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Hu J, Han Y, Chi X, Omar GJ, Al Ezzi MME, Gou J, Yu X, Andrivo R, Watanabe K, Taniguchi T, Wee ATS, Qiao Z, Ariando A. Tunable Spin-Polarized States in Graphene on a Ferrimagnetic Oxide Insulator. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2305763. [PMID: 37811809 DOI: 10.1002/adma.202305763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 10/01/2023] [Indexed: 10/10/2023]
Abstract
Spin-polarized two-dimensional (2D) materials with large and tunable spin-splitting energy promise the field of 2D spintronics. While graphene has been a canonical 2D material, its spin properties and tunability are limited. Here, this work demonstrates the emergence of robust spin-polarization in graphene with large and tunable spin-splitting energy of up to 132 meV at zero applied magnetic fields. The spin polarization is induced through a magnetic exchange interaction between graphene and the underlying ferrimagnetic oxide insulating layer, Tm3 Fe5 O12 , as confirmed by its X-ray magnetic circular dichroism (XMCD). The spin-splitting energies are directly measured and visualized by the shift in their Landau-fan diagram mapped by analyzing the measured Shubnikov-de-Haas (SdH) oscillations as a function of applied electric fields, showing consistent fit with the first-principles and machine learning calculations. Further, the observed spin-splitting energies can be tuned over a broad range between 98 and 166 meV by field cooling. The methods and results are applicable to other 2D (magnetic) materials and heterostructures, and offer great potential for developing next-generation spin logic and memory devices.
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Affiliation(s)
- Junxiong Hu
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, 117551, Singapore
| | - Yulei Han
- International Center for Quantum Design of Functional Materials, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
- Department of Physics, Fuzhou University, Fuzhou, Fujian, 350108, China
| | - Xiao Chi
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
- Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore, 117603, Singapore
| | - Ganesh Ji Omar
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
| | - Mohammed Mohammed Esmail Al Ezzi
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, 117551, Singapore
| | - Jian Gou
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
| | - Xiaojiang Yu
- Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore, 117603, Singapore
| | - Rusydi Andrivo
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki, 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki, 305-0044, Japan
| | - Andrew Thye Shen Wee
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
| | - Zhenhua Qiao
- International Center for Quantum Design of Functional Materials, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei, 230088, China
| | - A Ariando
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
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Tiwari SK, Pandey SK, Pandey R, Wang N, Bystrzejewski M, Mishra YK, Zhu Y. Stone-Wales Defect in Graphene. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2303340. [PMID: 37386778 DOI: 10.1002/smll.202303340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Indexed: 07/01/2023]
Abstract
2D graphene the most investigated structures from nanocarbon family studied in the last three decades. It is projected as an excellent material useful for quantum computing, artificial intelligence, and next generation advanced technologies. Graphene exists in several forms and its extraordinary thermal, mechanical, and electronic properties, principally depend on the kind of perfection of the hexagonal atomic lattice. Defects are always considered as undesired components but certain defects in graphene could be an asset for electrochemistry and quantum electronics due to the engineered electronclouds and quantum tunnelling. The authors carefully discuss the Stone-Wales imperfections in graphene and its derivatives comprehensively. A specific emphasis is focused on the experimental and theoretical aspects of the Stone-Wales defects in graphene with respect to structure-property relationships. The corroboration of extrinsic defects like external atomic doping, functionalization, edge distortion in the graphene consisting of Stone-Wales imperfections, which are very significant in designing graphene-based electronic devices, are summarized.
