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Zhang Y, Chen K, Yang SH. Breaking the limitations with sparse inputs by variational frameworks (BLIss) in terahertz super-resolution 3D reconstruction. OPTICS EXPRESS 2024; 32:15078-15092. [PMID: 38859167 DOI: 10.1364/oe.510670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 03/27/2024] [Indexed: 06/12/2024]
Abstract
Data acquisition, image processing, and image quality are the long-lasting issues for terahertz (THz) 3D reconstructed imaging. Existing methods are primarily designed for 2D scenarios, given the challenges associated with obtaining super-resolution (SR) data and the absence of an efficient SR 3D reconstruction framework in conventional computed tomography (CT). Here, we demonstrate BLIss, a new approach for THz SR 3D reconstruction with sparse 2D data input. BLIss seamlessly integrates conventional CT techniques and variational framework with the core of the adapted Euler-Elastica-based model. The quantitative 3D image evaluation metrics, including the standard deviation of Gaussian, mean curvatures, and the multi-scale structural similarity index measure (MS-SSIM), validate the superior smoothness and fidelity achieved with our variational framework approach compared with conventional THz CT modal. Beyond its contributions to advancing THz SR 3D reconstruction, BLIss demonstrates potential applicability in other imaging modalities, such as X-ray and MRI. This suggests extensive impacts on the broader field of imaging applications.
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2
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Feng J, Zhou X, Xu M, Shi J, Li Y. Layer Control of Magneto-Optical Effects and Their Quantization in Spin-Valley Splitting Antiferromagnets. NANO LETTERS 2024; 24:3898-3905. [PMID: 38525906 DOI: 10.1021/acs.nanolett.3c05052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/26/2024]
Abstract
Magneto-optical effects (MOE), interfacing the fundamental interplay between magnetism and light, have served as a powerful probe for magnetic order, band topology, and valley index. Here, based on multiferroic and topological bilayer antiferromagnets (AFMs), we propose a layer control of MOE (L-MOE), which is created and annihilated by layer-stacking or an electric field effect. The key character of L-MOE is the sign-reversible response controlled by ferroelectric polarization, the Néel vector, or the electric field direction. Moreover, the sign-reversible L-MOE can be quantized in topologically insulating AFMs. We reveal that the switchable L-MOE originates from the combined contributions of spin-conserving and spin-flip interband transitions in spin-valley splitting AFMs, a phenomenon not observed in conventional AFMs. Our findings bridge the ancient MOE to the emergent realms of layertronics, valleytronics, and multiferroics and may hold immense potential in these fields.
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Affiliation(s)
- Jiaqi Feng
- Laboratory of Quantum Functional Materials Design and Application, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116, China
| | - Xiaodong Zhou
- Laboratory of Quantum Functional Materials Design and Application, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116, China
| | - Meiling Xu
- Laboratory of Quantum Functional Materials Design and Application, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116, China
| | - Jingming Shi
- Laboratory of Quantum Functional Materials Design and Application, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116, China
| | - Yinwei Li
- Laboratory of Quantum Functional Materials Design and Application, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116, China
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3
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Jiang Y, Wang H, Bao K, Liu Z, Wang J. Monolayer V_{2}MX_{4}: A New Family of Quantum Anomalous Hall Insulators. PHYSICAL REVIEW LETTERS 2024; 132:106602. [PMID: 38518306 DOI: 10.1103/physrevlett.132.106602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 10/18/2023] [Accepted: 02/09/2024] [Indexed: 03/24/2024]
Abstract
We theoretically propose that the van der Waals layered ternary transition metal chalcogenide V_{2}MX_{4} (M=W, Mo; X=S, Se) is a new family of quantum anomalous Hall insulators with sizable bulk gap and Chern number C=-1. The large topological gap originates from the deep band inversion between spin-up bands contributed by d_{xz}, d_{yz} orbitals of V and spin-down band from d_{z^{2}} orbital of M at the Fermi level. Remarkably, the Curie temperature of monolayer V_{2}MX_{4} is predicted to be much higher than that of monolayer MnBi_{2}Te_{4}. Furthermore, the thickness dependence of the Chern number for few multilayers shows interesting oscillating behavior. The general physics from the d orbitals here applies to a large class of ternary transition metal chalcogenide such as Ti_{2}WX_{4} with the space group P-42m. These interesting predictions, if realized experimentally, could greatly promote the research and application of topological quantum physics.
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Affiliation(s)
- Yadong Jiang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Huan Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Kejie Bao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Zhaochen Liu
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Jing Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute for Nanoelectronic Devices and Quantum Computing, Zhangjiang Fudan International Innovation Center, Fudan University, Shanghai 200433, China
- Hefei National Laboratory, Hefei 230088, China
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4
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Wan Y, Li J, Liu Q. Topological magnetoelectric response in ferromagnetic axion insulators. Natl Sci Rev 2024; 11:nwac138. [PMID: 38264342 PMCID: PMC10804227 DOI: 10.1093/nsr/nwac138] [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: 12/06/2021] [Revised: 06/22/2022] [Accepted: 06/23/2022] [Indexed: 01/25/2024] Open
Abstract
The topological magnetoelectric effect (TME) is a hallmark response of the topological field theory, which provides a paradigm shift in the study of emergent topological phenomena. However, its direct observation is yet to be realized due to the demanding magnetic configuration required to gap all surface states. Here, we theoretically propose that axion insulators with a simple ferromagnetic configuration, such as the MnBi2Te4/(Bi2Te3)n family, provide an ideal playground to realize the TME. In the designed triangular prism geometry, all the surface states are magnetically gapped. Under a vertical electric field, the surface Hall currents give rise to a nearly half-quantized orbital moment, accompanied by a gapless chiral hinge mode circulating in parallel. Thus, the orbital magnetization from the two topological origins can be easily distinguished by reversing the electric field. Our work paves the way for direct observation of the TME in realistic axion-insulator materials.
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Affiliation(s)
- Yuhao Wan
- Department of Physics and Shenzhen Institute for Quantum Science and Engineering (SIQSE), Southern University of Science and Technology, Shenzhen 518055, China
| | - Jiayu Li
- Department of Physics and Shenzhen Institute for Quantum Science and Engineering (SIQSE), Southern University of Science and Technology, Shenzhen 518055, China
| | - Qihang Liu
- Department of Physics and Shenzhen Institute for Quantum Science and Engineering (SIQSE), Southern University of Science and Technology, Shenzhen 518055, China
- Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen 518055, China
- Guangdong Provincial Key Laboratory for Computational Science and Material Design, Southern University of Science and Technology, Shenzhen 518055, China
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5
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Han X, Yi HT, Oh S, Wu L. Magneto-optical Effects of an Artificially Layered Ferromagnetic Topological Insulator with a TC of 160 K. NANO LETTERS 2024; 24:914-919. [PMID: 38190329 DOI: 10.1021/acs.nanolett.3c04103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2024]
Abstract
Magnetic topological insulators are a fertile platform for studying the interplay between magnetism and topology. The unique electronic band structure can induce exotic transport and optical properties. However, a comprehensive optical study at both near-infrared and terahertz frequencies has been lacking. Here, we report magneto-optical effects from a heterostructure of a Cr-incorporated topological insulator, CBST. By measuring the magneto-optical Kerr effect, we observe a high temperature ferromagnetic transition (160 K) in the CBST film. We also use time-domain terahertz polarimetry to reveal a terahertz Faraday rotation of 1.5 mrad and a terahertz Kerr rotation of 3.6 mrad at 2 K. The calculated terahertz Hall conductance is 0.42 e2/h. Our work shows the optical responses of an artificially layered magnetic topological insulator, paving the way toward a high-temperature quantum anomalous Hall effect via heterostructure engineering.
