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Li Q, Mo SK, Edmonds MT. Recent progress of MnBi 2Te 4 epitaxial thin films as a platform for realising the quantum anomalous Hall effect. NANOSCALE 2024. [PMID: 39015951 DOI: 10.1039/d4nr00194j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/18/2024]
Abstract
Since the first realisation of the quantum anomalous Hall effect (QAHE) in a dilute magnetic-doped topological insulator thin film in 2013, the quantisation temperature has been limited to less than 1 K due to magnetic disorder in dilute magnetic systems. With magnetic moments ordered into the crystal lattice, the intrinsic magnetic topological insulator MnBi2Te4 has the potential to eliminate or significantly reduce magnetic disorder and improve the quantisation temperature. Surprisingly, to date, the QAHE has yet to be observed in molecular beam epitaxy (MBE)-grown MnBi2Te4 thin films at zero magnetic field, and what leads to the difficulty in quantisation is still an active research area. Although bulk MnBi2Te4 and exfoliated flakes have been well studied, revealing both the QAHE and axion insulator phases, experimental progress on MBE thin films has been slower. Understanding how the breakdown of the QAHE occurs in MnBi2Te4 thin films and finding solutions that will enable mass-produced millimetre-size QAHE devices operating at elevated temperatures are required. In this mini-review, we will summarise recent studies on the electronic and magnetic properties of MBE MnBi2Te4 thin films and discuss mechanisms that could explain the failure of the QAHE from the aspects of defects, electronic structure, magnetic order, and consequences of their delicate interplay. Finally, we propose several strategies for realising the QAHE at elevated temperatures in MnBi2Te4 thin films.
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Affiliation(s)
- Qile Li
- School of Physics and Astronomy, Monash University, Clayton, VIC, Australia.
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, VIC, Australia
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Mark T Edmonds
- School of Physics and Astronomy, Monash University, Clayton, VIC, Australia.
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, VIC, Australia
- ANFF-VIC Technology Fellow, Melbourne Centre for Nanofabrication, Victorian Node of the Australian National Fabrication Facility, Clayton, VIC 3168, Australia
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Xu R, Xu L, Liu Z, Yang L, Chen Y. ARPES investigation of the electronic structure and its evolution in magnetic topological insulator MnBi 2+2nTe 4+3n family. Natl Sci Rev 2024; 11:nwad313. [PMID: 38327664 PMCID: PMC10849349 DOI: 10.1093/nsr/nwad313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 11/14/2023] [Accepted: 11/19/2023] [Indexed: 02/09/2024] Open
Abstract
In the past 5 years, there has been significant research interest in the intrinsic magnetic topological insulator family compounds MnBi2+2nTe4+3n (where n = 0, 1, 2 …). In particular, exfoliated thin films of MnBi2Te4 have led to numerous experimental breakthroughs, such as the quantum anomalous Hall effect, axion insulator phase and high-Chern number quantum Hall effect without Landau levels. However, despite extensive efforts, the energy gap of the topological surface states due to exchange magnetic coupling, which is a key feature of the characteristic band structure of the system, remains experimentally elusive. The electronic structure measured by using angle-resolved photoemission (ARPES) shows significant deviation from ab initio prediction and scanning tunneling spectroscopy measurements, making it challenging to understand the transport results based on the electronic structure. This paper reviews the measurements of the band structure of MnBi2+2nTe4+3n magnetic topological insulators using ARPES, focusing on the evolution of their electronic structures with temperature, surface and bulk doping and film thickness. The aim of the review is to construct a unified picture of the electronic structure of MnBi2+2nTe4+3n compounds and explore possible control of their topological properties.
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Affiliation(s)
- Runzhe Xu
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Lixuan Xu
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai 201210, China
| | - Zhongkai Liu
- School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai 201210, China
- ShanghaiTech Laboratory for Topological Physics, Shanghai 200031, China
| | - Lexian Yang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
| | - Yulin Chen
- School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai 201210, China
- ShanghaiTech Laboratory for Topological Physics, Shanghai 200031, China
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK
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Gultom P, Hsu CC, Lee MK, Su SH, Huang JCA. Epitaxial Growth and Characterization of Nanoscale Magnetic Topological Insulators: Cr-Doped (Bi 0.4Sb 0.6) 2Te 3. NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:157. [PMID: 38251122 PMCID: PMC10821443 DOI: 10.3390/nano14020157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 12/30/2023] [Accepted: 01/07/2024] [Indexed: 01/23/2024]
Abstract
The exploration initiated by the discovery of the topological insulator (BixSb1-x)2Te3 has extended to unlock the potential of quantum anomalous Hall effects (QAHEs), marking a revolutionary era for topological quantum devices, low-power electronics, and spintronic applications. In this study, we present the epitaxial growth of Cr-doped (Bi0.4Sb0.6)2Te3 (Cr:BST) thin films via molecular beam epitaxy, incorporating various Cr doping concentrations with varying Cr/Sb ratios (0.025, 0.05, 0.075, and 0.1). High-quality crystalline of the Cr:BST thin films deposited on a c-plane sapphire substrate has been rigorously confirmed through reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM) analyses. The existence of a Cr dopant has been identified with a reduction in the lattice parameter of BST from 30.53 ± 0.05 to 30.06 ± 0.04 Å confirmed by X-ray diffraction, and the valence state of Cr verified by X-ray photoemission (XPS) at binding energies of ~573.1 and ~583.5 eV. Additionally, the influence of Cr doping on lattice vibration was qualitatively examined by Raman spectroscopy, revealing a blue shift in peaks with increased Cr concentration. Surface characteristics, crucial for the functionality of topological insulators, were explored via Atomic Force Microscopy (AFM), illustrating a sevenfold reduction in surface roughness as the Cr concentration increased from 0 to 0.1. The ferromagnetic properties of Cr:BST were examined by a superconducting quantum interference device (SQUID) with a magnetic field applied in out-of-plane and in-plane directions. The Cr:BST samples exhibited a Curie temperature (Tc) above 50 K, accompanied by increased magnetization and coercivity with increasing Cr doping levels. The introduction of the Cr dopant induces a transition from n-type ((Bi0.4Sb0.6)2Te3) to p-type (Cr:(Bi0.4Sb0.6)2Te3) carriers, demonstrating a remarkable suppression of carrier density up to one order of magnitude, concurrently enhancing carrier mobility up to a factor of 5. This pivotal outcome is poised to significantly influence the development of QAHE studies and spintronic applications.
