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Gao X, Ma C, Li L, Zhang X, Deng Z, Li X, Zhou Z. Controlling the spin current around the rectangular cavities in two-dimensional topological insulators. Phys Chem Chem Phys 2024; 26:3597-3604. [PMID: 38214895 DOI: 10.1039/d3cp04648f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2024]
Abstract
Controlling spin current in topological insulators (TIs) is a crucial requirement for applications in quantum computing and spintronics. Using the non-equilibrium Keldysh Green's function formalism, we demonstrate that such control can be established around rectangular cavities of two-dimensional TIs by breaking their time reversal symmetry via exchange magnetic fields and magnetic defects. In the presence of magnetic defects with xy symmetry or Ising symmetry, the density of states is localized, and the spin current forms a current loop around the rectangular cavity in TIs interfacing with two ferromagnetic stripes. We also observe that the spin direction of the traveling electrons is inverted under the reversal of bias and gate voltages. The change in the spin-polarized current around the cavities is predicted by varying the strength of Rashba spin-orbit coupling. This result allows for the creation and control of nearly fully spin-polarized currents with various spatial patterns around the cavities in TIs, and the design of tunable spin diodes for highly integrated spintronics.
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Affiliation(s)
- Xiang Gao
- Joint Laboratory for Extreme Conditions Matter Properties, Southwest University of Science and Technology, Mianyang 621010, China
| | - Cheng Ma
- Joint Laboratory for Extreme Conditions Matter Properties, Southwest University of Science and Technology, Mianyang 621010, China
| | - Lei Li
- College of Physics and Electronic Information, Sichuan University of Science and Engineering, Yibin 644000, China.
| | - Xiaowei Zhang
- State Key Laboratory of Environment-Friendly Energy Materials, Southwest University of Science and Technology, Mianyang 621010, China
| | - Zhihong Deng
- Joint Laboratory for Extreme Conditions Matter Properties, Southwest University of Science and Technology, Mianyang 621010, China
| | - Xu Li
- Joint Laboratory for Extreme Conditions Matter Properties, Southwest University of Science and Technology, Mianyang 621010, China
| | - Zigang Zhou
- Joint Laboratory for Extreme Conditions Matter Properties, Southwest University of Science and Technology, Mianyang 621010, China
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2
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Muñiz Cano B, Ferreiros Y, Pantaleón PA, Dai J, Tallarida M, Figueroa AI, Marinova V, García-Díez K, Mugarza A, Valenzuela SO, Miranda R, Camarero J, Guinea F, Silva-Guillén JA, Valbuena MA. Experimental Demonstration of a Magnetically Induced Warping Transition in a Topological Insulator Mediated by Rare-Earth Surface Dopants. NANO LETTERS 2023. [PMID: 37156508 DOI: 10.1021/acs.nanolett.3c00587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Magnetic topological insulators constitute a novel class of materials whose topological surface states (TSSs) coexist with long-range ferromagnetic order, eventually breaking time-reversal symmetry. The subsequent bandgap opening is predicted to co-occur with a distortion of the TSS warped shape from hexagonal to trigonal. We demonstrate such a transition by means of angle-resolved photoemission spectroscopy on the magnetically rare-earth (Er and Dy) surface-doped topological insulator Bi2Se2Te. Signatures of the gap opening are also observed. Moreover, increasing the dopant coverage results in a tunable p-type doping of the TSS, thereby allowing for a gradual tuning of the Fermi level toward the magnetically induced bandgap. A theoretical model where a magnetic Zeeman out-of-plane term is introduced in the Hamiltonian governing the TSS rationalizes these experimental results. Our findings offer new strategies to control magnetic interactions with TSSs and open up viable routes for the realization of the quantum anomalous Hall effect.