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Affiliation(s)
- Xingyue Han
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Hee Taek Yi
- Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Seongshik Oh
- Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Liang Wu
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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6
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Zhu WQ, Shan WY. Theoretical studies of magneto-optical Kerr and Faraday effects in two-dimensional second-order topological insulators. Sci Rep 2023; 13:12599. [PMID: 37537224 PMCID: PMC10400575 DOI: 10.1038/s41598-023-39644-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Accepted: 07/28/2023] [Indexed: 08/05/2023] Open
Abstract
Optical approaches are useful for studying the electronic and spin structure of materials. Here, based on the tight-binding model and linear response theory, we investigate the magneto-optical Kerr and Faraday effects in two-dimensional second-order topological insulators (SOTI) with external magnetization. We find that orbital-dependent Zeeman term induces band crossings for SOTI phase, which are absent for trivial phase. In the weak-magnetization regime, these crossings give rise to giant jumps (peaks) of Kerr and Faraday angles (ellipticity) for SOTI phase. In the strong-magnetization regime, we find that two nearly flat bands are formed at the high-symmetry point of Brillouin zone of SOTI phase. These flat bands give rise to two successive giant jumps (peaks) of Kerr and Faraday angles (ellipticity). These phenomena provide new possibilities to characterize and detect the two-dimensional SOTI phase.
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Affiliation(s)
- Wan-Qing Zhu
- Department of Physics, School of Physics and Materials Science, Guangzhou University, Guangzhou, 510006, China
| | - Wen-Yu Shan
- Department of Physics, School of Physics and Materials Science, Guangzhou University, Guangzhou, 510006, China.
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Matsuda T, Higo T, Koretsune T, Kanda N, Hirai Y, Peng H, Matsuo T, Yoshikawa N, Shimano R, Nakatsuji S, Matsunaga R. Ultrafast Dynamics of Intrinsic Anomalous Hall Effect in the Topological Antiferromagnet Mn_{3}Sn. PHYSICAL REVIEW LETTERS 2023; 130:126302. [PMID: 37027855 DOI: 10.1103/physrevlett.130.126302] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 02/06/2023] [Indexed: 06/19/2023]
Abstract
We investigate ultrafast dynamics of the anomalous Hall effect (AHE) in the topological antiferromagnet Mn_{3}Sn with sub-100 fs time resolution. Optical pulse excitations largely elevate the electron temperature up to 700 K, and terahertz probe pulses clearly resolve ultrafast suppression of the AHE before demagnetization. The result is well reproduced by microscopic calculation of the intrinsic Berry-curvature mechanism while the extrinsic contribution is clearly excluded. Our work opens a new avenue for the study of nonequilibrium AHE to identify the microscopic origin by drastic control of the electron temperature by light.
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Affiliation(s)
- Takuya Matsuda
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Tomoya Higo
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | | | - Natsuki Kanda
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Yoshua Hirai
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Hanyi Peng
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Takumi Matsuo
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Naotaka Yoshikawa
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Ryo Shimano
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
- Cryogenic Research Center, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0032, Japan
| | - Satoru Nakatsuji
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
- Trans-scale Quantum Science Institute, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, 21218 Maryland, USA
| | - Ryusuke Matsunaga
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- Trans-scale Quantum Science Institute, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
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8
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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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9
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Theory of optical axion electrodynamics and application to the Kerr effect in topological antiferromagnets. Nat Commun 2022; 13:7615. [PMID: 36494356 PMCID: PMC9734152 DOI: 10.1038/s41467-022-35248-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Accepted: 11/23/2022] [Indexed: 12/13/2022] Open
Abstract
Emergent axion electrodynamics in magneto-electric media is expected to provide novel ways to detect and control material properties with electromagnetic fields. However, despite being studied intensively for over a decade, its theoretical understanding remains mostly confined to the static limit. Here, we introduce a theory of axion electrodynamics at general frequencies. We define a proper optical axion magneto-electric coupling through its relation to optical surface Hall conductivity and provide ways to calculate it in lattice systems. By employing our formulas, we show that axion electrodynamics can lead to a significant Kerr effect in thin-film antiferromagnets at wavelengths that are seemingly too long to resolve the spatial modulation of magnetism. We identify the wavelength scale above which the Kerr effect is suppressed. Our theory is particularly relevant to materials like MnBi2Te4, a topological antiferromagnet whose magneto-electric response is shown here to be dominated by the axion contribution even at optical frequencies.
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10
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Aishwarya A, Cai Z, Raghavan A, Romanelli M, Wang X, Li X, Gu GD, Hirsbrunner M, Hughes T, Liu F, Jiao L, Madhavan V. Spin-selective tunneling from nanowires of the candidate topological Kondo insulator SmB 6. Science 2022; 377:1218-1222. [PMID: 36074835 DOI: 10.1126/science.abj8765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Incorporating relativistic physics into quantum tunneling can lead to exotic behavior such as perfect transmission through Klein tunneling. Here, we probed the tunneling properties of spin-momentum-locked relativistic fermions by designing and implementing a tunneling geometry that uses nanowires of the topological Kondo insulator candidate samarium hexaboride. The nanowires are attached to the end of scanning tunneling microscope tips and used to image the bicollinear stripe spin order in the antiferromagnet Fe1.03Te with a Neel temperature of about 50 kelvin. The antiferromagnetic stripes become invisible above 10 kelvin concomitant with the suppression of the topological surface states in the tip. We further demonstrate that the direction of spin polarization is tied to the tunneling direction. Our technique establishes samarium hexaboride nanowires as ideal conduits for spin-polarized currents.
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Affiliation(s)
- Anuva Aishwarya
- Department of Physics and Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Zhuozhen Cai
- Department of Physics and Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Arjun Raghavan
- Department of Physics and Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Marisa Romanelli
- Department of Physics and Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Xiaoyu Wang
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
| | - Xu Li
- State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, and School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, China
| | - G D Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Mark Hirsbrunner
- Department of Physics and Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Taylor Hughes
- Department of Physics and Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Fei Liu
- State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, and School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, China
| | - Lin Jiao
- Department of Physics and Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.,National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
| | - Vidya Madhavan
- Department of Physics and Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
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11
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He QL, Hughes TL, Armitage NP, Tokura Y, Wang KL. Topological spintronics and magnetoelectronics. NATURE MATERIALS 2022; 21:15-23. [PMID: 34949869 DOI: 10.1038/s41563-021-01138-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 09/21/2021] [Indexed: 05/08/2023]
Abstract
Topological electronic materials, such as topological insulators, are distinct from trivial materials in the topology of their electronic band structures that lead to robust, unconventional topological states, which could bring revolutionary developments in electronics. This Perspective summarizes developments of topological insulators in various electronic applications including spintronics and magnetoelectronics. We group and analyse several important phenomena in spintronics using topological insulators, including spin-orbit torque, the magnetic proximity effect, interplay between antiferromagnetism and topology, and the formation of topological spin textures. We also outline recent developments in magnetoelectronics such as the axion insulator and the topological magnetoelectric effect observed using different topological insulators.