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Affiliation(s)
- Santosh K Tiwari
- Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, Ministry of Education, School of Resources, Environment and Materials, Guangxi University, Nanning, 530004, China
- Department of Chemistry, NMAM Institute of Technology, Nitte (Deemed to be University), Mangaluru, Karnataka, 547110, India
| | - Sarvesh Kumar Pandey
- Department of Chemistry, School of Basic Sciences, Manipal University Jaipur, Jaipur, Rajasthan, 303007, India
| | - Raunak Pandey
- Department of Chemical Science and Engineering, Kathmandu University, Dhulikhel, 44600, Nepal
| | - Nannan Wang
- Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, Ministry of Education, School of Resources, Environment and Materials, Guangxi University, Nanning, 530004, China
| | | | - Yogendra Kumar Mishra
- Smart Materials, NanoSYD, Mads Clausen Institute, University of Southern Denmark, Alsion 2, Sønderborg, 6400, Denmark
| | - Yanqiu Zhu
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QF, UK
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Márkus BG, Gmitra M, Dóra B, Csősz G, Fehér T, Szirmai P, Náfrádi B, Zólyomi V, Forró L, Fabian J, Simon F. Ultralong 100 ns spin relaxation time in graphite at room temperature. Nat Commun 2023; 14:2831. [PMID: 37198155 DOI: 10.1038/s41467-023-38288-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 04/24/2023] [Indexed: 05/19/2023] Open
Abstract
Graphite has been intensively studied, yet its electron spins dynamics remains an unresolved problem even 70 years after the first experiments. The central quantities, the longitudinal (T1) and transverse (T2) relaxation times were postulated to be equal, mirroring standard metals, but T1 has never been measured for graphite. Here, based on a detailed band structure calculation including spin-orbit coupling, we predict an unexpected behavior of the relaxation times. We find, based on saturation ESR measurements, that T1 is markedly different from T2. Spins injected with perpendicular polarization with respect to the graphene plane have an extraordinarily long lifetime of 100 ns at room temperature. This is ten times more than in the best graphene samples. The spin diffusion length across graphite planes is thus expected to be ultralong, on the scale of ~ 70 μm, suggesting that thin films of graphite - or multilayer AB graphene stacks - can be excellent platforms for spintronics applications compatible with 2D van der Waals technologies. Finally, we provide a qualitative account of the observed spin relaxation based on the anisotropic spin admixture of the Bloch states in graphite obtained from density functional theory calculations.
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Affiliation(s)
- B G Márkus
- Stavropoulos Center for Complex Quantum Matter, Department of Physics and Astronomy, University of Notre Dame, Notre Dame, IN, 46556, USA
- Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Budapest, H-1525, Hungary
- Department of Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary
| | - M Gmitra
- Institute of Physics, Pavol Jozef Šafárik University in Košice, Park Angelinum 9, 040 01, Košice, Slovakia
- Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 04001, Košice, Slovakia
| | - B Dóra
- Department of Theoretical Physics, Institute of Physics and MTA-BME Lendület Topology and Correlation Research Group Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary
| | - G Csősz
- Department of Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary
| | - T Fehér
- Department of Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary
| | - P Szirmai
- Laboratory of Physics of Complex Matter, École Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
| | - B Náfrádi
- Laboratory of Physics of Complex Matter, École Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
| | - V Zólyomi
- STFC Hartree Centre, Daresbury Laboratory, Daresbury, Warrington WA4 4AD, UK
| | - L Forró
- Stavropoulos Center for Complex Quantum Matter, Department of Physics and Astronomy, University of Notre Dame, Notre Dame, IN, 46556, USA
- Laboratory of Physics of Complex Matter, École Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
| | - J Fabian
- Department of Physics, University of Regensburg, 93040, Regensburg, Germany.
| | - F Simon
- Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Budapest, H-1525, Hungary.
- Department of Physics, Institute of Physics and ELKH-BME Condensed Matter Research Group Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary.
