1
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Li Y, Chan YH, Hlevyack JA, Bowers JW, Chou MY, Chiang TC. Topological Quantum Well States in Pb/Sb Thin-Film Heterostructures. ACS NANO 2024; 18:10243-10248. [PMID: 38530641 PMCID: PMC11008363 DOI: 10.1021/acsnano.4c00724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 03/12/2024] [Accepted: 03/21/2024] [Indexed: 03/28/2024]
Abstract
Composite topological heterostructures, wherein topologically protected states are electronically tuned due to their proximity to other matter, are key avenues for exploring emergent physical phenomena. Particularly, pairing a topological material with a superconductor such as Pb is a promising means for generating a topological superconducting phase with exotic Majorana quasiparticles, but oft-neglected is the emergence of bulklike spin-polarized states that are quite relevant to applications. Using high-resolution photoemission spectroscopy and first-principles calculations, we report the emergence of bulk-like spin-polarized topological quantum well states with long coherence lengths in Pb films grown on the topological semimetal Sb. The results establish Pb/Sb heterostructures as topological superconductor candidates and advance the current understanding of topological coupling effects required for realizing emergent physics and for designing advanced spintronic device architectures.
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Affiliation(s)
- Yao Li
- Department
of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois Urbana−Champaign; Urbana, Illinois 61801, United States
| | - Yang-hao Chan
- Institute
of Atomic and Molecular Sciences, Academia
Sinica, Taipei 10617, Taiwan
- Physics
Division, National Center for Theoretical
Sciences, Taipei 10617, Taiwan
| | - Joseph A. Hlevyack
- Department
of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois Urbana−Champaign; Urbana, Illinois 61801, United States
| | - John W. Bowers
- Department
of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois Urbana−Champaign; Urbana, Illinois 61801, United States
| | - Mei-Yin Chou
- Institute
of Atomic and Molecular Sciences, Academia
Sinica, Taipei 10617, Taiwan
- Department
of Physics, National Taiwan University, Taipei 10617, Taiwan
| | - Tai-Chang Chiang
- Department
of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois Urbana−Champaign; Urbana, Illinois 61801, United States
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2
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Sattigeri RM, Cuono G, Autieri C. Altermagnetic surface states: towards the observation and utilization of altermagnetism in thin films, interfaces and topological materials. NANOSCALE 2023; 15:16998-17005. [PMID: 37831060 DOI: 10.1039/d3nr03681b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/14/2023]
Abstract
The altermagnetism influences the electronic states allowing the presence of non-relativistic spin-splittings. Since altermagnetic spin-splitting is present along specific k-paths of the 3D Brillouin zone, we expect that the altermagnetic surface stateswill be present on specific surface orientations. We unveil the properties of the altermagnetic surface states considering three representative materials belonging to the orthorhombic, hexagonal and tetragonal space groups. We calculate the 2D projected Brillouin zone from the 3D Brillouin zone. We study the surfaces with their respective 2D Brillouin zones establishing where the spin-splittings with opposite sign merge annihilating the altermagnetic properties and on which surfaces the altermagnetism is preserved. Looking at the three principal surface orientations, we find that for several cases two surfaces are blind to the altermagnetism, while the altermagnetism survives for one surface orientation. Which surface preserves the altermagnetism depends also on themagnetic order. We qualitatively show that an electric field orthogonal to the blind surface can activate the altermagnetism. Our projection method was proven for strong altermagnetism, but it will be equivalently valid for recently discovered weak altermagnetism. Our results predict which surfaces to cleave in order to preserve altermagnetism in surfaces or interfaces and this paves the way to observe non-relativistic altermagnetic spin-splitting in thin films via spin-resolved ARPES and to interface the altermagnetism with other collective modes. We open future perspectives for the study of altermagnetic effects on the trivial and topological surface states.
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Affiliation(s)
- Raghottam M Sattigeri
- International Research Centre Magtop, Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, PL-02668 Warsaw, Poland.
| | - Giuseppe Cuono
- International Research Centre Magtop, Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, PL-02668 Warsaw, Poland.
| | - Carmine Autieri
- International Research Centre Magtop, Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, PL-02668 Warsaw, Poland.
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3
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Cho SW, Lee IH, Lee Y, Kim S, Khim YG, Park SY, Jo Y, Choi J, Han S, Chang YJ, Lee S. Investigation of the mechanism of the anomalous Hall effects in Cr 2Te 3/(BiSb) 2(TeSe) 3 heterostructure. NANO CONVERGENCE 2023; 10:2. [PMID: 36625963 PMCID: PMC9832196 DOI: 10.1186/s40580-022-00348-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 11/28/2022] [Indexed: 06/17/2023]
Abstract
The interplay between ferromagnetism and the non-trivial topology has unveiled intriguing phases in the transport of charges and spins. For example, it is consistently observed the so-called topological Hall effect (THE) featuring a hump structure in the curve of the Hall resistance (Rxy) vs. a magnetic field (H) of a heterostructure consisting of a ferromagnet (FM) and a topological insulator (TI). The origin of the hump structure is still controversial between the topological Hall effect model and the multi-component anomalous Hall effect (AHE) model. In this work, we have investigated a heterostructure consisting of BixSb2-xTeySe3-y (BSTS) and Cr2Te3 (CT), which are well-known TI and two-dimensional FM, respectively. By using the so-called "minor-loop measurement", we have found that the hump structure observed in the CT/BSTS is more likely to originate from two AHE channels. Moreover, by analyzing the scaling behavior of each amplitude of two AHE with the longitudinal resistivities of CT and BSTS, we have found that one AHE is attributed to the extrinsic contribution of CT while the other is due to the intrinsic contribution of BSTS. It implies that the proximity-induced ferromagnetic layer inside BSTS serves as a source of the intrinsic AHE, resulting in the hump structure explained by the two AHE model.
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Affiliation(s)
- Seong Won Cho
- Center for Neuromorphic engineering, Korea Institute of Science and Technology, Seoul, 02792, Korea
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Korea
| | - In Hak Lee
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, Korea
| | - Youngwoong Lee
- Center for Neuromorphic engineering, Korea Institute of Science and Technology, Seoul, 02792, Korea
- Department of Physics, Konkuk University, Seoul, 05029, Korea
| | - Sangheon Kim
- Center for Neuromorphic engineering, Korea Institute of Science and Technology, Seoul, 02792, Korea
- Department of Materials Science and Engineering, Korea University, Seoul, 02841, Korea
| | - Yeong Gwang Khim
- Department of Physics, University of Seoul, Seoul, 02504, Korea
- Department of Smart Cities, University of Seoul, Seoul, 02504, Korea
| | - Seung-Young Park
- Center for Scientific Instrumentation, Korea Basic Science Institute, Daejeon, 34133, Korea
| | - Younghun Jo
- Center for Scientific Instrumentation, Korea Basic Science Institute, Daejeon, 34133, Korea
| | - Junwoo Choi
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, Korea
| | - Seungwu Han
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Korea
| | - Young Jun Chang
- Department of Physics, University of Seoul, Seoul, 02504, Korea
- Department of Smart Cities, University of Seoul, Seoul, 02504, Korea
| | - Suyoun Lee
- Center for Neuromorphic engineering, Korea Institute of Science and Technology, Seoul, 02792, Korea.