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Affiliation(s)
- Qing Lin He
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, China.
- Collaborative Innovation Center of Quantum Matter, Beijing, China.
- Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, Beijing, China.
| | - Taylor L Hughes
- Department of Physics and Institute for Condensed Matter Theory, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - N Peter Armitage
- Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD, USA
| | - Yoshinori Tokura
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
- Tokyo College, University of Tokyo, Tokyo, Japan
| | - Kang L Wang
- Department of Electrical and Computer Engineering, University of California, Los Angeles, CA, USA.
- Center of Quantum Sciences and Engineering, University of California, Los Angeles, CA, USA.
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12
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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: 11] [Impact Index Per Article: 3.7] [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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13
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Abstract
We give an overview of the work done during the past ten years on the Casimir interaction in electronic topological materials, our focus being solids, which possess surface or bulk electronic band structures with nontrivial topologies, which can be evinced through optical properties that are characterizable in terms of nonzero topological invariants. The examples we review are three-dimensional magnetic topological insulators, two-dimensional Chern insulators, graphene monolayers exhibiting the relativistic quantum Hall effect, and time reversal symmetry-broken Weyl semimetals, which are fascinating systems in the context of Casimir physics. Firstly, this is for the reason that they possess electromagnetic properties characterizable by axial vectors (because of time reversal symmetry breaking), and, depending on the mutual orientation of a pair of such axial vectors, two systems can experience a repulsive Casimir–Lifshitz force, even though they may be dielectrically identical. Secondly, the repulsion thus generated is potentially robust against weak disorder, as such repulsion is associated with the Hall conductivity that is topologically protected in the zero-frequency limit. Finally, the far-field low-temperature behavior of the Casimir force of such systems can provide signatures of topological quantization.
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14
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Seifert TS, Martens U, Radu F, Ribow M, Berritta M, Nádvorník L, Starke R, Jungwirth T, Wolf M, Radu I, Münzenberg M, Oppeneer PM, Woltersdorf G, Kampfrath T. Frequency-Independent Terahertz Anomalous Hall Effect in DyCo 5 , Co 32 Fe 68 , and Gd 27 Fe 73 Thin Films from DC to 40 THz. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2007398. [PMID: 33656190 DOI: 10.1002/adma.202007398] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 12/21/2020] [Indexed: 06/12/2023]
Abstract
The anomalous Hall effect (AHE) is a fundamental spintronic charge-to-charge-current conversion phenomenon and closely related to spin-to-charge-current conversion by the spin Hall effect. Future high-speed spintronic devices will crucially rely on such conversion phenomena at terahertz (THz) frequencies. Here, it is revealed that the AHE remains operative from DC up to 40 THz with a flat frequency response in thin films of three technologically relevant magnetic materials: DyCo5 , Co32 Fe68 , and Gd27 Fe73 . The frequency-dependent conductivity-tensor elements σxx and σyx are measured, and good agreement with DC measurements is found. The experimental findings are fully consistent with ab initio calculations of σyx for CoFe and highlight the role of the large Drude scattering rate (≈100 THz) of metal thin films, which smears out any sharp spectral features of the THz AHE. Finally, it is found that the intrinsic contribution to the THz AHE dominates over the extrinsic mechanisms for the Co32 Fe68 sample. The results imply that the AHE and related effects such as the spin Hall effect are highly promising ingredients of future THz spintronic devices reliably operating from DC to 40 THz and beyond.
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Affiliation(s)
- Tom S Seifert
- Department of Physics, Freie Universität Berlin, Berlin, 14195, Germany
- Department of Physical Chemistry, Fritz-Haber-Institute of the Max-Planck-Society, Berlin, 14195, Germany
| | - Ulrike Martens
- Institute of Physics, University of Greifswald, Greifswald, 17489, Germany
| | - Florin Radu
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, Berlin, 12489, Germany
| | - Mirkow Ribow
- Institute of Physics, Martin-Luther Universität Halle-Wittenberg, Halle (Saale), 06120, Germany
| | - Marco Berritta
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, Uppsala, SE-75120, Sweden
| | - Lukáš Nádvorník
- Faculty of Mathematics and Physics, Charles University, Ke Kalovu 2027/3, Prague, 12116, Czech Republic
| | | | - Tomas Jungwirth
- Institute of Physics, Czech Academy of Sciences, Cukrovarnicka 10, Praha, 6, 162 00, Czech Republic
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Martin Wolf
- Department of Physical Chemistry, Fritz-Haber-Institute of the Max-Planck-Society, Berlin, 14195, Germany
| | - Ilie Radu
- Department of Physics, Freie Universität Berlin, Berlin, 14195, Germany
- Max-Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Str. 2A, Berlin, 12489, Germany
| | - Markus Münzenberg
- Institute of Physics, University of Greifswald, Greifswald, 17489, Germany
| | - Peter M Oppeneer
- Institute of Physics, Martin-Luther Universität Halle-Wittenberg, Halle (Saale), 06120, Germany
| | - Georg Woltersdorf
- Institute of Physics, Martin-Luther Universität Halle-Wittenberg, Halle (Saale), 06120, Germany
| | - Tobias Kampfrath
- Department of Physics, Freie Universität Berlin, Berlin, 14195, Germany
- Department of Physical Chemistry, Fritz-Haber-Institute of the Max-Planck-Society, Berlin, 14195, Germany
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15
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Baydin A, Makihara T, Peraca NM, Kono J. Time-domain terahertz spectroscopy in high magnetic fields. FRONTIERS OF OPTOELECTRONICS 2021; 14:110-129. [PMID: 36637783 PMCID: PMC9743882 DOI: 10.1007/s12200-020-1101-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 10/29/2020] [Indexed: 06/14/2023]
Abstract
There are a variety of elementary and collective terahertz-frequency excitations in condensed matter whose magnetic field dependence contains significant insight into the states and dynamics of the electrons involved. Often, determining the frequency, temperature, and magnetic field dependence of the optical conductivity tensor, especially in high magnetic fields, can clarify the microscopic physics behind complex many-body behaviors of solids. While there are advanced terahertz spectroscopy techniques as well as high magnetic field generation techniques available, a combination of the two has only been realized relatively recently. Here, we review the current state of terahertz time-domain spectroscopy (THz-TDS) experiments in high magnetic fields. We start with an overview of time-domain terahertz detection schemes with a special focus on how they have been incorporated into optically accessible high-field magnets. Advantages and disadvantages of different types of magnets in performing THz-TDS experiments are also discussed. Finally, we highlight some of the new fascinating physical phenomena that have been revealed by THz-TDS in high magnetic fields.
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Affiliation(s)
- Andrey Baydin
- Department of Electrical and Computer Engineering, Rice University, Houston, TX, 70005, USA.
| | - Takuma Makihara
- Department of Physics and Astronomy, Rice University, Houston, Texas, 77005, USA
| | | | - Junichiro Kono
- Department of Electrical and Computer Engineering, Rice University, Houston, TX, 70005, USA.
- Department of Physics and Astronomy, Rice University, Houston, Texas, 77005, USA.
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas, 77005, USA.
