
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Yan M, Deng W, Huang X, Wu Y, Yang Y, Lu J, Li F, Liu Z. Pseudomagnetic Fields Enabled Manipulation of On-Chip Elastic Waves. PHYSICAL REVIEW LETTERS 2021; 127:136401. [PMID: 34623863 DOI: 10.1103/physrevlett.127.136401] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 08/27/2021] [Indexed: 06/13/2023]
Abstract
The physical realization of pseudomagnetic fields (PMFs) is an engaging frontier of research. As in graphene, elastic PMF can be realized by the structural modulations of Dirac materials. We show that, in the presence of PMFs, the conical dispersions split into elastic Landau levels, and the elastic modes robustly propagate along the edges, similar to the quantum Hall edge transports. In particular, we reveal unique elastic snake states in an on-chip heterostructure with two opposite PMFs. The flexibility in the micromanufacture of silicon chips and the low loss of elastic waves provide an unprecedented opportunity to demonstrate various fascinating topological transports of the edge states under PMFs. These properties open new possibilities for designing functional elastic wave devices in miniature and compact scales.
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Affiliation(s)
- Mou Yan
- School of Physics and Optoelectronics, South China University of Technology, Guangzhou, Guangdong 510640, China
| | - Weiyin Deng
- School of Physics and Optoelectronics, South China University of Technology, Guangzhou, Guangdong 510640, China
| | - Xueqin Huang
- School of Physics and Optoelectronics, South China University of Technology, Guangzhou, Guangdong 510640, China
| | - Ying Wu
- School of Physics and Optoelectronics, South China University of Technology, Guangzhou, Guangdong 510640, China
| | - Yating Yang
- School of Physics and Optoelectronics, South China University of Technology, Guangzhou, Guangdong 510640, China
| | - Jiuyang Lu
- School of Physics and Optoelectronics, South China University of Technology, Guangzhou, Guangdong 510640, China
| | - Feng Li
- School of Physics and Optoelectronics, South China University of Technology, Guangzhou, Guangdong 510640, China
| | - Zhengyou Liu
- Key Laboratory of Artificial Micro- and Nanostructures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072, China
- Institute for Advanced Studies, Wuhan University, Wuhan 430072, China
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15
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Liang L, Sukhachov PO, Balatsky AV. Axial Magnetoelectric Effect in Dirac Semimetals. PHYSICAL REVIEW LETTERS 2021; 126:247202. [PMID: 34213932 DOI: 10.1103/physrevlett.126.247202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Revised: 03/01/2021] [Accepted: 05/18/2021] [Indexed: 06/13/2023]
Abstract
We propose a mechanism to generate a static magnetization via the "axial magnetoelectric effect" (AMEE). Magnetization M∼E_{5}(ω)×E_{5}^{*}(ω) appears as a result of the transfer of the angular momentum of the axial electric field E_{5}(t) into the magnetic moment in Dirac and Weyl semimetals. We point out similarities and differences between the proposed AMEE and a conventional inverse Faraday effect. As an example, we estimated the AMEE generated by circularly polarized acoustic waves and find it to be on the scale of microgauss for gigahertz frequency sound. In contrast to a conventional inverse Faraday effect, magnetization rises linearly at small frequencies and fixed sound intensity as well as demonstrates a nonmonotonic peak behavior for the AMEE. The effect provides a way to investigate unusual axial electromagnetic fields via conventional magnetometry techniques.