- Division of Nano & Information Technology, Korea University of Science and Technology, Daejeon, 34316, Korea.
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4
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Akiyama R, Ishikawa R, Akutsu-Suyama K, Nakanishi R, Tomohiro Y, Watanabe K, Iida K, Mitome M, Hasegawa S, Kuroda S. Direct Probe of the Ferromagnetic Proximity Effect at the Interface of SnTe/Fe Heterostructure by Polarized Neutron Reflectometry. J Phys Chem Lett 2022; 13:8228-8235. [PMID: 36031713 DOI: 10.1021/acs.jpclett.2c01478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Introducing magnetic order into a topological insulator (TI) system has attracted much attention with an expectation of realizing exotic phenomena such as the quantum anomalous Hall effect (QAHE) and axion insulator states. The magnetic proximity effect (MPE) is one of the promising schemes to induce the magnetic order on the surface of a TI without introducing disorder accompanied by doping magnetic impurities in the TI. In this study, we investigate the MPE at the interface of a heterostructure consisting of the topological crystalline insulator (TCI) SnTe and Fe by employing polarized neutron reflectometry. The ferromagnetic order penetrates ∼2.2 nm deep into the SnTe layer from the interface with Fe, which persists up to room temperature. This is induced by the MPE on the surface of the TCI preserving the coherent topological states without introducing the disorder by doping magnetic impurities. This would open up a way for realizing next-generation spintronics and quantum computational devices.
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Affiliation(s)
- Ryota Akiyama
- Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Ryo Ishikawa
- Institute of Materials Science, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8573, Japan
| | - Kazuhiro Akutsu-Suyama
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), 162-1 Shirakata, Tokai, Ibaraki 319-1106, Japan
| | - Ryosuke Nakanishi
- Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Yuta Tomohiro
- Institute of Materials Science, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8573, Japan
| | - Kazumi Watanabe
- Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Kazuki Iida
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), 162-1 Shirakata, Tokai, Ibaraki 319-1106, Japan
| | - Masanori Mitome
- Electron Microscopy Analysis Station, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Shuji Hasegawa
- Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Shinji Kuroda
- Institute of Materials Science, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8573, Japan
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5
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Khomitsky DV, Konakov AA, Lavrukhina EA. Formation of bound states from the edge states of 2D topological insulator by macroscopic magnetic barriers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:405302. [PMID: 35878600 DOI: 10.1088/1361-648x/ac8407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2022] [Accepted: 07/25/2022] [Indexed: 06/15/2023]
Abstract
A model of bound state formation from the delocalized edge states of 2D topological insulator (TI) is derived by considering the effects of magnetic barriers attached to the edge of the HgTe/CdTe quantum well. The resulting structure has a spatial form of 1D quantum dot (QD) with variable number of bound states depending on barrier parameters. The spatial profile of exchange interaction between the edge states and barriers is derived from the interaction with single impurity magnetic moment and is generalized for the barrier bulk structure formed by ensemble of impurities. The resulting Hamiltonian is studied as a function of barrier parameters including their strength and orientation of the magnetic moments. It is shown that for parallel magnetization of two barriers at least two discrete levels are formed regardless of the barrier strength. For antiparallel magnetization at least a single bound state is formed for any strength of the barriers. Our results may help in design of novel types of QDs based on TIs.
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Affiliation(s)
- D V Khomitsky
- Department of Physics, National Research Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia
| | - A A Konakov
- Department of Physics, National Research Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia
| | - E A Lavrukhina
- Department of Physics, National Research Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia
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6
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Choi E, Sim KI, Burch KS, Lee YH. Emergent Multifunctional Magnetic Proximity in van der Waals Layered Heterostructures. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2200186. [PMID: 35596612 PMCID: PMC9313546 DOI: 10.1002/advs.202200186] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 04/01/2022] [Indexed: 05/10/2023]
Abstract
Proximity effect, which is the coupling between distinct order parameters across interfaces of heterostructures, has attracted immense interest owing to the customizable multifunctionalities of diverse 3D materials. This facilitates various physical phenomena, such as spin order, charge transfer, spin torque, spin density wave, spin current, skyrmions, and Majorana fermions. These exotic physics play important roles for future spintronic applications. Nevertheless, several fundamental challenges remain for effective applications: unavoidable disorder and lattice mismatch limits in the growth process, short characteristic length of proximity, magnetic fluctuation in ultrathin films, and relatively weak spin-orbit coupling (SOC). Meanwhile, the extensive library of atomically thin, 2D van der Waals (vdW) layered materials, with unique characteristics such as strong SOC, magnetic anisotropy, and ultraclean surfaces, offers many opportunities to tailor versatile and more effective functionalities through proximity effects. Here, this paper focuses on magnetic proximity, i.e., proximitized magnetism and reviews the engineering of magnetism-related functionalities in 2D vdW layered heterostructures for next-generation electronic and spintronic devices. The essential factors of magnetism and interfacial engineering induced by magnetic layers are studied. The current limitations and future challenges associated with magnetic proximity-related physics phenomena in 2D heterostructures are further discussed.