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16
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Yu J, Song ZD, Liu CX. Gapless Criterion for Crystals from Effective Axion Field. PHYSICAL REVIEW LETTERS 2020; 125:036401. [PMID: 32745391 DOI: 10.1103/physrevlett.125.036401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Accepted: 06/30/2020] [Indexed: 06/11/2023]
Abstract
Gapless criteria that can efficiently determine whether a crystal is gapless or not are particularly useful for identifying topological semimetals. In this work, we propose a sufficient gapless criterion for three-dimensional noninteracting crystals, based on the simplified expressions for the bulk average value of the static axion field. The brief logic is that two different simplified expressions give the same value in an insulator, and thus the gapless phase can be detected by the mismatch of them. We demonstrate the effectiveness of the gapless criterion in the magnetic systems with space groups 26 and 13, where mirror, glide, and inversion symmetries provide the simplified expressions. In particular, the gapless criterion can identify gapless phases that are missed by the symmetry-representation approach, as illustrated by space group 26. Our proposal serves as a guiding principle for future discovery of topological semimetals.
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Affiliation(s)
- Jiabin Yu
- Department of Physics, the Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Zhi-Da Song
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Chao-Xing Liu
- Department of Physics, the Pennsylvania State University, University Park, Pennsylvania 16802, USA
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17
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Peng K, Jevtics D, Zhang F, Sterzl S, Damry DA, Rothmann MU, Guilhabert B, Strain MJ, Tan HH, Herz LM, Fu L, Dawson MD, Hurtado A, Jagadish C, Johnston MB. Three-dimensional cross-nanowire networks recover full terahertz state. Science 2020; 368:510-513. [PMID: 32355027 DOI: 10.1126/science.abb0924] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 04/01/2020] [Indexed: 12/17/2022]
Abstract
Terahertz radiation encompasses a wide band of the electromagnetic spectrum, spanning from microwaves to infrared light, and is a particularly powerful tool for both fundamental scientific research and applications such as security screening, communications, quality control, and medical imaging. Considerable information can be conveyed by the full polarization state of terahertz light, yet to date, most time-domain terahertz detectors are sensitive to just one polarization component. Here we demonstrate a nanotechnology-based semiconductor detector using cross-nanowire networks that records the full polarization state of terahertz pulses. The monolithic device allows simultaneous measurements of the orthogonal components of the terahertz electric field vector without cross-talk. Furthermore, we demonstrate the capabilities of the detector for the study of metamaterials.
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Affiliation(s)
- Kun Peng
- Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, UK
| | - Dimitars Jevtics
- Institute of Photonics, SUPA Department of Physics, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow G1 1RD, UK
| | - Fanlu Zhang
- Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
| | - Sabrina Sterzl
- Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, UK
| | - Djamshid A Damry
- Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, UK
| | - Mathias U Rothmann
- Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, UK
| | - Benoit Guilhabert
- Institute of Photonics, SUPA Department of Physics, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow G1 1RD, UK
| | - Michael J Strain
- Institute of Photonics, SUPA Department of Physics, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow G1 1RD, UK
| | - Hark H Tan
- Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
| | - Laura M Herz
- Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, UK
| | - Lan Fu
- Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
| | - Martin D Dawson
- Institute of Photonics, SUPA Department of Physics, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow G1 1RD, UK
| | - Antonio Hurtado
- Institute of Photonics, SUPA Department of Physics, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow G1 1RD, UK
| | - Chennupati Jagadish
- Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
| | - Michael B Johnston
- Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, UK.
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18
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Matsuda T, Kanda N, Higo T, Armitage NP, Nakatsuji S, Matsunaga R. Room-temperature terahertz anomalous Hall effect in Weyl antiferromagnet Mn 3Sn thin films. Nat Commun 2020; 11:909. [PMID: 32060261 PMCID: PMC7021706 DOI: 10.1038/s41467-020-14690-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 01/24/2020] [Indexed: 12/03/2022] Open
Abstract
Antiferromagnetic spin motion at terahertz (THz) frequencies attracts growing interests for fast spintronics, however, their smaller responses to external field inhibit device application. Recently the noncollinear antiferromagnet Mn3Sn, a Weyl semimetal candidate, was reported to show large anomalous Hall effect (AHE) at room temperature comparable to ferromagnets. Dynamical aspect of such large responses is an important issue to be clarified for future THz data processing. Here the THz anomalous Hall conductivity in Mn3Sn thin films is investigated by polarization-resolved spectroscopy. Large anomalous Hall conductivity \documentclass[12pt]{minimal}
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\begin{document}$${\mathrm{Re}}\;\sigma _{xy}\left( \omega \right) \sim 20\;{\mathrm{\Omega }}^{ - 1}{\mathrm{cm}}^{ - 1}$$\end{document}Reσxyω~20Ω−1cm−1 at THz frequencies is clearly observed as polarization rotation. A peculiar temperature dependence corresponding to the breaking/recovery of symmetry in the spin texture is also discussed. Observation of the THz AHE at room temperature demonstrates the ultrafast readout for the antiferromagnetic spintronics using Mn3Sn, and will also open new avenue for studying nonequilibrium dynamics in Weyl antiferromagnets. Antiferromagnets promise great potential for spintronic applications due to their spin excitations at terahertz frequencies, however, read out of the spin state is hindered by the small response to external fields. Here the authors demonstrate all optical readout of the spin state of antiferromagnetic Mn3Sn at THz frequency.
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Affiliation(s)
- Takuya Matsuda
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - Natsuki Kanda
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - Tomoya Higo
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, 277-8581, Japan.,CREST, Japan Science and Technology Agency, Kawaguchi, Saitama, 332-0012, Japan
| | - N P Armitage
- The Institute of Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MA, 21218, USA
| | - Satoru Nakatsuji
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, 277-8581, Japan.,CREST, Japan Science and Technology Agency, Kawaguchi, Saitama, 332-0012, Japan.,The Institute of Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MA, 21218, USA.,Department of Physics, The University of Tokyo, Hongo, Bunkyo-Ku, Tokyo, 113-0033, Japan
| | - Ryusuke Matsunaga
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, 277-8581, Japan. .,PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan.
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19
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Feng W, Hanke JP, Zhou X, Guo GY, Blügel S, Mokrousov Y, Yao Y. Topological magneto-optical effects and their quantization in noncoplanar antiferromagnets. Nat Commun 2020; 11:118. [PMID: 31913308 PMCID: PMC6949225 DOI: 10.1038/s41467-019-13968-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 12/10/2019] [Indexed: 11/23/2022] Open
Abstract
Reflecting the fundamental interactions of polarized light with magnetic matter, magneto-optical effects are well known since more than a century. The emergence of these phenomena is commonly attributed to the interplay between exchange splitting and spin-orbit coupling in the electronic structure of magnets. Using theoretical arguments, we demonstrate that topological magneto-optical effects can arise in noncoplanar antiferromagnets due to the finite scalar spin chirality, without any reference to exchange splitting or spin-orbit coupling. We propose spectral integrals of certain magneto-optical quantities that uncover the unique topological nature of the discovered effect. We also find that the Kerr and Faraday rotation angles can be quantized in insulating topological antiferromagnets in the low-frequency limit, owing to nontrivial global properties that manifest in quantum topological magneto-optical effects. Although the predicted topological and quantum topological magneto-optical effects are fundamentally distinct from conventional light-matter interactions, they can be measured by readily available experimental techniques.