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Affiliation(s)
- Pangihutan Gultom
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan; (P.G.); (C.-C.H.)
| | - Chia-Chieh Hsu
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan; (P.G.); (C.-C.H.)
| | - Min Kai Lee
- Instrument Division, Core Facility Center, National Cheng Kung University, Tainan 701, Taiwan;
| | - Shu Hsuan Su
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan; (P.G.); (C.-C.H.)
| | - Jung-Chung-Andrew Huang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan; (P.G.); (C.-C.H.)
- Instrument Division, Core Facility Center, National Cheng Kung University, Tainan 701, Taiwan;
- Department of Applied Physics, National Kaohsiung University, Kaohsiung 811, Taiwan
- Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 10601, Taiwan
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Andersen MP, Mikheev E, Rosen IT, Tai L, Zhang P, Wang KL, Kastner MA, Goldhaber-Gordon D. Universal Conductance Fluctuations in a MnBi 2Te 4 Thin Film. NANO LETTERS 2023. [PMID: 38029283 DOI: 10.1021/acs.nanolett.3c02932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2023]
Abstract
Quantum coherence of electrons can produce striking behaviors in mesoscopic conductors. Although magnetic order can also strongly affect transport, the combination of coherence and magnetic order has been largely unexplored. Here, we examine quantum coherence-driven universal conductance fluctuations in the antiferromagnetic, canted antiferromagnetic, and ferromagnetic phases of a thin film of the topological material MnBi2Te4. In each magnetic phase, we extract a charge carrier phase coherence length of about 100 nm. The conductance magnetofingerprint is repeatable when sweeping applied magnetic field within one magnetic phase. Surprisingly, in the antiferromagnetic and canted antiferromagnetic phases, but not in the ferromagnetic phase, the magnetofingerprint depends on the direction of the field sweep. To explain our observations, we suggest that conductance fluctuation measurements are sensitive to the motion and nucleation of magnetic domain walls in MnBi2Te4.
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Affiliation(s)
- Molly P Andersen
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
- Department of Physics, University of Cincinnati, Cincinnati, Ohio 45221, United States
| | - Evgeny Mikheev
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
- Department of Physics, Stanford University, Stanford, California 94305, United States
- Department of Physics, University of Cincinnati, Cincinnati, Ohio 45221, United States
| | - Ilan T Rosen
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
- Department of Physics, University of Cincinnati, Cincinnati, Ohio 45221, United States
- Department of Applied Physics, Stanford University, Stanford, California 94305, United States
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Lixuan Tai
- Department of Electrical and Computer Engineering, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Peng Zhang
- Department of Electrical and Computer Engineering, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Kang L Wang
- Department of Electrical and Computer Engineering, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Marc A Kastner
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
- Department of Physics, Stanford University, Stanford, California 94305, United States
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - David Goldhaber-Gordon
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
- Department of Physics, Stanford University, Stanford, California 94305, United States
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Blank TGH, Grishunin KA, Zvezdin KA, Hai NT, Wu JC, Su SH, Huang JCA, Zvezdin AK, Kimel AV. Two-Dimensional Terahertz Spectroscopy of Nonlinear Phononics in the Topological Insulator MnBi_{2}Te_{4}. PHYSICAL REVIEW LETTERS 2023; 131:026902. [PMID: 37505956 DOI: 10.1103/physrevlett.131.026902] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2023] [Revised: 03/08/2023] [Accepted: 06/05/2023] [Indexed: 07/30/2023]
Abstract
The interaction of a single-cycle terahertz electric field with the topological insulator MnBi_{2}Te_{4} triggers strongly anharmonic lattice dynamics, promoting fully coherent energy transfer between the otherwise noninteracting Raman-active E_{g} and infrared (IR)-active E_{u} phononic modes. Two-dimensional terahertz spectroscopy combined with modeling based on the classical equations of motion and symmetry analysis reveals the multistage process underlying the excitation of the Raman-active E_{g} phonon. In this nonlinear combined photophononic process, the terahertz electric field first prepares a coherent IR-active E_{u} phononic state and subsequently interacts with this state to efficiently excite the E_{g} phonon.