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Affiliation(s)
- Eun‐Mi Choi
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS)Sungkyunkwan University (SKKU)Suwon16419Republic of Korea
| | - Kyung Ik Sim
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS)Sungkyunkwan University (SKKU)Suwon16419Republic of Korea
| | - Kenneth S. Burch
- Department of PhysicsBoston College140 Commonwealth AveChestnut HillMA02467‐3804USA
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS)Sungkyunkwan University (SKKU)Suwon16419Republic of Korea
- Department of Energy ScienceSungkyunkwan UniversitySuwon16419Republic of Korea
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7
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Bhattacharjee N, Mahalingam K, Fedorko A, Lauter V, Matzelle M, Singh B, Grutter A, Will-Cole A, Page M, McConney M, Markiewicz R, Bansil A, Heiman D, Sun NX. Topological Antiferromagnetic Van der Waals Phase in Topological Insulator/Ferromagnet Heterostructures Synthesized by a CMOS-Compatible Sputtering Technique. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2108790. [PMID: 35132680 DOI: 10.1002/adma.202108790] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 01/30/2022] [Indexed: 06/14/2023]
Abstract
Breaking time-reversal symmetry by introducing magnetic order, thereby opening a gap in the topological surface state bands, is essential for realizing useful topological properties such as the quantum anomalous Hall and axion insulator states. In this work, a novel topological antiferromagnetic (AFM) phase is created at the interface of a sputtered, c-axis-oriented, topological insulator/ferromagnet heterostructure-Bi2 Te3 /Ni80 Fe20 because of diffusion of Ni in Bi2 Te3 (Ni-Bi2 Te3 ). The AFM property of the Ni-Bi2 Te3 interfacial layer is established by observation of spontaneous exchange bias in the magnetic hysteresis loop and compensated moments in the depth profile of the magnetization using polarized neutron reflectometry. Analysis of the structural and chemical properties of the Ni-Bi2 Te3 layer is carried out using selected-area electron diffraction, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy. These studies, in parallel with first-principles calculations, indicate a solid-state chemical reaction that leads to the formation of Ni-Te bonds and the presence of topological antiferromagnetic (AFM) compound NiBi2 Te4 in the Ni-Bi2 Te3 interface layer. The Neél temperature of the Ni-Bi2 Te3 layer is ≈63 K, which is higher than that of typical magnetic topological insulators (MTIs). The presented results provide a pathway toward industrial complementary metal-oxide-semiconductor (CMOS)-process-compatible sputtered-MTI heterostructures, leading to novel materials for topological quantum devices.
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Affiliation(s)
- Nirjhar Bhattacharjee
- Northeastern University, Department of Electrical and Computer Engineering, Boston, MA, 02115, USA
| | - Krishnamurthy Mahalingam
- Air Force Research Laboratory, Nano-electronic Materials Branch, Wright Patterson Air Force Base, Boston, OH, 05433, USA
| | - Adrian Fedorko
- Northeastern University, Department of Physics, Boston, MA, 02115, USA
| | - Valeria Lauter
- Quantum Condensed Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Boston, TN, 37831, USA
| | - Matthew Matzelle
- Northeastern University, Department of Physics, Boston, MA, 02115, USA
| | - Bahadur Singh
- Tata Institute of Fundamental Research, Department of Condensed Matter Physics and Materials Science, Mumbai, 400005, India
| | - Alexander Grutter
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Alexandria Will-Cole
- Northeastern University, Department of Electrical and Computer Engineering, Boston, MA, 02115, USA
| | - Michael Page
- Air Force Research Laboratory, Nano-electronic Materials Branch, Wright Patterson Air Force Base, Boston, OH, 05433, USA
| | - Michael McConney
- Air Force Research Laboratory, Nano-electronic Materials Branch, Wright Patterson Air Force Base, Boston, OH, 05433, USA
| | - Robert Markiewicz
- Northeastern University, Department of Physics, Boston, MA, 02115, USA
| | - Arun Bansil
- Northeastern University, Department of Physics, Boston, MA, 02115, USA
| | - Don Heiman
- Northeastern University, Department of Physics, Boston, MA, 02115, USA
- Plasma Science and Fusion Center, MIT, Cambridge, MA, 02139, USA
| | - Nian Xiang Sun
- Northeastern University, Department of Electrical and Computer Engineering, Boston, MA, 02115, USA
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8
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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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9
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Yao Y, Zhan X, Sendeku MG, Yu P, Dajan FT, Zhu C, Li N, Wang J, Wang F, Wang Z, He J. Recent progress on emergent two-dimensional magnets and heterostructures. NANOTECHNOLOGY 2021; 32:472001. [PMID: 34315143 DOI: 10.1088/1361-6528/ac17fd] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 07/26/2021] [Indexed: 06/13/2023]
Abstract
Intrinsic two-dimensional (2D) magnetic materials own strong long-range magnetism while their characteristics of the ultrathin thickness and smooth surface provide an ideal platform for manipulating the magnetic properties at 2D limit. This makes them to be potential candidates in various spintronic applications compared to their corresponding bulk counterparts. The discovery of magnetic ordering in 2D CrI3and Gr2Ge2Te6nanostructures stimulated tremendous research interest in both experimental and theoretical studies on various intrinsic magnets at 2D limit. This review gives a comprehensive overview of the recent progress on the emergent 2D magnets and heterostructures. Firstly, several kinds of typical 2D magnetic materials discovered in the last few years and their fabrication methods are summarized in detail. Secondly, the current strategies for manipulating magnetic properties in 2D materials are further discussed. Then, the recent advances on the construction of representative van der Waals magnetic heterostructures and their respective performance are provided. With the hope of motivating the researchers in this area, we finally offered the challenges and outlook on 2D magnetism.
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Affiliation(s)
- Yuyu Yao
- CAS Center for Excellence in Nanoscience, CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
- Sino-Danish College, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Sino-Danish Center for Education, Beijing 100049, People's Republic of China
| | - Xueying Zhan
- CAS Center for Excellence in Nanoscience, CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
| | - Marshet Getaye Sendeku
- CAS Center for Excellence in Nanoscience, CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
| | - Peng Yu
- CAS Center for Excellence in Nanoscience, CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
| | - Fekadu Tsegaye Dajan
- CAS Center for Excellence in Nanoscience, CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
| | - Chuanchao Zhu
- Institute for Quantum Information & State Key Laboratory of High Performance Computing, National University of Defense Technology, Changsha 410073, People's Republic of China
| | - Ningning Li
- CAS Center for Excellence in Nanoscience, CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
- Sino-Danish College, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Sino-Danish Center for Education, Beijing 100049, People's Republic of China
| | - Junjun Wang
- CAS Center for Excellence in Nanoscience, CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
| | - Feng Wang
- CAS Center for Excellence in Nanoscience, CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
| | - Zhenxing Wang
- CAS Center for Excellence in Nanoscience, CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Jun He
- CAS Center for Excellence in Nanoscience, CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072, People's Republic of China
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10
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Yang Q, Hu X, Shen X, Krasheninnikov AV, Chen Z, Sun L. Enhancing Ferromagnetism and Tuning Electronic Properties of CrI 3 Monolayers by Adsorption of Transition-Metal Atoms. ACS APPLIED MATERIALS & INTERFACES 2021; 13:21593-21601. [PMID: 33904708 DOI: 10.1021/acsami.1c01701] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Among first experimentally discovered two-dimensional (2D) ferromagnetic materials, chromium triiodide (CrI3) monolayers have attracted particular attention due to their potential applications in electronics and spintronics. However, the Curie temperature Tc of the CrI3 monolayer is below room temperature, which greatly limits practical development of the devices. Herein, using density functional theory calculation, we explore how the electronic and magnetic properties of CrI3 monolayers change upon adsorption of 3d transition-metal (TM) atoms (from Sc to Zn). Our results indicate that the electronic properties of the TM-CrI3 system can be tuned from semiconductor to metal/half-metal/spin gapless semiconductor depending on the choice of the adsorbed TM atoms. Moreover, the adsorption can improve the ferromagnetic stability of CrI3 monolayers by increasing both magnetic moments and Tc. Notably, Tc of CrI3 with Sc and V adatoms can be increased by nearly a factor of 3. We suggest postsynthesis doping of 2D CrI3 by deposition of TM atoms as a new route toward potential applications of TM-CrI3 systems in nanoelectronic and spintronic devices.