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Affiliation(s)
- Long Liang
- Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-106 91 Stockholm, Sweden
| | - P O Sukhachov
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
| | - A V Balatsky
- Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-106 91 Stockholm, Sweden
- Department of Physics and Institute for Materials Science, University of Connecticut, Storrs, Connecticut 06269, USA
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16
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Zhai D, Yao W. Layer Pseudospin Dynamics and Genuine Non-Abelian Berry Phase in Inhomogeneously Strained Moiré Pattern. PHYSICAL REVIEW LETTERS 2020; 125:266404. [PMID: 33449753 DOI: 10.1103/physrevlett.125.266404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 12/08/2020] [Indexed: 06/12/2023]
Abstract
Periodicity of long wavelength moiré patterns is very often destroyed by the inhomogeneous strain introduced in fabrications of van der Waals layered structures. We present a framework to describe massive Dirac fermions in such distorted moiré pattern of transition metal dichalcogenides homobilayers, accounting for the dynamics of layer pseudospin. In decoupled bilayers, we show two causes of in-plane layer pseudospin precession: By the coupling of layer antisymmetric strain to valley magnetic moment; and by the Aharonov-Bohm effect in the SU(2) gauge potential for the case of R-type bilayer under antisymmetric strain and H-type under symmetric strain. With interlayer coupling in the moiré, its interplay with strain manifests as a non-Abelian gauge field. We show a genuine non-Abelian Aharonov-Bohm effect in such field, where the evolution operators for different loops are noncommutative. This provides an exciting platform to explore non-Abelian gauge field effects on electron, with remarkable tunability of the field by strain and interlayer bias.
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Affiliation(s)
- Dawei Zhai
- Department of Physics, The University of Hong Kong, and HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong, China
| | - Wang Yao
- Department of Physics, The University of Hong Kong, and HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong, China
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17
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Andrei EY, MacDonald AH. Graphene bilayers with a twist. NATURE MATERIALS 2020; 19:1265-1275. [PMID: 33208935 DOI: 10.1038/s41563-020-00840-0] [Citation(s) in RCA: 164] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 09/24/2020] [Indexed: 05/02/2023]
Abstract
Near a magic twist angle, bilayer graphene transforms from a weakly correlated Fermi liquid to a strongly correlated two-dimensional electron system with properties that are extraordinarily sensitive to carrier density and to controllable environmental factors such as the proximity of nearby gates and twist-angle variation. Among other phenomena, magic-angle twisted bilayer graphene hosts superconductivity, interaction-induced insulating states, magnetism, electronic nematicity, linear-in-temperature low-temperature resistivity and quantized anomalous Hall states. We highlight some key research results in this field, point to important questions that remain open and comment on the place of magic-angle twisted bilayer graphene in the strongly correlated quantum matter world.
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Affiliation(s)
- Eva Y Andrei
- Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
| | - Allan H MacDonald
- Department of Physics, The University of Texas at Austin, Austin, TX, USA
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18
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Wang W, Gao W, Chen X, Shi F, Li G, Dong J, Xiang Y, Zhang S. Moiré Fringe Induced Gauge Field in Photonics. PHYSICAL REVIEW LETTERS 2020; 125:203901. [PMID: 33258635 DOI: 10.1103/physrevlett.125.203901] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Accepted: 10/23/2020] [Indexed: 06/12/2023]
Abstract
We realize moiré fringe induced gauge field in a double-layer photonic honeycomb metacrystal with mismatched lattice constants. Benefitting from the generated strong effective gauge field, we report direct measurement of the band diagrams of both Landau level flat bands and intermagnetic-domain edge states. Importantly, we observe the correlation between the momentum and orbital position of the Landau modes, serving as an evidence of the noncommuteness between orthogonal components of the momentum. Without complicated time driving mechanics and careful site-by-site engineering, moiré superlattices could emerge as a powerful means to generate effective gauge fields for photonics benefiting from its simplicity and reconfigurability, which can be applied to nonlinearity enhancement and lasing applications at optical frequencies.