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Affiliation(s)
- Wanxiang Feng
- Key Lab of advanced optoelectronic quantum architecture and measurement (Ministry of Education), Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems, and School of Physics, Beijing Institute of Technology, 100081, Beijing, China
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425, Jülich, Germany
| | - Jan-Philipp Hanke
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425, Jülich, Germany
- Institute of Physics, Johannes Gutenberg University Mainz, 55099, Mainz, Germany
| | - Xiaodong Zhou
- Key Lab of advanced optoelectronic quantum architecture and measurement (Ministry of Education), Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems, and School of Physics, Beijing Institute of Technology, 100081, Beijing, China
| | - Guang-Yu Guo
- Department of Physics and Center for Theoretical Physics, National Taiwan University, Taipei, 10617, Taiwan
- Physics Division, National Center for Theoretical Sciences, Hsinchu, 30013, Taiwan
| | - Stefan Blügel
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425, Jülich, Germany
| | - Yuriy Mokrousov
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425, Jülich, Germany
- Institute of Physics, Johannes Gutenberg University Mainz, 55099, Mainz, Germany
| | - Yugui Yao
- Key Lab of advanced optoelectronic quantum architecture and measurement (Ministry of Education), Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems, and School of Physics, Beijing Institute of Technology, 100081, Beijing, China.
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20
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Pozo O, Repellin C, Grushin AG. Quantization in Chiral Higher Order Topological Insulators: Circular Dichroism and Local Chern Marker. PHYSICAL REVIEW LETTERS 2019; 123:247401. [PMID: 31922878 DOI: 10.1103/physrevlett.123.247401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Indexed: 06/10/2023]
Abstract
The robust quantization of observables in units of universal constants is a hallmark of topological phases. We show that chiral higher order topological insulators (HOTIs), bulk insulators with chiral hinge states, present two unusual features related to quantization. First, we show that circular dichroism is quantized to an integer or zero depending on the orientation of the sample. This probe locates the hinge states, and can be used to distinguish different types of chiral HOTIs. Second, we find that the average of the local Chern marker over a single surface, an observable related to the surface Hall conductivity known to be quantized in the infinite slab geometry, is nonuniversal for a finite surface. This is due to a nonuniversal contribution of the hinge states, previously unaccounted for, that distinguishes surfaces of chiral HOTIs from Chern insulators. Our findings are relevant to establish higher order topology in systems such as the axion insulator candidate EuIn_{2}As_{2}, and cold atomic realizations.
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Affiliation(s)
- Oscar Pozo
- Instituto de Ciencia de Materiales de Madrid, and CSIC, Cantoblanco, 28049 Madrid, Spain
| | - Cécile Repellin
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Adolfo G Grushin
- University Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38000 Grenoble, France
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21
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Boonchui S, Nualpijit P. New method of second quantization of the strained-graphene Kerr and Faraday rotations. OPTICS EXPRESS 2019; 27:28350-28363. [PMID: 31684588 DOI: 10.1364/oe.27.028350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 07/19/2019] [Indexed: 06/10/2023]
Abstract
We illustrate Kerr and Faraday rotation in the strained-graphene by applying the second quantization method as an alternative approach. We consider the right- and left-going photon fields coupling with strained graphene. In other words, we have a new stationary state solution describing this phenomenon. A single-photon polarization in the provided state is considered in cases of a non-magnetic field, and uniform strained graphene. We show that the optical l properties of Faraday rotation, reflectance, and transmittance depend on the spinor phase and the energy level of an electron in strained graphene. These values can be controlled by variation of a strain parameter and strain types. Then, it is possible to have an alternative measurement of the pseudo-spin state and electronic structure in the 2-D layer by observing the optical properties of the single-photon in the provided state.
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22
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Marsh DJE, Fong KC, Lentz EW, Šmejkal L, Ali MN. Proposal to Detect Dark Matter using Axionic Topological Antiferromagnets. PHYSICAL REVIEW LETTERS 2019; 123:121601. [PMID: 31633991 DOI: 10.1103/physrevlett.123.121601] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Indexed: 06/10/2023]
Abstract
Antiferromagnetically doped topological insulators (ATI) are among the candidates to host dynamical axion fields and axion polaritons, weakly interacting quasiparticles that are analogous to the dark axion, a long sought after candidate dark matter particle. Here we demonstrate that using the axion quasiparticle antiferromagnetic resonance in ATIs in conjunction with low-noise methods of detecting THz photons presents a viable route to detect axion dark matter with a mass of 0.7 to 3.5 meV, a range currently inaccessible to other dark matter detection experiments and proposals. The benefits of this method at high frequency are the tunability of the resonance with applied magnetic field, and the use of ATI samples with volumes much larger than 1 mm^{3}.
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Affiliation(s)
- David J E Marsh
- Institut für Astrophysik, Georg-August Universität, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
| | - Kin Chung Fong
- Raytheon BBN Technologies, Quantum Engineering and Computing, Cambridge, Massachusetts 02138, USA
| | - Erik W Lentz
- Institut für Astrophysik, Georg-August Universität, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
| | - Libor Šmejkal
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 53 Praha 6 Czech Republic
- Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2, Czech Republic
| | - Mazhar N Ali
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Saale), Germany
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23
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Shah M, Anwar MS. Magneto-optical effects in the Landau level manifold of 2D lattices with spin-orbit interaction. OPTICS EXPRESS 2019; 27:23217-23233. [PMID: 31510604 DOI: 10.1364/oe.27.023217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 07/17/2019] [Indexed: 06/10/2023]
Abstract
Silicene is a competitive and promising 2D material, possessing interesting topological, electronic and optical properties. The presence of strong spin orbit interaction in silicene and its analogues, germanene and tinene, leads to the opening of a gapin the energy spectrum and spin-splitting of the bands in each valley. Building upon prior work we discuss a general method to determine the magneto-optic response of silicene when a Gaussian beam is incident on silicene grown on a dielectric substrate in the presence of a static magnetic field. We use a semiclassical treatment to describe the Faraday rotation (FR) and Magneto-optical Kerr effect (MOKE). The response can be modulated both electrically and magnetically. We derive analytic expressions for valley and spin polarized FR and MOKE for arbitrary polarization of incident light in the terahertz regime. We demonstrate that large FR and MOKE can be achieved by tuning the electric field, magnetic fields and chemical potential in these fascinating 2D materials.
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24
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Zhou X, Zhang RW, Zhang Z, Ma DS, Feng W, Mokrousov Y, Yao Y. Fully Spin-Polarized Nodal Loop Semimetals in Alkaline Metal Monochalcogenide Monolayers. J Phys Chem Lett 2019; 10:3101-3108. [PMID: 31117678 DOI: 10.1021/acs.jpclett.9b00906] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Topological semimetals in ferromagnetic materials have attracted an enormous amount of attention due to potential applications in spintronics. Using first-principles density functional theory together with an effective lattice model, here we present a new family of topological semimetals with a fully spin-polarized nodal loop in alkaline metal monochalcogenide MX (M = Li, Na, K, Rb, or Cs; X = S, Se, or Te) monolayers. The half-metallic ferromagnetism can be established in MX monolayers, in which one nodal loop formed by two crossing bands with the same spin components is found at the Fermi energy. This nodal loop half-metal survives even when considering the spin-orbit coupling owing to the symmetry protection provided by the Mz mirror plane. The quantum anomalous Hall state and Weyl-like semimetal in this system can be also achieved by rotating the spin from the out-of-plane to the in-plane direction. The MX monolayers hosting rich topological phases thus offer an excellent platform for realizing advanced spintronic concepts.