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Affiliation(s)
- Qiang Yang
- College of Materials Science and Engineering, Nanjing Tech University, Nanjing 211816, China
| | - Xiaohui Hu
- College of Materials Science and Engineering, Nanjing Tech University, Nanjing 211816, China
- Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites, Nanjing Tech University, Nanjing 211816, China
| | - Xiaodong Shen
- College of Materials Science and Engineering, Nanjing Tech University, Nanjing 211816, China
- Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites, Nanjing Tech University, Nanjing 211816, China
| | - Arkady V Krasheninnikov
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany
- Department of Applied Physics, Aalto University School of Science, P.O. Box 11100, 00076 Aalto, Finland
| | - Zhongfang Chen
- Department of Chemistry, University of Puerto Rico, Rio Piedras Campus, San Juan 00931, Puerto Rico
| | - Litao Sun
- SEU-FEI Nano-Pico Center, Key Laboratory of MEMS of Ministry of Education, Collaborative Innovation Center for Micro/Nano Fabrication, Device and System, Southeast University, Nanjing 210096, China
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11
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Ge J, Luo T, Lin Z, Shi J, Liu Y, Wang P, Zhang Y, Duan W, Wang J. Magnetic Moments Induced by Atomic Vacancies in Transition Metal Dichalcogenide Flakes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2005465. [PMID: 33306277 DOI: 10.1002/adma.202005465] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 11/19/2020] [Indexed: 06/12/2023]
Abstract
2D magnetism plays a key role in both fundamental physics and potential device applications. However, the instability of the discovered 2D magnetic materials has been one main obstacle in deep research and potential application of 2D magnetism. Here, a localized magnetic moment induced by Pt vacancies in air-stable type-II Dirac semimetal PtSe2 flakes is reported. The localized magnetic moments give rise to the Kondo effect, evidenced by logarithmic increment of resistance with decreasing temperature and isotropic negative longitudinal magnetoresistance. Additionally, the induced magnetic moment and Kondo temperature appear to depend on thickness in the thinner samples (<10 nm). The small magnetocrystalline anisotropy revealed by first-principles calculation indicates that the magnetic moments are randomly localized instead of long-range ordered. The findings demonstrate a new means to induce magnetism in 2D non-magnetic materials.
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Affiliation(s)
- Jun Ge
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
| | - Tianchuang Luo
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
| | - Zuzhang Lin
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
- Institute for Advanced Study, Tsinghua University, Beijing, 100084, China
| | - Jianping Shi
- The Institute for Advanced Studies, Wuhan University, Wuhan, 430072, China
| | - Yanzhao Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
| | - Pinyuan Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
| | - Yanfeng Zhang
- Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing, 100871, China
| | - Wenhui Duan
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
- Institute for Advanced Study, Tsinghua University, Beijing, 100084, China
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, 100190, China
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, China
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12
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Figueroa AI, Bonell F, Cuxart MG, Valvidares M, Gargiani P, van der Laan G, Mugarza A, Valenzuela SO. Absence of Magnetic Proximity Effect at the Interface of Bi_{2}Se_{3} and (Bi,Sb)_{2}Te_{3} with EuS. PHYSICAL REVIEW LETTERS 2020; 125:226801. [PMID: 33315425 DOI: 10.1103/physrevlett.125.226801] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 09/02/2020] [Accepted: 10/16/2020] [Indexed: 06/12/2023]
Abstract
We performed x-ray magnetic circular dichroism (XMCD) measurements on heterostructures comprising topological insulators (TIs) of the (Bi,Sb)_{2}(Se,Te)_{3} family and the magnetic insulator EuS. XMCD measurements allow us to investigate element-selective magnetic proximity effects at the very TI/EuS interface. A systematic analysis reveals that there is neither significant induced magnetism within the TI nor an enhancement of the Eu magnetic moment at such interface. The induced magnetic moments in Bi, Sb, Te, and Se sites are lower than the estimated detection limit of the XMCD measurements of ∼10^{-3} μ_{B}/at.
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Affiliation(s)
- A I Figueroa
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - F Bonell
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - M G Cuxart
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
- Universitat Autònoma de Barcelona (UAB), Bellaterra 08193, Spain
| | - M Valvidares
- ALBA Synchrotron Light Source, Barcelona 08290, Spain
| | - P Gargiani
- ALBA Synchrotron Light Source, Barcelona 08290, Spain
| | - G van der Laan
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - A Mugarza
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona 08010, Spain
| | - S O Valenzuela
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona 08010, Spain
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13
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Liu T, Kally J, Pillsbury T, Liu C, Chang H, Ding J, Cheng Y, Hilse M, Engel-Herbert R, Richardella A, Samarth N, Wu M. Changes of Magnetism in a Magnetic Insulator due to Proximity to a Topological Insulator. PHYSICAL REVIEW LETTERS 2020; 125:017204. [PMID: 32678653 DOI: 10.1103/physrevlett.125.017204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 04/13/2020] [Accepted: 06/05/2020] [Indexed: 06/11/2023]
Abstract
We report the modification of magnetism in a magnetic insulator Y_{3}Fe_{5}O_{12} thin film by topological surface states (TSS) in an adjacent topological insulator Bi_{2}Se_{3} thin film. Ferromagnetic resonance measurements show that the TSS in Bi_{2}Se_{3} produces a perpendicular magnetic anisotropy, results in a decrease in the gyromagnetic ratio, and enhances the damping in Y_{3}Fe_{5}O_{12}. Such TSS-induced changes become more pronounced as the temperature decreases from 300 to 50 K. These results suggest a completely new approach for control of magnetism in magnetic thin films.