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Affiliation(s)
- Wenhui Wang
- School of Physics & Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Wenlong Gao
- School of Physics & Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Xiaodong Chen
- School of Physics & State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, China
| | - Fulong Shi
- School of Physics & State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, China
| | - Guixin Li
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Jianwen Dong
- School of Physics & State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, China
| | - Yuanjiang Xiang
- School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Shuang Zhang
- School of Physics & Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
- Department of Physics, University of Hong Kong, Hong Kong, China
- Department of Electrical & Electronic Engineering, University of Hong Kong, Hong Kong, China
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19
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Ben Gouider Trabelsi A, V. Kusmartsev F, Kusmartseva A, H. Alkallas F, AlFaify S, Shkir M. Raman Spectroscopy Imaging of Exceptional Electronic Properties in Epitaxial Graphene Grown on SiC. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E2234. [PMID: 33187068 PMCID: PMC7696917 DOI: 10.3390/nano10112234] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 11/02/2020] [Accepted: 11/04/2020] [Indexed: 11/17/2022]
Abstract
Graphene distinctive electronic and optical properties have sparked intense interest throughout the scientific community bringing innovation and progress to many sectors of academia and industry. Graphene manufacturing has rapidly evolved since its discovery in 2004. The diverse growth methods of graphene have many comparative advantages in terms of size, shape, quality and cost. Specifically, epitaxial graphene is thermally grown on a silicon carbide (SiC) substrate. This type of graphene is unique due to its coexistence with the SiC underneath which makes the process of transferring graphene layers for devices manufacturing simple and robust. Raman analysis is a sensitive technique extensively used to explore nanocarbon material properties. Indeed, this method has been widely used in graphene studies in fundamental research and application fields. We review the principal Raman scattering processes in SiC substrate and demonstrate epitaxial graphene growth. We have identified the Raman bands signature of graphene for different layers number. The method could be readily adopted to characterize structural and exceptional electrical properties for various epitaxial graphene systems. Particularly, the variation of the charge carrier concentration in epitaxial graphene of different shapes and layers number have been precisely imaged. By comparing the intensity ratio of 2D line and G line-"I2D/IG"-the density of charge across the graphene layers could be monitored. The obtained results were compared to previous electrical measurements. The substrate longitudinal optical phonon coupling "LOOPC" modes have also been examined for several epitaxial graphene layers. The LOOPC of the SiC substrate shows a precise map of the density of charge in epitaxial graphene systems for different graphene layers number. Correlations between the density of charge and particular graphene layer shape such as bubbles have been determined. All experimental probes show a high degree of consistency and efficiency. Our combined studies have revealed novel capacitor effect in diverse epitaxial graphene system. The SiC substrate self-compensates the graphene layer charge without any external doping. We have observed a new density of charge at the graphene-substrate interface. The located capacitor effects at epitaxial graphene-substrate interfaces give rise to an unexpected mini gap in graphene band structure.
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Affiliation(s)
- A. Ben Gouider Trabelsi
- Department of Physics, College of Science, Princess Nourah bint Abdulrahman University, Riyadh PO Box 84428, Saudi Arabia;
| | - F. V. Kusmartsev
- Department of Physics, Loughborough University, Loughborough LE11 3TU, UK; (F.V.K.); (A.K.)
- Micro/Nano Fabrication Laboratory, Microsystem & Terahertz Research Centre of CAEP, Chengdu, China
| | - A. Kusmartseva
- Department of Physics, Loughborough University, Loughborough LE11 3TU, UK; (F.V.K.); (A.K.)
| | - F. H. Alkallas
- Department of Physics, College of Science, Princess Nourah bint Abdulrahman University, Riyadh PO Box 84428, Saudi Arabia;
| | - S. AlFaify
- Department of Physics, Faculty of Sciences, King Khalid University, Abha PO Box 61421, Saudi Arabia; (S.A.); (M.S.)
| | - Mohd Shkir
- Department of Physics, Faculty of Sciences, King Khalid University, Abha PO Box 61421, Saudi Arabia; (S.A.); (M.S.)