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Affiliation(s)
- Xiaodong Zhou
- Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), Beijing Key Lab of Nanophotonics Ultrafine Optoelectronic Systems, and School of Physics , Beijing Institute of Technology , Beijing 100081 , China
| | - Run-Wu Zhang
- Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), Beijing Key Lab of Nanophotonics Ultrafine Optoelectronic Systems, and School of Physics , Beijing Institute of Technology , Beijing 100081 , China
| | - Zeying Zhang
- Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), Beijing Key Lab of Nanophotonics Ultrafine Optoelectronic Systems, and School of Physics , Beijing Institute of Technology , Beijing 100081 , China
| | - Da-Shuai Ma
- Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), Beijing Key Lab of Nanophotonics Ultrafine Optoelectronic Systems, and School of Physics , Beijing Institute of Technology , Beijing 100081 , China
| | - Wanxiang Feng
- Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), Beijing Key Lab of Nanophotonics Ultrafine Optoelectronic Systems, and School of Physics , Beijing Institute of Technology , Beijing 100081 , China
- Peter Grünberg Institut and Institute for Advanced Simulation , Forschungszentrum Jülich and JARA , D-52425 Jülich , Germany
| | - Yuriy Mokrousov
- Peter Grünberg Institut and Institute for Advanced Simulation , Forschungszentrum Jülich and JARA , D-52425 Jülich , Germany
- Institute of Physics , Johannes Gutenberg University Mainz , 55099 Mainz , Germany
| | - Yugui Yao
- Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), Beijing Key Lab of Nanophotonics Ultrafine Optoelectronic Systems, and School of Physics , Beijing Institute of Technology , Beijing 100081 , China
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25
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Hou Y, Wu R. Axion Insulator State in a Ferromagnet/Topological Insulator/Antiferromagnet Heterostructure. NANO LETTERS 2019; 19:2472-2477. [PMID: 30868887 DOI: 10.1021/acs.nanolett.9b00047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
We propose the use of ferromagnetic insulator MnBi2Se4/Bi2Se3/antiferromagnetic insulator Mn2Bi2Se5 heterostructures for the realization of the axion insulator state. Importantly, the axion insulator state in such heterostructures only depends on the magnetization of the ferromagnetic insulator and, hence, can be observed in a wide range of external magnetic fields. Using density functional calculations and model Hamiltonian simulations, we find that the top and bottom surfaces have opposite half-quantum Hall conductances, [Formula: see text] and [Formula: see text], with a sizable global spin gap of 5.1 meV opened for the topological surface states of Bi2Se3. Our work provides a new strategy for the search of axion insulators by using van der Waals antiferromagnetic insulators along with three-dimensional topological insulators.
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Affiliation(s)
- Yusheng Hou
- Department of Physics and Astronomy , University of California , Irvine , California 92697-4575 , United States
| | - Ruqian Wu
- Department of Physics and Astronomy , University of California , Irvine , California 92697-4575 , United States
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26
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Ultrafast manipulation of topologically enhanced surface transport driven by mid-infrared and terahertz pulses in Bi 2Se 3. Nat Commun 2019; 10:607. [PMID: 30723197 PMCID: PMC6363774 DOI: 10.1038/s41467-019-08559-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Accepted: 01/18/2019] [Indexed: 11/17/2022] Open
Abstract
Topology-protected surface transport of ultimate thinness in three-dimensional topological insulators (TIs) is breaking new ground in quantum science and technology. Yet a challenge remains on how to disentangle and selectively control surface helical spin transport from the bulk contribution. Here we use the mid-infrared and terahertz (THz) photoexcitation of exclusive intraband transitions to enable ultrafast manipulation of surface THz conductivity in Bi2Se3. The unique, transient electronic state is characterized by frequency-dependent carrier relaxations that directly distinguish the faster surface channel than the bulk with no complication from interband excitations or need for reduced bulk doping. We determine the topological enhancement ratio between bulk and surface scattering rates, i.e., γBS/γSS ~3.80 in equilibrium. The ultra-broadband, wavelength-selective pumping may be applied to emerging topological semimetals for separation and control of the protected transport connected with the Weyl nodes from other bulk bands. It remains challenging on how to selectively control terahertz conductivity at surface from the bulk contribution in topological insulators. Here, Luo et al. discover and manipulate topologically enhanced surface transport due to helical spin structure using mid-infrared and terahertz ultrafast photoexcitations.
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27
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Xiao D, Jiang J, Shin JH, Wang W, Wang F, Zhao YF, Liu C, Wu W, Chan MHW, Samarth N, Chang CZ. Realization of the Axion Insulator State in Quantum Anomalous Hall Sandwich Heterostructures. PHYSICAL REVIEW LETTERS 2018; 120:056801. [PMID: 29481164 DOI: 10.1103/physrevlett.120.056801] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Revised: 11/28/2017] [Indexed: 05/23/2023]
Abstract
The "magnetoelectric effect" arises from the coupling between magnetic and electric properties in materials. The Z_{2} invariant of topological insulators (TIs) leads to a quantized version of this phenomenon, known as the topological magnetoelectric (TME) effect. This effect can be realized in a new topological phase called an "axion insulator" whose surface states are all gapped but the interior still obeys time reversal symmetry. We demonstrate such a phase using electrical transport measurements in a quantum anomalous Hall (QAH) sandwich heterostructure, in which two compositionally different magnetic TI layers are separated by an undoped TI layer. Magnetic force microscopy images of the same sample reveal sequential magnetization reversals of the top and bottom layers at different coercive fields, a consequence of the weak interlayer exchange coupling due to the spacer. When the magnetization is antiparallel, both the Hall resistance and Hall conductance show zero plateaus, accompanied by a large longitudinal resistance and vanishing longitudinal conductance, indicating the realization of an axion insulator state. Our findings thus show evidence for a phase of matter distinct from the established QAH state and provide a promising platform for the realization of the TME effect.
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Affiliation(s)
- Di Xiao
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Jue Jiang
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Jae-Ho Shin
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Wenbo Wang
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Fei Wang
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Yi-Fan Zhao
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Chaoxing Liu
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Weida Wu
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Moses H W Chan
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Nitin Samarth
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Cui-Zu Chang
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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28
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Wang J, Zhang SC. Topological states of condensed matter. NATURE MATERIALS 2017; 16:1062-1067. [PMID: 29066825 DOI: 10.1038/nmat5012] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2017] [Accepted: 09/24/2017] [Indexed: 06/07/2023]
Abstract
Topological states of quantum matter have been investigated intensively in recent years in materials science and condensed matter physics. The field developed explosively largely because of the precise theoretical predictions, well-controlled materials processing, and novel characterization techniques. In this Perspective, we review recent progress in topological insulators, the quantum anomalous Hall effect, chiral topological superconductors, helical topological superconductors and Weyl semimetals.
