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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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Conway MA, Earl SK, Muir JB, Vu THY, Tollerud JO, Watanabe K, Taniguchi T, Fuhrer MS, Edmonds MT, Davis JA. Effects of Floquet Engineering on the Coherent Exciton Dynamics in Monolayer WS 2. ACS Nano 2023. [PMID: 37494826 DOI: 10.1021/acsnano.3c01318] [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] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/28/2023]
Abstract
Coherent optical manipulation of electronic bandstructures via Floquet Engineering is a promising means to control quantum systems on an ultrafast time scale. However, the ultrafast switching on/off of the driving field comes with questions regarding the limits of the Floquet formalism (which is defined for an infinite periodic drive) through the switching process and to what extent the transient changes can be driven adiabatically. Experimentally addressing these questions has been difficult, in large part due to the absence of an established technique to measure coherent dynamics through the duration of the pulse. Here, using multidimensional coherent spectroscopy we explicitly excite, control, and probe a coherent superposition of excitons in the K and K' valleys in monolayer WS2. With a circularly polarized, red-detuned pump pulse, the degeneracy of the K and K' excitons can be lifted, and the phase of the coherence rotated. We directly measure phase rotations greater than π during the 100 fs driving pulse and show that this can be described by a combination of the AC-Stark shift of excitons in one valley and the Bloch-Siegert shift of excitons in the opposite valley. Despite showing a smooth evolution of the phase that directly follows the intensity envelope of the nonresonant pump pulse, the process is not perfectly adiabatic. By measuring the magnitude of the macroscopic coherence as it evolves before, during, and after the nonresonant pump pulse we show that there is additional decoherence caused by power broadening in the presence of the nonresonant pump. This nonadiabaticity arises as a result of interactions with the otherwise adiabatic Floquet states and may be a problem for many applications, such as manipulating qubits in quantum information processing; however, these measurements also suggest ways such effects can be minimized or eliminated.
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Affiliation(s)
- Mitchell A Conway
- Optical Sciences Centre, Swinburne University of Technology, Hawthorn, 3122, Victoria, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Swinburne University of Technology, Hawthorn, 3122, Victoria, Australia
| | - Stuart K Earl
- Optical Sciences Centre, Swinburne University of Technology, Hawthorn, 3122, Victoria, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Swinburne University of Technology, Hawthorn, 3122, Victoria, Australia
| | - Jack B Muir
- Optical Sciences Centre, Swinburne University of Technology, Hawthorn, 3122, Victoria, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Swinburne University of Technology, Hawthorn, 3122, Victoria, Australia
| | - Thi-Hai-Yen Vu
- ARC Centre of Excellence in Future Low-Energy Electronics Technology, Monash University, Clayton, 3800, Victoria, Australia
- School of Physics and Astronomy, Monash University, Clayton, 3800, Victoria, Australia
| | - Jonathan O Tollerud
- Optical Sciences Centre, Swinburne University of Technology, Hawthorn, 3122, Victoria, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Swinburne University of Technology, Hawthorn, 3122, Victoria, Australia
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Michael S Fuhrer
- ARC Centre of Excellence in Future Low-Energy Electronics Technology, Monash University, Clayton, 3800, Victoria, Australia
- School of Physics and Astronomy, Monash University, Clayton, 3800, Victoria, Australia
| | - Mark T Edmonds
- ARC Centre of Excellence in Future Low-Energy Electronics Technology, Monash University, Clayton, 3800, Victoria, Australia
- ANFF-VIC Technology Fellow, Melbourne Centre for Nanofabrication, Victorian Node of the Australian National Fabrication Facility, Clayton, Victoria 3168, Australia
| | - Jeffrey A Davis
- Optical Sciences Centre, Swinburne University of Technology, Hawthorn, 3122, Victoria, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Swinburne University of Technology, Hawthorn, 3122, Victoria, Australia
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Vu THY, Chen W, Deng X, Lau CFJ, Huang S, Ho-Baillie A, Jia B, Wen X. Visualizing the Impact of Light Soaking on Morphological Domains in an Operational Cesium Lead Halide Perovskite Solar Cell. J Phys Chem Lett 2020; 11:136-143. [PMID: 31829600 DOI: 10.1021/acs.jpclett.9b03210] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The dynamics of photogenerated carriers and mobile ions in operational cesium lead halide (CsPbI3) perovskite solar cells (PSCs) under working conditions are studied using nanoscale-resolved fluorescence lifetime imaging microscopy (FLIM). The temporally and spatially resolved photoluminescence (PL) changes in the perovskite film during and after bias light soaking are dynamically monitored. Through the analysis of the dynamic variations of PL intensity and PL lifetime of an open-circuit PSC, the impacts of light soaking are revealed by a dynamic model of photogenerated charge carrier and mobile ions. We confirmed the different behaviors between morphological domain interiors and domain boundaries during light soaking, which shed light on the engineering of the domain interiors in addition to the commonly considered domain boundary strategies. This work provides a full picture of the photogenerated process in an operational PSC and therefore guides the design and operation of perovskite-based optoelectronic devices.
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Affiliation(s)
- Thi-Hai-Yen Vu
- Centre for Translational Atomaterials , Swinburne University of Technology , Hawthorn , Victoria 3122 , Australia
| | - Weijian Chen
- Centre for Translational Atomaterials , Swinburne University of Technology , Hawthorn , Victoria 3122 , Australia
| | - Xiaofan Deng
- Australian Centre for Advanced Photovoltaics, School of Photovoltaic and Renewable Energy Engineering , UNSW Sydney , Sydney 2052 , Australia
| | - Cho Fai Jonathan Lau
- Australian Centre for Advanced Photovoltaics, School of Photovoltaic and Renewable Energy Engineering , UNSW Sydney , Sydney 2052 , Australia
| | - Shujuan Huang
- Australian Centre for Advanced Photovoltaics, School of Photovoltaic and Renewable Energy Engineering , UNSW Sydney , Sydney 2052 , Australia
| | - Anita Ho-Baillie
- Australian Centre for Advanced Photovoltaics, School of Photovoltaic and Renewable Energy Engineering , UNSW Sydney , Sydney 2052 , Australia
| | - Baohua Jia
- Centre for Translational Atomaterials , Swinburne University of Technology , Hawthorn , Victoria 3122 , Australia
| | - Xiaoming Wen
- Centre for Translational Atomaterials , Swinburne University of Technology , Hawthorn , Victoria 3122 , Australia
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