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Affiliation(s)
- T G H Blank
- Institute for Molecules and Materials, Radboud University, 6525 AJ Nijmegen, Netherlands
| | - K A Grishunin
- Institute for Molecules and Materials, Radboud University, 6525 AJ Nijmegen, Netherlands
| | - K A Zvezdin
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia
- HSE University, 101000 Moscow, Russia
| | - N T Hai
- Department of Physics, National Changhua University of Education, Changhua 500, Taiwan
| | - J C Wu
- Department of Physics, National Changhua University of Education, Changhua 500, Taiwan
| | - S-H Su
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - J-C A Huang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - A K Zvezdin
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia
- New Spintonic Technologies LLC, 121205 Moscow, Russia
| | - A V Kimel
- Institute for Molecules and Materials, Radboud University, 6525 AJ Nijmegen, Netherlands
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Vyazovskaya AY, Petrov EK, Koroteev YM, Bosnar M, Silkin IV, Chulkov EV, Otrokov MM. Superlattices of Gadolinium and Bismuth Based Thallium Dichalcogenides as Potential Magnetic Topological Insulators. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 13:38. [PMID: 36615948 PMCID: PMC9824305 DOI: 10.3390/nano13010038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 12/17/2022] [Accepted: 12/17/2022] [Indexed: 06/17/2023]
Abstract
Using relativistic spin-polarized density functional theory calculations we investigate magnetism, electronic structure and topology of the ternary thallium gadolinium dichalcogenides TlGdZ2 (Z= Se and Te) as well as superlattices on their basis. We find TlGdZ2 to have an antiferromagnetic exchange coupling both within and between the Gd layers, which leads to frustration and a complex magnetic structure. The electronic structure calculations reveal both TlGdSe2 and TlGdTe2 to be topologically trivial semiconductors. However, as we show further, a three-dimensional (3D) magnetic topological insulator (TI) state can potentially be achieved by constructing superlattices of the TlGdZ2/(TlBiZ2)n type, in which structural units of TlGdZ2 are alternated with those of the isomorphic TlBiZ2 compounds, known to be non-magnetic 3D TIs. Our results suggest a new approach for achieving 3D magnetic TI phases in such superlattices which is applicable to a large family of thallium rare-earth dichalcogenides and is expected to yield a fertile and tunable playground for exotic topological physics.
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Affiliation(s)
- Alexandra Yu. Vyazovskaya
- Laboratory of Nanostructured Surfaces and Coatings, Tomsk State University, Tomsk 634050, Russia
- Laboratory of Electronic and Spin Structure of Nanosystems, St. Petersburg State University, St. Petersburg 198504, Russia
| | - Evgeniy K. Petrov
- Laboratory of Nanostructured Surfaces and Coatings, Tomsk State University, Tomsk 634050, Russia
- Laboratory of Electronic and Spin Structure of Nanosystems, St. Petersburg State University, St. Petersburg 198504, Russia
| | - Yury M. Koroteev
- Laboratory of Electronic and Spin Structure of Nanosystems, St. Petersburg State University, St. Petersburg 198504, Russia
- Institute of Strength Physics and Materials Science, Tomsk 634021, Russia
| | - Mihovil Bosnar
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Basque Country, Spain
- Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología, Facultad de Ciencias Químicas, Universidad del País Vasco UPV/EHU, 20080 Donostia-San Sebastián, Basque Country, Spain
| | - Igor V. Silkin
- Laboratory of Nanostructured Surfaces and Coatings, Tomsk State University, Tomsk 634050, Russia
| | - Evgueni V. Chulkov
- Laboratory of Electronic and Spin Structure of Nanosystems, St. Petersburg State University, St. Petersburg 198504, Russia
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Basque Country, Spain
- Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología, Facultad de Ciencias Químicas, Universidad del País Vasco UPV/EHU, 20080 Donostia-San Sebastián, Basque Country, Spain
| | - Mikhail M. Otrokov
- Centro de Física de Materiales (CFM-MPC), Centro Mixto CSIC-UPV/EHU, 20018 Donostia-San Sebastián, Basque Country, Spain
- IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Basque Country, Spain
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Łepkowski SP. Advances in Topological Materials: Fundamentals, Challenges and Outlook. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3522. [PMID: 36234650 PMCID: PMC9565853 DOI: 10.3390/nano12193522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 09/27/2022] [Indexed: 06/16/2023]
Abstract
The discovery of topological insulators, characterized by an energy gap in bulk electronic band structures and metallic states on boundaries, has greatly inspired studies on the topological properties of the electronic band structures of crystalline materials [...].
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Affiliation(s)
- Sławomir P Łepkowski
- Institute of High Pressure Physics-Unipress, Polish Academy of Sciences, ul. Sokołowska 29/37, 01-142 Warszawa, Poland
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