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Affiliation(s)
- Jing Wang
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - Shou-Cheng Zhang
- Department of Physics, McCullough Building, Stanford University, Stanford, California 94305-4045, USA
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29
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Mogi M, Kawamura M, Tsukazaki A, Yoshimi R, Takahashi KS, Kawasaki M, Tokura Y. Tailoring tricolor structure of magnetic topological insulator for robust axion insulator. SCIENCE ADVANCES 2017; 3:eaao1669. [PMID: 28989967 PMCID: PMC5630236 DOI: 10.1126/sciadv.aao1669] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 09/15/2017] [Indexed: 05/23/2023]
Abstract
Exploration of novel electromagnetic phenomena is a subject of great interest in topological quantum materials. One of the unprecedented effects to be experimentally verified is the topological magnetoelectric (TME) effect originating from an unusual coupling of electric and magnetic fields in materials. A magnetic heterostructure of topological insulator (TI) hosts such exotic magnetoelectric coupling and can be expected to realize the TME effect as an axion insulator. We designed a magnetic TI with a tricolor structure where a nonmagnetic layer of (Bi, Sb)2Te3 is sandwiched by a soft ferromagnetic Cr-doped (Bi, Sb)2Te3 and a hard ferromagnetic V-doped (Bi, Sb)2Te3. Accompanied by the quantum anomalous Hall (QAH) effect, we observe zero Hall conductivity plateaus, which are a hallmark of the axion insulator state, in a wide range of magnetic fields between the coercive fields of Cr- and V-doped layers. The resistance of the axion insulator state reaches as high as 109 ohms, leading to a gigantic magnetoresistance ratio exceeding 10,000,000% upon the transition from the QAH state. The tricolor structure of the TI may not only be an ideal arena for the topologically distinct phenomena but can also provide magnetoresistive applications for advancing dissipation-less topological electronics.
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Affiliation(s)
- Masataka Mogi
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Minoru Kawamura
- RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan
| | - Atsushi Tsukazaki
- Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577, Japan
| | - Ryutaro Yoshimi
- RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan
| | - Kei S. Takahashi
- RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan
- PRESTO, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0075, Japan
| | - Masashi Kawasaki
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan
| | - Yoshinori Tokura
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan
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30
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Kurumaji T, Takahashi Y, Fujioka J, Masuda R, Shishikura H, Ishiwata S, Tokura Y. Optical Magnetoelectric Resonance in a Polar Magnet (Fe,Zn)_{2}Mo_{3}O_{8} with Axion-Type Coupling. PHYSICAL REVIEW LETTERS 2017; 119:077206. [PMID: 28949678 DOI: 10.1103/physrevlett.119.077206] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2017] [Indexed: 06/07/2023]
Abstract
We report the polarization rotation of terahertz light resonant with the magnetoelectric (ME) spin excitation in the multiferroic (Fe,Zn)_{2}Mo_{3}O_{8}. This resonance reflects the frequency dispersion of the diagonal ME susceptibility (axion term), with which we quantitatively reproduce the thermal and magnetic-field evolution of the observed polarization rotation spectra. The application of the sum rule on the extrapolated dc value of the spectral weight of the ME oscillator provides insight into the dc linear ME effect. The present finding highlights a novel optical functionality of spin excitations in multiferroics that originates from diagonal ME coupling.
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Affiliation(s)
- T Kurumaji
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - Y Takahashi
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
- PRESTO, Japan Science and Technology Agency, Chiyoda, Tokyo 102-8666, Japan
| | - J Fujioka
- Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - R Masuda
- Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - H Shishikura
- Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - S Ishiwata
- Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
- PRESTO, Japan Science and Technology Agency, Chiyoda, Tokyo 102-8666, Japan
| | - Y Tokura
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
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31
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Grauer S, Fijalkowski KM, Schreyeck S, Winnerlein M, Brunner K, Thomale R, Gould C, Molenkamp LW. Scaling of the Quantum Anomalous Hall Effect as an Indicator of Axion Electrodynamics. PHYSICAL REVIEW LETTERS 2017; 118:246801. [PMID: 28665643 DOI: 10.1103/physrevlett.118.246801] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Indexed: 06/07/2023]
Abstract
We report on the scaling behavior of V-doped (Bi,Sb)_{2}Te_{3} samples in the quantum anomalous Hall regime for samples of various thickness. While previous quantum anomalous Hall measurements showed the same scaling as expected from a two-dimensional integer quantum Hall state, we observe a dimensional crossover to three spatial dimensions as a function of layer thickness. In the limit of a sufficiently thick layer, we find scaling behavior matching the flow diagram of two parallel conducting topological surface states of a three-dimensional topological insulator each featuring a fractional shift of 1/2e^{2}/h in the flow diagram Hall conductivity, while we recover the expected integer quantum Hall behavior for thinner layers. This constitutes the observation of a distinct type of quantum anomalous Hall effect, resulting from 1/2e^{2}/h Hall conductance quantization of three-dimensional topological insulator surface states, in an experiment which does not require decomposition of the signal to separate the contribution of two surfaces. This provides a possible experimental link between quantum Hall physics and axion electrodynamics.
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Affiliation(s)
- S Grauer
- Faculty for Physics and Astronomy (EP3 and TP1), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - K M Fijalkowski
- Faculty for Physics and Astronomy (EP3 and TP1), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - S Schreyeck
- Faculty for Physics and Astronomy (EP3 and TP1), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - M Winnerlein
- Faculty for Physics and Astronomy (EP3 and TP1), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - K Brunner
- Faculty for Physics and Astronomy (EP3 and TP1), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - R Thomale
- Faculty for Physics and Astronomy (EP3 and TP1), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - C Gould
- Faculty for Physics and Astronomy (EP3 and TP1), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - L W Molenkamp
- Faculty for Physics and Astronomy (EP3 and TP1), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
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32
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Dziom V, Shuvaev A, Pimenov A, Astakhov GV, Ames C, Bendias K, Böttcher J, Tkachov G, Hankiewicz EM, Brüne C, Buhmann H, Molenkamp LW. Observation of the universal magnetoelectric effect in a 3D topological insulator. Nat Commun 2017; 8:15197. [PMID: 28504268 PMCID: PMC5440727 DOI: 10.1038/ncomms15197] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 03/06/2017] [Indexed: 12/17/2022] Open
Abstract
The electrodynamics of topological insulators (TIs) is described by modified Maxwell's equations, which contain additional terms that couple an electric field to a magnetization and a magnetic field to a polarization of the medium, such that the coupling coefficient is quantized in odd multiples of α/4π per surface. Here we report on the observation of this so-called topological magnetoelectric effect. We use monochromatic terahertz (THz) spectroscopy of TI structures equipped with a semitransparent gate to selectively address surface states. In high external magnetic fields, we observe a universal Faraday rotation angle equal to the fine structure constant α=e2/2hc (in SI units) when a linearly polarized THz radiation of a certain frequency passes through the two surfaces of a strained HgTe 3D TI. These experiments give insight into axion electrodynamics of TIs and may potentially be used for a metrological definition of the three basic physical constants.