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Affiliation(s)
- Tao Liu
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
| | - James Kally
- Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Timothy Pillsbury
- Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Chuanpu Liu
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Houchen Chang
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Jinjun Ding
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Yang Cheng
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Maria Hilse
- Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Roman Engel-Herbert
- Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Anthony Richardella
- Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Nitin Samarth
- Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Mingzhong Wu
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA
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14
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Zhong D, Seyler KL, Linpeng X, Wilson NP, Taniguchi T, Watanabe K, McGuire MA, Fu KMC, Xiao D, Yao W, Xu X. Layer-resolved magnetic proximity effect in van der Waals heterostructures. NATURE NANOTECHNOLOGY 2020; 15:187-191. [PMID: 31988503 DOI: 10.1038/s41565-019-0629-1] [Citation(s) in RCA: 78] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 12/18/2019] [Indexed: 06/10/2023]
Abstract
Magnetic proximity effects are integral to manipulating spintronic1,2, superconducting3,4, excitonic5 and topological phenomena6-8 in heterostructures. These effects are highly sensitive to the interfacial electronic properties, such as electron wavefunction overlap and band alignment. The recent emergence of magnetic two-dimensional materials opens new possibilities for exploring proximity effects in van der Waals heterostructures9-12. In particular, atomically thin CrI3 exhibits layered antiferromagnetism, in which adjacent ferromagnetic monolayers are antiferromagnetically coupled9. Here we report a layer-resolved magnetic proximity effect in heterostructures formed by monolayer WSe2 and bi/trilayer CrI3. By controlling the individual layer magnetization in CrI3 with a magnetic field, we show that the spin-dependent charge transfer between WSe2 and CrI3 is dominated by the interfacial CrI3 layer, while the proximity exchange field is highly sensitive to the layered magnetic structure as a whole. In combination with reflective magnetic circular dichroism measurements, these properties allow the use of monolayer WSe2 as a spatially sensitive magnetic sensor to map out layered antiferromagnetic domain structures at zero magnetic field as well as antiferromagnetic/ferromagnetic domains at finite magnetic fields. Our work reveals a way to control proximity effects and probe interfacial magnetic order via van der Waals engineering13.
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Affiliation(s)
- Ding Zhong
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Kyle L Seyler
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Xiayu Linpeng
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Nathan P Wilson
- Department of Physics, University of Washington, Seattle, WA, USA
| | | | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | - Michael A McGuire
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Kai-Mei C Fu
- Department of Physics, University of Washington, Seattle, WA, USA
- Department of Electrical and Computer Engineering, University of Washington, Seattle, WA, USA
| | - Di Xiao
- Department of Physics, Carnegie Mellon University, Pittsburg, PA, USA
| | - Wang Yao
- Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Hong Kong, China
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, USA.
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA.
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15
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Zeng Y, Wang L, Li S, He C, Zhong D, Yao DX. Topological phase transition induced by magnetic proximity effect in two dimensions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:395502. [PMID: 31185461 DOI: 10.1088/1361-648x/ab28d1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We study the magnetic proximity effect on a two-dimensional topological insulator in a CrI3/SnI3/CrI3 trilayer structure. From first-principles calculations, the BiI3-type SnI3 monolayer without spin-orbit coupling has Dirac cones at the corners of the hexagonal Brillouin zone. With spin-orbit coupling turned on, it becomes a topological insulator, as revealed by a non-vanishing Z 2 invariant and an effective model from symmetry considerations. Without spin-orbit coupling, the Dirac points are protected if the CrI3 layers are stacked ferromagnetically, and are gapped if the CrI3 layers are stacked antiferromagnetically, which can be explained by the irreducible representations of the magnetic space groups [Formula: see text] and [Formula: see text], corresponding to ferromagnetic and antiferromagnetic stacking, respectively. By analyzing the effective model including the perturbations, we find that the competition between the magnetic proximity effect and spin-orbit coupling leads to a topological phase transition between a trivial insulator and a topological insulator.
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Affiliation(s)
- Yijie Zeng
- 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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16
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Li H, Ruan S, Zeng YJ. Intrinsic Van Der Waals Magnetic Materials from Bulk to the 2D Limit: New Frontiers of Spintronics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1900065. [PMID: 31069896 DOI: 10.1002/adma.201900065] [Citation(s) in RCA: 106] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 02/21/2019] [Indexed: 05/22/2023]
Abstract
2D van der Waals (vdW) magnets, which present intrinsic ferromagnetic/antiferromagnetic ground states at finite temperatures down to atomic-layer thicknesses, open a new horizon in materials science and enable the potential development of new spin-related applications. The layered structure of vdW magnets facilitates their atomic-layer cleavability and magnetic anisotropy, which counteracts spin fluctuations, thereby providing an ideal platform for theoretically and experimentally exploring magnetic phase transitions in the 2D limit. With reduced dimensions, the susceptibility of 2D magnets to a large variety of external stimuli also makes them more promising than their bulk counterpart in various device applications. Here, the current status of characterization and tuning of the magnetic properties of 2D vdW magnets, particularly the atomic-layer thickness, is presented. Various state-of-the-art optical and electrical techniques have been applied to reveal the magnetic states of 2D vdW magnets. Other emerging 2D vdW magnets and future perspectives on the stacking strategy are also given; it is believed that they will excite more intensive research and provide unprecedented opportunities in the field of spintronics.
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Affiliation(s)
- Hui Li
- College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
- Center for Advanced Material Diagnostic Technology, Shenzhen Technology University, Shenzhen, 518118, P. R. China
| | - Shuangchen Ruan
- College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
| | - Yu-Jia Zeng
- College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
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17
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Ge M, Su Y, Wang H, Yang G, Zhang J. Interface depended electronic and magnetic properties of vertical CrI3/WSe2 heterostructures. RSC Adv 2019; 9:14766-14771. [PMID: 35516340 PMCID: PMC9064251 DOI: 10.1039/c9ra01825e] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 05/07/2019] [Indexed: 11/21/2022] Open
Abstract
Owing to the great potential applications in information processing and storage, two-dimensional (2D) magnetic materials have recently attracted significant attention. Here, using first-principles calculations, we investigate the electronic and magnetic properties of the van der Waals CrI3/WSe2 heterostructures. We find that after forming heterostructures, monolayer CrI3 undergoes a direct to indirect band gap transition and its gap size is greatly reduced. In particular, the out-plane spin quantization axis of monolayer CrI3 is tuned into in-plane for most stacking configurations of CrI3/WSe2. We further reveal that the transition of the easy magnetization direction is mainly originated from the hybridization between Cr-d and Se-p orbitals. These theoretical results provide a useful picture for the electronic structure and magnetic anisotropy behaviors in vertical CrI3/WSe2 heterostructures. The out-plane easy axis is tuned into in-plane in both CrI3/WSe2 and WSe2/CrI3/WSe2 vertical heterostructures.![]()
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Affiliation(s)
- Mei Ge
- School of Physics and Information Engineering
- Shanxi Normal University
- Linfen
- China
- Key Laboratory of Spectral Measurement and Analysis of Shanxi Province
| | - Yan Su
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams
- Dalian University of Technology
- Ministry of Education
- Dalian 116024
- China
| | - Han Wang
- Chemical Sciences Division
- Lawrence Berkeley National Laboratory
- Berkeley
- USA
| | - Guohui Yang
- Key Laboratory of Spectral Measurement and Analysis of Shanxi Province
- Shanxi Normal University
- Linfen
- China
| | - Junfeng Zhang
- Key Laboratory of Spectral Measurement and Analysis of Shanxi Province
- Shanxi Normal University
- Linfen
- China
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18
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Zhang K, Zeng J, Dong X, Cheng Q. Spin dependence of crossed Andreev reflection and electron tunneling induced by Majorana fermions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:505302. [PMID: 30474619 DOI: 10.1088/1361-648x/aaedf6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We investigate spin dependence of the nonlocal transport induced by Majorana fermions in a one-dimensional ferromagnet-ferromagnetic-insulator-superconductor-ferromagnetic-insulator-ferromagnet junction on the edge of a two-dimensional topological insulator. The results show that coupled Majorana fermions lead to the nonlocal transport processes including electron tunneling and crossed Andreev reflection, which can be tuned by adjusting the spin polarizations of the Majorana fermions. By manipulating the bands in the two ferromagnets, the nonlocal transport can be selected as either pure electron tunneling or pure crossed Andreev reflection, the transmission probability of which could be 100%. Furthermore, the pure electron tunneling and the pure crossed Andreev reflection are well controlled by the spin directions of the electron states in the two ferromagnets.