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Aboljadayel ROM, Kinane CJ, Vaz CAF, Love DM, Weatherup RS, Braeuninger-Weimer P, Martin MB, Ionescu A, Caruana AJ, Charlton TR, Llandro J, Monteiro PMS, Barnes CHW, Hofmann S, Langridge S. Determining the Proximity Effect-Induced Magnetic Moment in Graphene by Polarized Neutron Reflectivity and X-ray Magnetic Circular Dichroism. ACS APPLIED MATERIALS & INTERFACES 2023; 15:22367-22376. [PMID: 37092734 PMCID: PMC10176321 DOI: 10.1021/acsami.2c02840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
We report the magnitude of the induced magnetic moment in CVD-grown epitaxial and rotated-domain graphene in proximity with a ferromagnetic Ni film, using polarized neutron reflectivity (PNR) and X-ray magnetic circular dichroism (XMCD). The XMCD spectra at the C K-edge confirm the presence of a magnetic signal in the graphene layer, and the sum rules give a magnetic moment of up to ∼0.47 μB/C atom induced in the graphene layer. For a more precise estimation, we conducted PNR measurements. The PNR results indicate an induced magnetic moment of ∼0.41 μB/C atom at 10 K for epitaxial and rotated-domain graphene. Additional PNR measurements on graphene grown on a nonmagnetic Ni9Mo1 substrate, where no magnetic moment in graphene is measured, suggest that the origin of the induced magnetic moment is due to the opening of the graphene's Dirac cone as a result of the strong C pz-Ni 3d hybridization.
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Affiliation(s)
- Razan O M Aboljadayel
- Cavendish Laboratory, Physics Department, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Christy J Kinane
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxon OX11 0QX, United Kingdom
| | - Carlos A F Vaz
- Swiss Light Source, Paul Scherrer Institut, Villigen PSI 5232, Switzerland
| | - David M Love
- Cavendish Laboratory, Physics Department, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Robert S Weatherup
- Department of Engineering, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | | | - Marie-Blandine Martin
- Department of Engineering, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - Adrian Ionescu
- Cavendish Laboratory, Physics Department, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Andrew J Caruana
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxon OX11 0QX, United Kingdom
| | - Timothy R Charlton
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxon OX11 0QX, United Kingdom
| | - Justin Llandro
- Cavendish Laboratory, Physics Department, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Pedro M S Monteiro
- Cavendish Laboratory, Physics Department, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Crispin H W Barnes
- Cavendish Laboratory, Physics Department, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Stephan Hofmann
- Department of Engineering, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - Sean Langridge
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxon OX11 0QX, United Kingdom
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5
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Belayadi A, Vasilopoulos P. A spin modulating device, tuned by the Fermi energy, in honeycomb-like substrates periodically stubbed with transition-metal-dichalkogenides. NANOTECHNOLOGY 2022; 34:085704. [PMID: 36301679 DOI: 10.1088/1361-6528/ac9d43] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 10/24/2022] [Indexed: 06/16/2023]
Abstract
We investigate spin transport through graphene-like substrates stubbed vertically with transition-metal-dichalcogenides (TMDs). A tight-binding model is used based on a graphene-like Hamiltonian that includes different types of spin-orbit coupling (SOC) terms permitted by theC3vsymmetry group in TMDs/graphene-like heterostructures. The results show a spin modulation obtained by tuning the strength and sign of the Fermi energyEFand not by varying the SOC strength as is mainly the case of Datta and Das. The spin conductance is directly controlled by the value ofEF. In addition, a perfect electron-spin modulation is obtained when a vertical strain is introduced. In this case, the spin conductance exhibits a strong energy dependence. The results may open the route to a combination of graphene-like substrates with TMD stubs and the development of spin-transistor devices controlled by the Fermi energy rather than the SOC strength.