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Affiliation(s)
- V. Dziom
- Institute of Solid State Physics, Viennta University of Technology, 1040 Vienna, Austria
| | - A. Shuvaev
- Institute of Solid State Physics, Viennta University of Technology, 1040 Vienna, Austria
| | - A. Pimenov
- Institute of Solid State Physics, Viennta University of Technology, 1040 Vienna, Austria
| | - G. V. Astakhov
- Physikalisches Institut (EP6), Universität Würzburg, 97074 Würzburg, Germany
| | - C. Ames
- Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany
| | - K. Bendias
- Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany
| | - J. Böttcher
- Institut für Theoretische Physik und Astronomie, Universität Würzburg, 97074 Würzburg, Germany
| | - G. Tkachov
- Institut für Theoretische Physik und Astronomie, Universität Würzburg, 97074 Würzburg, Germany
| | - E. M. Hankiewicz
- Institut für Theoretische Physik und Astronomie, Universität Würzburg, 97074 Würzburg, Germany
| | - C. Brüne
- Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany
| | - H. Buhmann
- Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany
| | - L. W. Molenkamp
- Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany
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33
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Crosse JA. Theory of topological insulator waveguides: polarization control and the enhancement of the magneto-electric effect. Sci Rep 2017; 7:43115. [PMID: 28220875 PMCID: PMC5318882 DOI: 10.1038/srep43115] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 01/19/2017] [Indexed: 12/03/2022] Open
Abstract
Topological insulators subject to a time-reversal-symmetry-breaking perturbation are predicted to display a magneto-electric effect that causes the electric and magnetic induction fields to mix at the material's surface. This effect induces polarization rotations of between ≈1-10 mrad per interface in an incident plane-polarized electromagnetic wave normal to a multilayered structure. Here we show, theoretically and numerically, that by using a waveguide geometry with a topological insulator guide layer and magneto-dielectric cladding it is possible to achieve rotations of ≈100 mrad and generate an elliptical polarization with only a three-layered structure. This geometry is beneficial, not only as a way to enhance the magneto-electric effect, rendering it easier to observe, but also as a method for controlling the polarization of electromagnetic radiation.
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Affiliation(s)
- J. A. Crosse
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3 117583, Singapore
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34
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Shao Y, Post KW, Wu JS, Dai S, Frenzel AJ, Richardella AR, Lee JS, Samarth N, Fogler MM, Balatsky AV, Kharzeev DE, Basov DN. Faraday Rotation Due to Surface States in the Topological Insulator (Bi 1-xSb x) 2Te 3. NANO LETTERS 2017; 17:980-984. [PMID: 28030948 DOI: 10.1021/acs.nanolett.6b04313] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Using magneto-infrared spectroscopy, we have explored the charge dynamics of (Bi,Sb)2Te3 thin films on InP substrates. From the magneto-transmission data we extracted three distinct cyclotron resonance (CR) energies that are all apparent in the broad band Faraday rotation (FR) spectra. This comprehensive FR-CR data set has allowed us to isolate the response of the bulk states from the intrinsic surface states associated with both the top and bottom surfaces of the film. The FR data uncovered that electron- and hole-type Dirac Fermions reside on opposite surfaces of our films, which paves the way for observing many exotic quantum phenomena in topological insulators.
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Affiliation(s)
- Yinming Shao
- Department of Physics, Columbia University , New York, New York 10027, United States
| | - Kirk W Post
- Physics Department, University of California-San Diego , La Jolla, California 92093, United States
| | - Jhih-Sheng Wu
- Physics Department, University of California-San Diego , La Jolla, California 92093, United States
| | - Siyuan Dai
- Physics Department, University of California-San Diego , La Jolla, California 92093, United States
| | - Alex J Frenzel
- Physics Department, University of California-San Diego , La Jolla, California 92093, United States
| | - Anthony R Richardella
- Department of Physics, The Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Joon Sue Lee
- Department of Physics, The Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Nitin Samarth
- Department of Physics, The Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Michael M Fogler
- Physics Department, University of California-San Diego , La Jolla, California 92093, United States
| | - Alexander V Balatsky
- Nordita, KTH Royal Institute of Technology and Stockholm University , Roslagstullsbacken 23, SE-106 91 Stockholm, Sweden
- Institute for Materials Science, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Dmitri E Kharzeev
- Department of Physics and Astronomy, Stony Brook University , Stony Brook, New York 11794-3800, United States
- Department of Physics and RIKEN-BNL Research Center, Brookhaven National Laboratory , Upton, New York 11973, United States
| | - D N Basov
- Department of Physics, Columbia University , New York, New York 10027, United States
- Physics Department, University of California-San Diego , La Jolla, California 92093, United States
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35
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Song JCW, Kats MA. Giant Hall Photoconductivity in Narrow-Gapped Dirac Materials. NANO LETTERS 2016; 16:7346-7351. [PMID: 27960456 DOI: 10.1021/acs.nanolett.6b02559] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Carrier dynamics acquire a new character in the presence of Bloch-band Berry curvature, which naturally arises in gapped Dirac materials (GDMs). Here, we argue that photoresponse in GDMs with small band gaps is dramatically enhanced by Berry curvature. This manifests in a giant and saturable Hall photoconductivity when illuminated by circularly polarized light. Unlike Hall motion arising from a Lorentz force in a magnetic field, which impedes longitudinal carrier motion, Hall photoconductivity arising from Berry curvature can boost longitudinal carrier transport. In GDMs, this results in a helicity-dependent photoresponse in the Hall regime, where photoconductivity is dominated by its Hall component. We find that the induced Hall conductivity per incident irradiance is enhanced by up to 6 orders of magnitude when moving from the visible regime (with corresponding band gaps) to the far infrared. These results suggest that narrow-gap GDMs are an ideal test-bed for the unique physics that arise in the presence of Berry curvature and open a new avenue for infrared and terahertz optoelectronics.
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Affiliation(s)
- Justin C W Song
- Institute of High Performance Computing, Agency for Science, Technology, and Research, Singapore 138632
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 637371
| | - Mikhail A Kats
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
- Department of Materials Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
- Department of Physics, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
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36
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Shuvaev A, Dziom V, Kvon ZD, Mikhailov NN, Pimenov A. Universal Faraday Rotation in HgTe Wells with Critical Thickness. PHYSICAL REVIEW LETTERS 2016; 117:117401. [PMID: 27661718 DOI: 10.1103/physrevlett.117.117401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Indexed: 06/06/2023]
Abstract
The universal value of the Faraday rotation angle close to the fine structure constant (α≈1/137) is experimentally observed in thin HgTe quantum wells with a thickness on the border between trivial insulating and the topologically nontrivial Dirac phases. The quantized value of the Faraday angle remains robust in the broad range of magnetic fields and gate voltages. Dynamic Hall conductivity of the holelike carriers extracted from the analysis of the transmission data shows a theoretically predicted universal value of σ_{xy}=e^{2}/h, which is consistent with the doubly degenerate Dirac state. On shifting the Fermi level by the gate voltage, the effective sign of the charge carriers changes from positive (holes) to negative (electrons). The electronlike part of the dynamic response does not show quantum plateaus and is well described within the classical Drude model.
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Affiliation(s)
- A Shuvaev
- Institute of Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria
| | - V Dziom
- Institute of Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria
| | - Z D Kvon
- Novosibirsk State University, Novosibirsk 630090, Russia
- Institute of Semiconductor Physics, Novosibirsk 630090, Russia
| | - N N Mikhailov
- Novosibirsk State University, Novosibirsk 630090, Russia
- Institute of Semiconductor Physics, Novosibirsk 630090, Russia
| | - A Pimenov
- Institute of Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria
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