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Affiliation(s)
- Kunhua Zhang
- ICQD, Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
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19
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Eremeev SV, Otrokov MM, Chulkov EV. New Universal Type of Interface in the Magnetic Insulator/Topological Insulator Heterostructures. NANO LETTERS 2018; 18:6521-6529. [PMID: 30260648 DOI: 10.1021/acs.nanolett.8b03057] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Magnetic proximity effect at the interface between magnetic and topological insulators (MIs and TIs) is considered to have great potential in spintronics as, in principle, it allows realizing the quantum anomalous Hall and topological magneto-electric effects (QAHE and TME). Although an out-of-plane magnetization induced in a TI by the proximity effect was successfully probed in experiments, first-principles calculations reveal that a strong electrostatic potential mismatch at abrupt MI/TI interfaces creates harmful trivial states rendering both the QAHE and TME unfeasible in practice. Here on the basis of recent progress in formation of planar self-assembled single layer MI/TI heterostructure (T. Hirahara et al. Nano Lett. 2017 , 17 , 3493 - 3500 ), we propose a conceptually new type of the MI/TI interfaces by means of density functional theory calculations. By considering MnSe/Bi2Se3, MnTe/Bi2Te3, and EuS/Bi2Se3 we demonstrate that, instead of a sharp MI/TI interface clearly separating the two subsystems, it is energetically far more favorable to form a built-in interface via insertion of the MI film inside the TI's surface quintuple layer (e.g., Se-Bi-Se-[MnSe]-Bi-Se) where it forms a bulk-like MI structure. This results in a smooth MI-to-TI connection that yields the interface electronic structure essentially free of trivial states. Our findings open a new direction in studies of the MI/TI interfaces and restore their potential for the QAHE and TME observation.
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Affiliation(s)
- Sergey V Eremeev
- Institute of Strength Physics and Materials Science , Tomsk 634055 , Russia
- Tomsk State University , Tomsk 634050 , Russia
- Saint Petersburg State University , Saint Petersburg 198504 , Russia
- Donostia International Physics Center (DIPC) , Paseo de Manuel Lardizabal, 4 , 20018 San Sebastián/Donostia , Basque Country , Spain
| | - Mikhail M Otrokov
- Tomsk State University , Tomsk 634050 , Russia
- Saint Petersburg State University , Saint Petersburg 198504 , Russia
- Departamento de Física de Materiales UPV/EHU , Centro de Física de Materiales CFM - MPC and Centro Mixto CSIC-UPV/EHU , 20080 San Sebastián/Donostia , Spain
- IKERBASQUE , Basque Foundation for Science , 48011 Bilbao , Spain
| | - Evgueni V Chulkov
- Tomsk State University , Tomsk 634050 , Russia
- Saint Petersburg State University , Saint Petersburg 198504 , Russia
- Donostia International Physics Center (DIPC) , Paseo de Manuel Lardizabal, 4 , 20018 San Sebastián/Donostia , Basque Country , Spain
- Departamento de Física de Materiales UPV/EHU , Centro de Física de Materiales CFM - MPC and Centro Mixto CSIC-UPV/EHU , 20080 San Sebastián/Donostia , Spain
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20
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Averyanov DV, Parfenov OE, Tokmachev AM, Karateev IA, Kondratev OA, Taldenkov AN, Platunov MS, Wilhelm F, Rogalev A, Storchak VG. Fine structure of metal-insulator transition in EuO resolved by doping engineering. NANOTECHNOLOGY 2018; 29:195706. [PMID: 29469062 DOI: 10.1088/1361-6528/aab16e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Metal-insulator transitions (MITs) offer new functionalities for nanoelectronics. However, ongoing attempts to control the resistivity by external stimuli are hindered by strong coupling of spin, charge, orbital and lattice degrees of freedom. This difficulty presents a quest for materials which exhibit MIT caused by a single degree of freedom. In the archetypal ferromagnetic semiconductor EuO, magnetic orders dominate the MIT. Here we report a new approach to take doping under control in this material on the nanoscale: formation of oxygen vacancies is strongly suppressed to exhibit the highest MIT resistivity jump and magnetoresistance among thin films. The nature of the MIT is revealed in Gd doped films. The critical doping is determined to be more than an order of magnitude lower than in all previous studies. In lightly doped films, a remarkable thermal hysteresis in resistivity is discovered. It extends over 100 K in the paramagnetic phase reaching 3 orders of magnitude. In the warming mode, the MIT is shown to be a two-step process. The resistivity patterns are consistent with an active role of magnetic polarons-formation of a narrow band and its thermal destruction. High-temperature magnetic polaron effects include large negative magnetoresistance and ferromagnetic droplets revealed by x-ray magnetic circular dichroism. Our findings have wide-range implications for the understanding of strongly correlated oxides and establish fundamental benchmarks to guide theoretical models of the MIT.