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Affiliation(s)
- Adel Belayadi
- Department of Physics, Ecole Supérieure des Sciences des Aliments et Industrie Alimentaire, ESSAIA, El Harrach, Algeria
- Department of Physics, University of Science And Technology Houari Boumediene, Bab-Ezzouar, Algeria
| | - Panagiotis Vasilopoulos
- Department of Physics, Concordia University, 7141 Sherbrooke Ouest, Montral, Qubec, H4B 1R6, Canada
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6
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Tseng CC, Song T, Jiang Q, Lin Z, Wang C, Suh J, Watanabe K, Taniguchi T, McGuire MA, Xiao D, Chu JH, Cobden DH, Xu X, Yankowitz M. Gate-Tunable Proximity Effects in Graphene on Layered Magnetic Insulators. NANO LETTERS 2022; 22:8495-8501. [PMID: 36279401 DOI: 10.1021/acs.nanolett.2c02931] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The extreme versatility of van der Waals materials originates from their ability to exhibit new electronic properties when assembled in close proximity to dissimilar crystals. For example, although graphene is inherently nonmagnetic, recent work has reported a magnetic proximity effect in graphene interfaced with magnetic substrates, potentially enabling a pathway toward achieving a high-temperature quantum anomalous Hall effect. Here, we investigate heterostructures of graphene and chromium trihalide magnetic insulators (CrI3, CrBr3, and CrCl3). Surprisingly, we are unable to detect a magnetic exchange field in the graphene but instead discover proximity effects featuring unprecedented gate tunability. The graphene becomes highly hole-doped due to charge transfer from the neighboring magnetic insulator and further exhibits a variety of atypical gate-dependent transport features. The charge transfer can additionally be altered upon switching the magnetic states of the nearest CrI3 layers. Our results provide a roadmap for exploiting proximity effects arising in graphene coupled to magnetic insulators.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Michael A McGuire
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Di Xiao
- Pacific Northwest National Laboratory, Richland, Washington99354, United States
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7
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Alsharari AM, Ulloa SE. Inducing chiral superconductivity on honeycomb lattice systems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:205403. [PMID: 35235911 DOI: 10.1088/1361-648x/ac5a03] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 03/02/2022] [Indexed: 06/14/2023]
Abstract
Superconductivity in graphene-based systems has recently attracted much attention, as either intrinsic behavior or induced by proximity to a superconductor may lead to interesting topological phases and symmetries of the pairing function. A prominent system considers the pairing to have chiral symmetry. The question arises as to the effect of possible spin-orbit coupling on the resulting superconducting quasiparticle (QP) spectrum. Utilizing a Bogolyubov-de Gennes (BdG) Hamiltonian, we explore the interplay of different interaction terms in the system, and their role in generating complex Berry curvatures in the QP spectrum, as well as non-trivial topological behavior. We demonstrate that the topology of the BdG Hamiltonian in these systems may result in the appearance of edge states along the zigzag edges of nanoribbons in the appropriate regime. For suitable chemical potential and superconducting pairing strength, we find the appearance of robust midgap states at zigzag edges, well protected by large excitation gaps and momentum transfer.
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Affiliation(s)
| | - Sergio E Ulloa
- Department of Physics and Astronomy, and Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, OH 45701, United States of America
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
- Center for Nanostructured Graphene, DTU Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
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8
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Zollner K, Fabian J. Engineering Proximity Exchange by Twisting: Reversal of Ferromagnetic and Emergence of Antiferromagnetic Dirac Bands in Graphene/Cr_{2}Ge_{2}Te_{6}. PHYSICAL REVIEW LETTERS 2022; 128:106401. [PMID: 35333087 DOI: 10.1103/physrevlett.128.106401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 12/22/2021] [Accepted: 02/17/2022] [Indexed: 06/14/2023]
Abstract
We investigate the twist-angle and gate dependence of the proximity exchange coupling in twisted graphene on monolayer Cr_{2}Ge_{2}Te_{6} from first principles. The proximitized Dirac band dispersions of graphene are fitted to a model Hamiltonian, yielding effective sublattice-resolved proximity-induced exchange parameters (λ_{ex}^{A} and λ_{ex}^{B}) for a series of twist angles between 0° and 30°. For aligned layers (0° twist angle), the exchange coupling of graphene is the same on both sublattices, λ_{ex}^{A}≈λ_{ex}^{B}≈4 meV, while the coupling is reversed at 30° (with λ_{ex}^{A}≈λ_{ex}^{B}≈-4 meV). Remarkably, at 19.1° the induced exchange coupling becomes antiferromagnetic: λ_{ex}^{A}<0, λ_{ex}^{B}>0. Further tuning is provided by a transverse electric field and the interlayer distance. The predicted proximity magnetization reversal and emergence of an antiferromagnetic Dirac dispersion make twisted graphene/Cr_{2}Ge_{2}Te_{6} bilayers a versatile platform for realizing topological phases and for spintronics applications.