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Affiliation(s)
- Beatriz Muñiz Cano
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
| | - Yago Ferreiros
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
| | - Pierre A Pantaleón
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
| | - Ji Dai
- ALBA Synchrotron Light Source, Cerdanyola del Vallès, 08290 Barcelona, Spain
| | - Massimo Tallarida
- ALBA Synchrotron Light Source, Cerdanyola del Vallès, 08290 Barcelona, Spain
| | - Adriana I Figueroa
- Departament de Física de la Matéria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, 08193 Barcelona, Spain
| | - Vera Marinova
- Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences, Acad. G. Bontchev, Str. 109, 1113 Sofia, Bulgaria
| | - Kevin García-Díez
- ALBA Synchrotron Light Source, Cerdanyola del Vallès, 08290 Barcelona, Spain
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, 08193 Barcelona, Spain
| | - Aitor Mugarza
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, 08193 Barcelona, Spain
- ICREA Institució Catalana de Recerca i Estudis Avançats, Lluis Companys 23, 08010 Barcelona, Spain
| | - Sergio O Valenzuela
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, 08193 Barcelona, Spain
- ICREA Institució Catalana de Recerca i Estudis Avançats, Lluis Companys 23, 08010 Barcelona, Spain
| | - Rodolfo Miranda
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
- Departamento de Física de la Materia Condensada, Instituto "Nicolás Cabrera" and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid (UAM), Campus de Cantoblanco, 28049 Madrid, Spain
| | - Julio Camarero
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
- Departamento de Física de la Materia Condensada, Instituto "Nicolás Cabrera" and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid (UAM), Campus de Cantoblanco, 28049 Madrid, Spain
| | - Francisco Guinea
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
- Donostia International Physics Center, Paseo Manuel de Lardizábal 4, 20018 San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48009 Bilbao, Spain
| | - Jose Angel Silva-Guillén
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
| | - Miguel A Valbuena
- Instituto Madrileño de Estudios Avanzados, IMDEA Nanociencia, Calle Faraday 9, 28049 Madrid, Spain
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McLaughlin NJ, Hu C, Huang M, Zhang S, Lu H, Yan GQ, Wang H, Tserkovnyak Y, Ni N, Du CR. Quantum Imaging of Magnetic Phase Transitions and Spin Fluctuations in Intrinsic Magnetic Topological Nanoflakes. NANO LETTERS 2022; 22:5810-5817. [PMID: 35816128 DOI: 10.1021/acs.nanolett.2c01390] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Topological materials featuring exotic band structures, unconventional current flow patterns, and emergent organizing principles offer attractive platforms for the development of next-generation transformative quantum electronic technologies. The family of MnBi2Te4 (Bi2Te3)n materials is naturally relevant in this context due to their nontrivial band topology, tunable magnetism, and recently discovered extraordinary quantum transport behaviors. Despite numerous pioneering studies to date, the local magnetic properties of MnBi2Te4 (Bi2Te3)n remain an open question, hindering a comprehensive understanding of their fundamental material properties. Exploiting nitrogen-vacancy (NV) centers in diamond, we report nanoscale quantum imaging of the magnetic phase transitions and spin fluctuations in exfoliated MnBi4Te7 flakes, revealing the underlying spin transport physics and magnetic domains at the nanoscale. Our results highlight the unique advantage of NV centers in exploring the magnetic properties of emergent quantum materials, opening new opportunities for investigating the interplay between topology and magnetism.
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Affiliation(s)
- Nathan J McLaughlin
- Department of Physics, University of California, San Diego, La Jolla, California 92093, United States
| | - Chaowei Hu
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, United States
| | - Mengqi Huang
- Department of Physics, University of California, San Diego, La Jolla, California 92093, United States
| | - Shu Zhang
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, United States
| | - Hanyi Lu
- Department of Physics, University of California, San Diego, La Jolla, California 92093, United States
| | - Gerald Q Yan
- Department of Physics, University of California, San Diego, La Jolla, California 92093, United States
| | - Hailong Wang
- Center for Memory and Recording Research, University of California, San Diego, La Jolla, California 92093, United States
| | - Yaroslav Tserkovnyak
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, United States
| | - Ni Ni
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, United States
| | - Chunhui Rita Du
- Department of Physics, University of California, San Diego, La Jolla, California 92093, United States
- Center for Memory and Recording Research, University of California, San Diego, La Jolla, California 92093, United States
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Riddiford LJ, Grutter AJ, Pillsbury T, Stanley M, Reifsnyder Hickey D, Li P, Alem N, Samarth N, Suzuki Y. Understanding Signatures of Emergent Magnetism in Topological Insulator/Ferrite Bilayers. PHYSICAL REVIEW LETTERS 2022; 128:126802. [PMID: 35394317 DOI: 10.1103/physrevlett.128.126802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 01/21/2022] [Accepted: 02/23/2022] [Indexed: 06/14/2023]
Abstract
Magnetic insulator-topological insulator heterostructures have been studied in search of chiral edge states via proximity induced magnetism in the topological insulator, but these states have been elusive. We identified MgAl_{0.5}Fe_{1.5}O_{4}/Bi_{2}Se_{3} bilayers for a possible magnetic proximity effect. Electrical transport and polarized neutron reflectometry suggest a proximity effect, but structural data indicate a disordered interface as the origin of the magnetic response. Our results provide a strategy via correlation of microstructure with magnetic data to confirm a magnetic proximity effect.