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Affiliation(s)
- Dmitry V Averyanov
- National Research Center 'Kurchatov Institute', Kurchatov Sq. 1, Moscow 123182, Russia
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21
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In C, Sim S, Kim B, Bae H, Jung H, Jang W, Son M, Moon J, Salehi M, Seo SY, Soon A, Ham MH, Lee H, Oh S, Kim D, Jo MH, Choi H. Control over Electron-Phonon Interaction by Dirac Plasmon Engineering in the Bi 2Se 3 Topological Insulator. NANO LETTERS 2018; 18:734-739. [PMID: 29347815 DOI: 10.1021/acs.nanolett.7b03897] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Understanding the mutual interaction between electronic excitations and lattice vibrations is key for understanding electronic transport and optoelectronic phenomena. Dynamic manipulation of such interaction is elusive because it requires varying the material composition on the atomic level. In turn, recent studies on topological insulators (TIs) have revealed the coexistence of a strong phonon resonance and topologically protected Dirac plasmon, both in the terahertz (THz) frequency range. Here, using these intrinsic characteristics of TIs, we demonstrate a new methodology for controlling electron-phonon interaction by lithographically engineered Dirac surface plasmons in the Bi2Se3 TI. Through a series of time-domain and time-resolved ultrafast THz measurements, we show that, when the Dirac plasmon energy is less than the TI phonon energy, the electron-phonon coupling is trivial, exhibiting phonon broadening associated with Landau damping. In contrast, when the Dirac plasmon energy exceeds that of the phonon resonance, we observe suppressed electron-phonon interaction leading to unexpected phonon stiffening. Time-dependent analysis of the Dirac plasmon behavior, phonon broadening, and phonon stiffening reveals a transition between the distinct dynamics corresponding to the two regimes as the Dirac plasmon resonance moves across the TI phonon resonance, which demonstrates the capability of Dirac plasmon control. Our results suggest that the engineering of Dirac plasmons provides a new alternative for controlling the dynamic interaction between Dirac carriers and phonons.
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Affiliation(s)
| | - Sangwan Sim
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS) , Pohang 37673, Republic of Korea
| | | | | | - Hyunseung Jung
- School of Electronic Engineering, Soongsil University , Seoul 06978, Republic of Korea
| | | | - Myungwoo Son
- School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST) , Gwangju 61005, Republic of Korea
| | | | | | | | | | - Moon-Ho Ham
- School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST) , Gwangju 61005, Republic of Korea
| | - Hojin Lee
- School of Electronic Engineering, Soongsil University , Seoul 06978, Republic of Korea
| | | | - Dohun Kim
- Department of Physics and Astronomy, Seoul National University , Seoul 08826, Republic of Korea
| | - Moon-Ho Jo
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS) , Pohang 37673, Republic of Korea
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22
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Zhang S, Kronast F, van der Laan G, Hesjedal T. Real-Space Observation of Skyrmionium in a Ferromagnet-Magnetic Topological Insulator Heterostructure. NANO LETTERS 2018; 18:1057-1063. [PMID: 29363315 DOI: 10.1021/acs.nanolett.7b04537] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The combination of topological insulators, that is, bulk insulators with gapless, topologically protected surface states, with magnetic order is a love-hate relationship that can unlock new quantum states and exotic physical phenomena, such as the quantum anomalous Hall effect and axion electrodynamics. Moreover, the unusual coupling between topological insulators and ferromagnets can also result in the formation of topological spin textures in the ferromagnetic layer. Skyrmions are topologically protected magnetization swirls that are promising candidates for spintronics memory carriers. Here, we report on the observation of skyrmionium in thin ferromagnetic films coupled to a magnetic topological insulator. The occurrence of skyrmionium, which appears as a soliton composed of two skyrmions with opposite winding numbers, is tied to the ferromagnetic state of the topological insulator. Our work presents a new combination of two important classes of topological materials and may open the door to new topologically inspired information-storage concepts in the future.
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Affiliation(s)
- Shilei Zhang
- Clarendon Laboratory, Department of Physics, University of Oxford , Parks Road, Oxford, OX1 3PU, United Kingdom
| | - Florian Kronast
- Helmholtz-Zentrum Berlin für Materialien und Energie , Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - Gerrit van der Laan
- Magnetic Spectroscopy Group , Diamond Light Source, Didcot, OX11 0DE, United Kingdom
| | - Thorsten Hesjedal
- Clarendon Laboratory, Department of Physics, University of Oxford , Parks Road, Oxford, OX1 3PU, United Kingdom
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23
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Breunig D, Burset P, Trauzettel B. Creation of Spin-Triplet Cooper Pairs in the Absence of Magnetic Ordering. PHYSICAL REVIEW LETTERS 2018; 120:037701. [PMID: 29400487 DOI: 10.1103/physrevlett.120.037701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 12/20/2017] [Indexed: 06/07/2023]
Abstract
In superconducting spintronics, it is essential to generate spin-triplet Cooper pairs on demand. Up to now, proposals to do so concentrate on hybrid structures in which a superconductor (SC) is combined with a magnetically ordered material (or an external magnetic field). We, instead, identify a novel way to create and isolate spin-triplet Cooper pairs in the absence of any magnetic ordering. This achievement is only possible because we drive a system with strong spin-orbit interaction-the Dirac surface states of a strong topological insulator (TI)-out of equilibrium. In particular, we consider a bipolar TI-SC-TI junction, where the electrochemical potentials in the outer leads differ in their overall sign. As a result, we find that nonlocal singlet pairing across the junction is completely suppressed for any excitation energy. Hence, this junction acts as a perfect spin-triplet filter across the SC, generating equal-spin Cooper pairs via crossed Andreev reflection.
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Affiliation(s)
- Daniel Breunig
- Institute for Theoretical Physics and Astrophysics, University of Würzburg, 97074 Würzburg, Germany
| | - Pablo Burset
- Department of Applied Physics, Aalto University, 00076 Aalto, Finland
| | - Björn Trauzettel
- Institute for Theoretical Physics and Astrophysics, University of Würzburg, 97074 Würzburg, Germany
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24
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Fanchiang YT, Chen KHM, Tseng CC, Chen CC, Cheng CK, Yang SR, Wu CN, Lee SF, Hong M, Kwo J. Strongly exchange-coupled and surface-state-modulated magnetization dynamics in Bi 2Se 3/yttrium iron garnet heterostructures. Nat Commun 2018; 9:223. [PMID: 29335558 PMCID: PMC5768741 DOI: 10.1038/s41467-017-02743-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2017] [Accepted: 12/20/2017] [Indexed: 12/03/2022] Open
Abstract
Harnessing the spin–momentum locking of topological surface states in conjunction with magnetic materials is the first step to realize novel topological insulator-based devices. Here, we report strong interfacial coupling in Bi2Se3/yttrium iron garnet (YIG) bilayers manifested as large interfacial in-plane magnetic anisotropy (IMA) and enhancement of damping probed by ferromagnetic resonance. The interfacial IMA and damping enhancement reaches a maximum when the Bi2Se3 film approaches its two-dimensional limit, indicating that topological surface states play an important role in the magnetization dynamics of YIG. Temperature-dependent ferromagnetic resonance of Bi2Se3/YIG reveals signatures of the magnetic proximity effect of TC as high as 180 K, an emerging low-temperature perpendicular magnetic anisotropy competing the high-temperature IMA, and an increasing exchange effective field of YIG steadily increasing toward low temperature. Our study sheds light on the effects of topological insulators on magnetization dynamics, essential for the development of topological insulator-based spintronic devices. Understanding the effects of topological insulators on magnetization dynamics of adjacent magnetic materials is essential for novel spintronic devices. Here, Fanchiang et al. report thickness dependence of interfacial in-plane magnetic anisotropy and damping enhancement in Bi2Se3/yttrium iron garnet (YIG) bilayers, indicating an important role of topological surface states in the magnetization dynamics of YIG.