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Affiliation(s)
- Klaus Zollner
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Jaroslav Fabian
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
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9
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Sierra JF, Fabian J, Kawakami RK, Roche S, Valenzuela SO. Van der Waals heterostructures for spintronics and opto-spintronics. NATURE NANOTECHNOLOGY 2021; 16:856-868. [PMID: 34282312 DOI: 10.1038/s41565-021-00936-x] [Citation(s) in RCA: 107] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Accepted: 06/03/2021] [Indexed: 06/13/2023]
Abstract
The large variety of 2D materials and their co-integration in van der Waals heterostructures enable innovative device engineering. In addition, their atomically thin nature promotes the design of artificial materials by proximity effects that originate from short-range interactions. Such a designer approach is particularly compelling for spintronics, which typically harnesses functionalities from thin layers of magnetic and non-magnetic materials and the interfaces between them. Here we provide an overview of recent progress in 2D spintronics and opto-spintronics using van der Waals heterostructures. After an introduction to the forefront of spin transport research, we highlight the unique spin-related phenomena arising from spin-orbit and magnetic proximity effects. We further describe the ability to create multifunctional hybrid heterostructures based on van der Waals materials, combining spin, valley and excitonic degrees of freedom. We end with an outlook on perspectives and challenges for the design and production of ultracompact all-2D spin devices and their potential applications in conventional and quantum technologies.
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Affiliation(s)
- Juan F Sierra
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.
| | - Jaroslav Fabian
- Institute for Theoretical Physics, University of Regensburg, Regensburg, Germany
| | | | - Stephan Roche
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
| | - Sergio O Valenzuela
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.
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10
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Crasto de Lima F, Fazzio A. Bandgap evolution in nanographene assemblies. Phys Chem Chem Phys 2021; 23:11501-11506. [PMID: 33960330 DOI: 10.1039/d1cp01030a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Recently cycloarene has been experimentally obtained in a self-assembled structure, forming graphene-like monoatomic layered systems. Here, we established bandgap engineering/prediction in cycloarene assemblies within a combination of density functional theory and tight-binding Hamiltonians. Our results show that the inter-molecule bond density rules the bandgap. The increase in such bond density increases the valence/conduction bandwidth decreasing the energy gap linearly. We derived an effective model that allows the interpretation of the arising energy gap for general particle-hole symmetric molecular arrangements based on inter-molecular bond strength.
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Affiliation(s)
- F Crasto de Lima
- Brazilian Nanotechnology National Laboratory (LNNano), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-970, Campinas, SP, Brazil.
| | - A Fazzio
- Brazilian Nanotechnology National Laboratory (LNNano), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-970, Campinas, SP, Brazil.
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11
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Luo M. Optically induced topological phase transition in two dimensional square lattice antiferromagnet. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 33:055501. [PMID: 33065570 DOI: 10.1088/1361-648x/abc1ff] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 10/16/2020] [Indexed: 06/11/2023]
Abstract
The two dimensional square lattice antiferromagnet with spin-orbit coupling and nonsymmorphic symmetry is recently found to be topological insulator (TI). We theoretically studied the Floquet states of the antiferromagnetic crystal with optical irradiation, which could be applicable in opto-spintronic. An optical irradiation with circular polarization induces topological phase transition into quantum Anomalous Hall phase with varying Chern number. At the phase boundaries, the Floquet systems could be semimetal with one, two or three band valleys. A linear polarized optical field induces effective antiferromagnetic exchange field, which change the phase regime of the TI. At the intersection of two phase boundaries, the bulk band structure is nearly flat along one of the high symmetry line in the first Brillouin zone, which result in large density of states near to the Fermi energy in bulk and nanoribbons.
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Affiliation(s)
- Ma Luo
- The State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou, 510275, People's Republic of China
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