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20
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Banerjee R, Nguyen VH, Granzier-Nakajima T, Pabbi L, Lherbier A, Binion AR, Charlier JC, Terrones M, Hudson EW. Strain Modulated Superlattices in Graphene. NANO LETTERS 2020; 20:3113-3121. [PMID: 32134680 DOI: 10.1021/acs.nanolett.9b05108] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Numerous theoretically proposed devices and novel phenomena have sought to take advantage of the intense pseudogauge fields that can arise in strained graphene. Many of these proposals, however, require fields to oscillate with a spatial frequency smaller than the magnetic length, while to date only the generation and effects of fields varying at a much larger length scale have been reported. Here, we describe the creation of short wavelength, periodic pseudogauge-fields using rippled graphene under extreme (>10%) strain and study of its effects on Dirac electrons. Combining scanning tunneling microscopy and atomistic calculations, we find that spatially oscillating strain generates a new quantization different from the familiar Landau quantization. Graphene ripples also cause large variations in carbon-carbon bond length, creating an effective electronic superlattice within a single graphene sheet. Our results thus also establish a novel approach of synthesizing effective 2D lateral heterostructures by periodically modulating lattice strain.
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Affiliation(s)
- Riju Banerjee
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Viet-Hung Nguyen
- Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, Chemin des étoiles 8, B-1348 Louvain-la-Neuve, Belgium
| | - Tomotaroh Granzier-Nakajima
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Lavish Pabbi
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Aurelien Lherbier
- Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, Chemin des étoiles 8, B-1348 Louvain-la-Neuve, Belgium
| | - Anna Ruth Binion
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Jean-Christophe Charlier
- Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, Chemin des étoiles 8, B-1348 Louvain-la-Neuve, Belgium
| | - Mauricio Terrones
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Eric William Hudson
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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21
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Zhang XX, Franz M. Non-Hermitian Exceptional Landau Quantization in Electric Circuits. PHYSICAL REVIEW LETTERS 2020; 124:046401. [PMID: 32058750 DOI: 10.1103/physrevlett.124.046401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2019] [Indexed: 06/10/2023]
Abstract
Alternating current RLC electric circuits form an accessible and highly tunable platform simulating Hermitian as well as non-Hermitian (NH) quantum systems. We propose here a circuit realization of NH Dirac and Weyl Hamiltonians subject to time-reversal invariant pseudomagnetic field, enabling the exploration of novel NH physics. We identify the low-energy physics with a generic real energy spectrum from the NH Landau quantization of exceptional points and rings, which can avoid the NH skin effect and provides a physical example of a quasiparticle moving in the complex plane. Realistic detection schemes are designed to probe the flat energy bands, sublattice polarization, edge states protected by a NH energy-reflection symmetry, and a characteristic nodeless probability distribution.
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Affiliation(s)
- Xiao-Xiao Zhang
- Department of Physics and Astronomy & Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia, V6T 1Z4 Canada
| | - Marcel Franz
- Department of Physics and Astronomy & Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia, V6T 1Z4 Canada
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22
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Sela E, Bloch Y, von Oppen F, Shalom MB. Quantum Hall Response to Time-Dependent Strain Gradients in Graphene. PHYSICAL REVIEW LETTERS 2020; 124:026602. [PMID: 32004059 DOI: 10.1103/physrevlett.124.026602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Indexed: 06/10/2023]
Abstract
Mechanical deformations of graphene induce a term in the Dirac Hamiltonian that is reminiscent of an electromagnetic vector potential. Strain gradients along particular lattice directions induce local pseudomagnetic fields and substantial energy gaps as indeed observed experimentally. Expanding this analogy, we propose to complement the pseudomagnetic field by a pseudoelectric field, generated by a time-dependent oscillating stress applied to a graphene ribbon. The joint Hall-like response to these crossed fields results in a strain-induced charge current along the ribbon. We analyze in detail a particular experimental implementation in the (pseudo)quantum Hall regime with weak intervalley scattering. This allows us to predict an (approximately) quantized Hall current that is unaffected by screening due to diffusion currents.
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Affiliation(s)
- Eran Sela
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, IL-69978 Tel Aviv, Israel
| | - Yakov Bloch
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, IL-69978 Tel Aviv, Israel
| | - Felix von Oppen
- Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Moshe Ben Shalom
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, IL-69978 Tel Aviv, Israel
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