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Affiliation(s)
- Y T Fanchiang
- Department of Physics, National Taiwan University, Taipei, 10617, Taiwan
| | - K H M Chen
- Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - C C Tseng
- Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - C C Chen
- Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - C K Cheng
- Department of Physics, National Taiwan University, Taipei, 10617, Taiwan
| | - S R Yang
- Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - C N Wu
- Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - S F Lee
- Institute of Physics, Academia Sinica, Taipei, 11529, Taiwan.
| | - M Hong
- Department of Physics, National Taiwan University, Taipei, 10617, Taiwan.
| | - J Kwo
- Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan.
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25
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Tang C, Chang CZ, Zhao G, Liu Y, Jiang Z, Liu CX, McCartney MR, Smith DJ, Chen T, Moodera JS, Shi J. Above 400-K robust perpendicular ferromagnetic phase in a topological insulator. SCIENCE ADVANCES 2017; 3:e1700307. [PMID: 28691097 PMCID: PMC5482549 DOI: 10.1126/sciadv.1700307] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 04/21/2017] [Indexed: 05/23/2023]
Abstract
The quantum anomalous Hall effect (QAHE) that emerges under broken time-reversal symmetry in topological insulators (TIs) exhibits many fascinating physical properties for potential applications in nanoelectronics and spintronics. However, in transition metal-doped TIs, the only experimentally demonstrated QAHE system to date, the QAHE is lost at practically relevant temperatures. This constraint is imposed by the relatively low Curie temperature (Tc) and inherent spin disorder associated with the random magnetic dopants. We demonstrate drastically enhanced Tc by exchange coupling TIs to Tm3Fe5O12, a high-Tc magnetic insulator with perpendicular magnetic anisotropy. Signatures showing that the TI surface states acquire robust ferromagnetism are revealed by distinct squared anomalous Hall hysteresis loops at 400 K. Point-contact Andreev reflection spectroscopy confirms that the TI surface is spin-polarized. The greatly enhanced Tc, absence of spin disorder, and perpendicular anisotropy are all essential to the occurrence of the QAHE at high temperatures.
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Affiliation(s)
- Chi Tang
- Department of Physics and Astronomy, University of California, Riverside, Riverside, CA 92521, USA
| | - Cui-Zu Chang
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | - Gejian Zhao
- Department of Physics, Arizona State University, Tempe, AZ 85287, USA
| | - Yawen Liu
- Department of Physics and Astronomy, University of California, Riverside, Riverside, CA 92521, USA
| | - Zilong Jiang
- Department of Physics and Astronomy, University of California, Riverside, Riverside, CA 92521, USA
| | - Chao-Xing Liu
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | | | - David J. Smith
- Department of Physics, Arizona State University, Tempe, AZ 85287, USA
| | - Tingyong Chen
- Department of Physics, Arizona State University, Tempe, AZ 85287, USA
| | - Jagadeesh S. Moodera
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jing Shi
- Department of Physics and Astronomy, University of California, Riverside, Riverside, CA 92521, USA
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26
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Jeon JH, Kim H, Jang WJ, Seo J, Kahng SJ. Thickness-dependent Dirac dispersions of few-layer topological insulators supported by metal substrate. NANOTECHNOLOGY 2017; 28:215207. [PMID: 28474604 DOI: 10.1088/1361-6528/aa6b52] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The surface states protected by time-reversal symmetry in 3-dimensional topological insulators have recently been confirmed by angle-resolved photoemission spectroscopy, scanning tunneling microscopy, quantum transport and so on. However, the electronic properties of ultra-thin topological insulator films have not been extensively studied, especially when the films are grown on metal substrates. In this paper, we have elucidated the local behaviors of the electronic states of ultra-thin topological insulator Bi2Se3 grown with molecular beam epitaxy on Au(111) using scanning tunneling microscopy/spectroscopy. We have observed linear dispersion of electron interference patterns at higher energies than the Fermi energy that were not accessible by conventional angle-resolved photoemission spectroscopy. Moreover, the dispersion of the interference patterns varies with the film thickness, which is explained by band bending near the interface between the topological insulator and the metal substrate. Our experiments demonstrate that interfacial effects in thin topological insulator films on metal substrate can be sensed using scanning tunneling spectroscopy.
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Affiliation(s)
- Jeong Heum Jeon
- Department of Physics, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea
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27
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Zhong D, Seyler KL, Linpeng X, Cheng R, Sivadas N, Huang B, Schmidgall E, Taniguchi T, Watanabe K, McGuire MA, Yao W, Xiao D, Fu KMC, Xu X. Van der Waals engineering of ferromagnetic semiconductor heterostructures for spin and valleytronics. SCIENCE ADVANCES 2017; 3:e1603113. [PMID: 28580423 PMCID: PMC5451195 DOI: 10.1126/sciadv.1603113] [Citation(s) in RCA: 255] [Impact Index Per Article: 36.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 04/03/2017] [Indexed: 05/22/2023]
Abstract
The integration of magnetic material with semiconductors has been fertile ground for fundamental science as well as of great practical interest toward the seamless integration of information processing and storage. We create van der Waals heterostructures formed by an ultrathin ferromagnetic semiconductor CrI3 and a monolayer of WSe2. We observe unprecedented control of the spin and valley pseudospin in WSe2, where we detect a large magnetic exchange field of nearly 13 T and rapid switching of the WSe2 valley splitting and polarization via flipping of the CrI3 magnetization. The WSe2 photoluminescence intensity strongly depends on the relative alignment between photoexcited spins in WSe2 and the CrI3 magnetization, because of ultrafast spin-dependent charge hopping across the heterostructure interface. The photoluminescence detection of valley pseudospin provides a simple and sensitive method to probe the intriguing domain dynamics in the ultrathin magnet, as well as the rich spin interactions within the heterostructure.
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Affiliation(s)
- Ding Zhong
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | - Kyle L. Seyler
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | - Xiayu Linpeng
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | - Ran Cheng
- Department of Physics, Carnegie Mellon University, Pittsburg, PA 15213, USA
| | - Nikhil Sivadas
- Department of Physics, Carnegie Mellon University, Pittsburg, PA 15213, USA
| | - Bevin Huang
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | - Emma Schmidgall
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Michael A. McGuire
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Wang Yao
- Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Hong Kong, China
| | - Di Xiao
- Department of Physics, Carnegie Mellon University, Pittsburg, PA 15213, USA
| | - Kai-Mei C. Fu
- Department of Physics, University of Washington, Seattle, WA 98195, USA
- Department of Electrical Engineering, University of Washington, Seattle, WA 98195, USA
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA 98195, USA
- Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA
- Corresponding author.
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