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Affiliation(s)
- Lauren J Riddiford
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
| | - Alexander J Grutter
- National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Timothy Pillsbury
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Max Stanley
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Danielle Reifsnyder Hickey
- Department of Materials Science, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Peng Li
- Department of Electrical Engineering and Computer Science, Auburn University, Auburn University, Auburn, Alabama 36849, USA
| | - Nasim Alem
- Department of Materials Science, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Nitin Samarth
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Yuri Suzuki
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
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5
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Liu J, Hesjedal T. Magnetic Topological Insulator Heterostructures: A Review. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021:e2102427. [PMID: 34665482 DOI: 10.1002/adma.202102427] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 06/05/2021] [Indexed: 06/13/2023]
Abstract
Topological insulators (TIs) provide intriguing prospects for the future of spintronics due to their large spin-orbit coupling and dissipationless, counter-propagating conduction channels in the surface state. The combination of topological properties and magnetic order can lead to new quantum states including the quantum anomalous Hall effect that was first experimentally realized in Cr-doped (Bi,Sb)2 Te3 films. Since magnetic doping can introduce detrimental effects, requiring very low operational temperatures, alternative approaches are explored. Proximity coupling to magnetically ordered systems is an obvious option, with the prospect to raise the temperature for observing the various quantum effects. Here, an overview of proximity coupling and interfacial effects in TI heterostructures is presented, which provides a versatile materials platform for tuning the magnetic and topological properties of these exciting materials. An introduction is first given to the heterostructure growth by molecular beam epitaxy and suitable structural, electronic, and magnetic characterization techniques. Going beyond transition-metal-doped and undoped TI heterostructures, examples of heterostructures are discussed, including rare-earth-doped TIs, magnetic insulators, and antiferromagnets, which lead to exotic phenomena such as skyrmions and exchange bias. Finally, an outlook on novel heterostructures such as intrinsic magnetic TIs and systems including 2D materials is given.
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Affiliation(s)
- Jieyi Liu
- Clarendon Laboratory, Department of Physics University of Oxford, Parks Road, Oxford, OX1 3PU, UK
| | - Thorsten Hesjedal
- Clarendon Laboratory, Department of Physics University of Oxford, Parks Road, Oxford, OX1 3PU, UK
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Bhattacharyya S, Akhgar G, Gebert M, Karel J, Edmonds MT, Fuhrer MS. Recent Progress in Proximity Coupling of Magnetism to Topological Insulators. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2007795. [PMID: 34185344 DOI: 10.1002/adma.202007795] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 01/11/2021] [Indexed: 05/08/2023]
Abstract
Inducing long-range magnetic order in 3D topological insulators can gap the Dirac-like metallic surface states, leading to exotic new phases such as the quantum anomalous Hall effect or the axion insulator state. These magnetic topological phases can host robust, dissipationless charge and spin currents or unique magnetoelectric behavior, which can be exploited in low-energy electronics and spintronics applications. Although several different strategies have been successfully implemented to realize these states, to date these phenomena have been confined to temperatures below a few Kelvin. This review focuses on one strategy: inducing magnetic order in topological insulators by proximity of magnetic materials, which has the capability for room temperature operation, unlocking the potential of magnetic topological phases for applications. The unique advantages of this strategy, the important physical mechanisms facilitating magnetic proximity effect, and the recent progress to achieve, understand, and harness proximity-coupled magnetic order in topological insulators are discussed. Some emerging new phenomena and applications enabled by proximity coupling of magnetism and topological materials, such as skyrmions and the topological Hall effect, are also highlighted, and the authors conclude with an outlook on remaining challenges and opportunities in the field.
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Affiliation(s)
- Semonti Bhattacharyya
- School of Physics and Astronomy, Monash University, Victoria, 3800, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Victoria, 3800, Australia
| | - Golrokh Akhgar
- School of Physics and Astronomy, Monash University, Victoria, 3800, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Victoria, 3800, Australia
| | - Matthew Gebert
- School of Physics and Astronomy, Monash University, Victoria, 3800, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Victoria, 3800, Australia
| | - Julie Karel
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Victoria, 3800, Australia
- Department of Materials Science and Engineering, Monash University, Clayton, Victoria, 3800, Australia
| | - Mark T Edmonds
- School of Physics and Astronomy, Monash University, Victoria, 3800, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Victoria, 3800, Australia
| | - Michael S Fuhrer
- School of Physics and Astronomy, Monash University, Victoria, 3800, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Victoria, 3800, Australia
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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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