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Li Q, Di Bernardo I, Maniatis J, McEwen D, Dominguez-Celorrio A, Bhuiyan MTH, Zhao M, Tadich A, Watson L, Lowe B, Vu THY, Trang CX, Hwang J, Mo SK, Fuhrer MS, Edmonds MT. Imaging the Breakdown and Restoration of Topological Protection in Magnetic Topological Insulator MnBi 2 Te 4. Adv Mater 2024:e2312004. [PMID: 38402422 DOI: 10.1002/adma.202312004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2023] [Revised: 02/20/2024] [Indexed: 02/26/2024]
Abstract
Quantum anomalous Hall (QAH) insulators transport charge without resistance along topologically protected chiral 1D edge states. Yet, in magnetic topological insulators to date, topological protection is far from robust, with zero-magnetic field QAH effect only realized at temperatures an order of magnitude below the Néel temperature TN , though small magnetic fields can stabilize QAH effect. Understanding why topological protection breaks down is therefore essential to realizing QAH effect at higher temperatures. Here a scanning tunneling microscope is used to directly map the size of exchange gap (Eg,ex ) and its spatial fluctuation in the QAH insulator 5-layer MnBi2 Te4 . Long-range fluctuations of Eg,ex are observed, with values ranging between 0 (gapless) and 70 meV, appearing to be uncorrelated to individual surface point defects. The breakdown of topological protection is directly imaged, showing that the gapless edge state, the hallmark signature of a QAH insulator, hybridizes with extended gapless regions in the bulk. Finally, it is unambiguously demonstrated that the gapless regions originate from magnetic disorder, by demonstrating that a small magnetic field restores Eg,ex in these regions, explaining the recovery of topological protection in magnetic fields. The results indicate that overcoming magnetic disorder is the key to exploiting the unique properties of QAH insulators.
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Affiliation(s)
- Qile Li
- School of Physics and Astronomy, Monash University, Clayton, Victoria, 3168, Australia
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria, Australia
| | - Iolanda Di Bernardo
- School of Physics and Astronomy, Monash University, Clayton, Victoria, 3168, Australia
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria, Australia
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Madrid, 28049, Spain
| | - Johnathon Maniatis
- School of Physics and Astronomy, Monash University, Clayton, Victoria, 3168, Australia
| | - Daniel McEwen
- School of Physics and Astronomy, Monash University, Clayton, Victoria, 3168, Australia
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria, Australia
| | - Amelia Dominguez-Celorrio
- School of Physics and Astronomy, Monash University, Clayton, Victoria, 3168, Australia
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria, Australia
| | - Mohammad T H Bhuiyan
- School of Physics and Astronomy, Monash University, Clayton, Victoria, 3168, Australia
| | - Mengting Zhao
- School of Physics and Astronomy, Monash University, Clayton, Victoria, 3168, Australia
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria, Australia
- Australian Synchrotron, Clayton, Victoria, 3168, Australia
| | - Anton Tadich
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria, Australia
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Madrid, 28049, Spain
| | - Liam Watson
- School of Physics and Astronomy, Monash University, Clayton, Victoria, 3168, Australia
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria, Australia
| | - Benjamin Lowe
- School of Physics and Astronomy, Monash University, Clayton, Victoria, 3168, Australia
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria, Australia
| | - Thi-Hai-Yen Vu
- School of Physics and Astronomy, Monash University, Clayton, Victoria, 3168, Australia
| | - Chi Xuan Trang
- School of Physics and Astronomy, Monash University, Clayton, Victoria, 3168, Australia
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria, Australia
| | - Jinwoong Hwang
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Physics and Institute of Quantum Convergence Technology, Kangwon National University, Chuncheon, 24341, Republic of Korea
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Michael S Fuhrer
- School of Physics and Astronomy, Monash University, Clayton, Victoria, 3168, Australia
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria, Australia
| | - Mark T Edmonds
- School of Physics and Astronomy, Monash University, Clayton, Victoria, 3168, Australia
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria, Australia
- ANFF-VIC Technology Fellow, Melbourne Centre for Nanofabrication, Victorian Node of, the Australian National Fabrication Facility, Clayton, Victoria, 3168, Australia
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Kholil MI, Bhuiyan MTH, Rahman MA, Ali MS, Aftabuzzaman M. Influence of molybdenum and technetium doping on visible light absorption, optical and electronic properties of lead-free perovskite CsSnBr 3 for optoelectronic applications. RSC Adv 2021; 11:2405-2414. [PMID: 35424182 PMCID: PMC8693675 DOI: 10.1039/d0ra09853a] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 01/03/2021] [Indexed: 11/21/2022] Open
Abstract
Lead-free metal halide perovskites have nowadays become familiar owing to their potential use in solar cells and other optoelectronic applications. In this study, we carried out the structural, elastic, electronic, and optical properties of pure and metal (Mo/Tc) doped CsSnBr3 by using the density functional theory. The metal doping CsSnBr3 displays a narrowing band gap and as a result the optical functions exhibit high absorption and high conductivity in the visible region. Metal doping samples also reveal a high dielectric constant which indicates a low charge-carrier recombination rate and hence enhances the device performance. The optical absorption spectra of metal doped samples greatly shifted (red-shift) towards the lower energy region compared with the pure sample which creates a high-intensity peak in the visible region. The mechanical parameter reveals a highly ductile, soft, and flexible nature which indicates the suitability for use in thin films. The electronic band structure of metal-doped CsSnBr3 shows an intermediate state that assists the excited electron to pass on from valence band to conduction band. The overall study suggests that lead-free CsSn0.875Tc0.125Br3 perovskite is a promising candidate for solar cells and other optoelectronic applications.
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Affiliation(s)
- M I Kholil
- Department of Physics, Pabna University of Science and Technology Pabna 6600 Bangladesh
| | - M T H Bhuiyan
- Department of Physics, Pabna University of Science and Technology Pabna 6600 Bangladesh
| | - M Atikur Rahman
- Department of Physics, Pabna University of Science and Technology Pabna 6600 Bangladesh
| | - M S Ali
- Department of Physics, Pabna University of Science and Technology Pabna 6600 Bangladesh
| | - M Aftabuzzaman
- Department of Physics, Pabna University of Science and Technology Pabna 6600 Bangladesh
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