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Gao Y, Zeng XY, Wang XB, Shi YG, Cheng L, Qi J. Terahertz manipulation of nonlinear optical response in topological material PtBi 2. OPTICS LETTERS 2024; 49:3862-3865. [PMID: 39008727 DOI: 10.1364/ol.525200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2024] [Accepted: 06/08/2024] [Indexed: 07/17/2024]
Abstract
The substantial nonlinear optical response observed in numerous topological materials renders them well-suited for optic and photonic applications, underscoring the critical need to devise effective strategies for manipulating their nonlinearity to enhance their versatility across different applications. In this Letter, we focus on the second-harmonic generation (SHG) response of the topological material PtBi2 under intense terahertz (THz) pulses and unveil the transient nonlinearity manipulated by a THz electric field. Our findings demonstrate that upon excitation of an intense THz pulse, there emerges a substantial enhancement in the SHG signal of PtBi2, which is predominantly attributed to the linear term involving the THz field, i.e., χ(2)χ(3)ETHz. We also clearly observe the transient change in the nonlinear coefficients, which could arise from the excitation of the bands with linear dispersion via the intense THz pulse. These findings bear significant implications for achieving ultrafast modulation of nonlinearity in topological materials, thereby opening avenues for advanced applications in this field.
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Zeng Z, Tian Z, Wang Y, Ge C, Strauß F, Braun K, Michel P, Huang L, Liu G, Li D, Scheele M, Chen M, Pan A, Wang X. Dual polarization-enabled ultrafast bulk photovoltaic response in van der Waals heterostructures. Nat Commun 2024; 15:5355. [PMID: 38918419 PMCID: PMC11199638 DOI: 10.1038/s41467-024-49760-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Accepted: 06/19/2024] [Indexed: 06/27/2024] Open
Abstract
The bulk photovoltaic effect (BPVE) originating from spontaneous charge polarizations can reach high conversion efficiency exceeding the Shockley-Queisser limit. Emerging van der Waals (vdW) heterostructures provide the ideal platform for BPVE due to interfacial interactions naturally breaking the crystal symmetries of the individual constituents and thus inducing charge polarizations. Here, we show an approach to obtain ultrafast BPVE by taking advantage of dual interfacial polarizations in vdW heterostructures. While the in-plane polarization gives rise to the BPVE in the overlayer, the charge carrier transfer assisted by the out-of-plane polarization further accelerates the interlayer electronic transport and enhances the BPVE. We illustrate the concept in MoS2/black phosphorus heterostructures, where the experimentally observed intrinsic BPVE response time achieves 26 ps, orders of magnitude faster than that of conventional non-centrosymmetric materials. Moreover, the heterostructure device possesses an extrinsic response time of approximately 2.2 ns and a bulk photovoltaic coefficient of 0.6 V-1, which is among the highest values for vdW BPV devices reported so far. Our study thus points to an effective way of designing ultrafast BPVE for high-speed photodetection.
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Grants
- the National Key Research and Development Program of Ministry of Science and Technology (Nos. 2022YFA1204300), the National Natural Science Foundation of China (Nos. 52022029, 52302175, 52221001, U23A20570, 92263107, 62090035, 12174098), the Hunan Provincial Natural Science Foundation of China (Nos. 2023JJ40138, 2022JJ30142),
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Affiliation(s)
- Zhouxiaosong Zeng
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, 410082, China
- School of Physics and Electronics, Hunan University, Changsha, 410082, China
- Institute of Physical and Theoretical Chemistry and LISA, University of Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
| | - Zhiqiang Tian
- Key Laboratory for Matter Microstructure and Function of Hunan Province, Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, Synergetic Innovation Center for Quantum Effects and Applications (SICQEA), School of Physics and Electronics, Hunan Normal University, Changsha, 410081, China
| | - Yufan Wang
- School of Physics and Electronics, Hunan University, Changsha, 410082, China
| | - Cuihuan Ge
- School of Physics and Electronics, Hunan University, Changsha, 410082, China
| | - Fabian Strauß
- Institute of Physical and Theoretical Chemistry and LISA, University of Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
| | - Kai Braun
- Institute of Physical and Theoretical Chemistry and LISA, University of Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
| | - Patrick Michel
- Institute of Physical and Theoretical Chemistry and LISA, University of Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
| | - Lanyu Huang
- School of Physics and Electronics, Hunan University, Changsha, 410082, China
| | - Guixian Liu
- School of Physics and Electronics, Hunan University, Changsha, 410082, China
| | - Dong Li
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, 410082, China
| | - Marcus Scheele
- Institute of Physical and Theoretical Chemistry and LISA, University of Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
| | - Mingxing Chen
- Key Laboratory for Matter Microstructure and Function of Hunan Province, Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, Synergetic Innovation Center for Quantum Effects and Applications (SICQEA), School of Physics and Electronics, Hunan Normal University, Changsha, 410081, China.
- State Key Laboratory of Powder Metallurgy, Central South University, Changsha, 410083, China.
| | - Anlian Pan
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, 410082, China.
- Key Laboratory for Matter Microstructure and Function of Hunan Province, Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, Synergetic Innovation Center for Quantum Effects and Applications (SICQEA), School of Physics and Electronics, Hunan Normal University, Changsha, 410081, China.
| | - Xiao Wang
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, 410082, China.
- School of Physics and Electronics, Hunan University, Changsha, 410082, China.
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3
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Ji Z, Song Y, Song Y, Li Z, Zhang J, Lou S, Zhang Z, Jin Q. Temperature-Dependent Spin-to-Charge Conversion and Efficient Manipulation of Elliptical THz Waves in Bi 2Te 3/TbFeCo Heterostructures. ACS APPLIED MATERIALS & INTERFACES 2024. [PMID: 38656108 DOI: 10.1021/acsami.4c02263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Topological insulators (TIs) with spin-momentum-locked surface states and considerable spin-to-charge conversion (SCC) efficiency are ideal substitutes for the nonmagnetic layer in the traditional ferromagnetic/nonmagnetic (FM/NM) spintronic terahertz (THz) emitters. Here, the TI/ferrimagnetic structure as an effective polarization tunable THz source is verified by terahertz emission spectroscopy. The emitted THz electric field can be separated into two THz components utilizing their opposite symmetry on pump polarization and the magnetic field. TI not only emits a THz electric field via the linear photogalvanic effect (LPGE) but also serves as the medium of SCC via the inverse Edelstein effect (IEE) in the heterostructure. In addition, the amplitude and polarity of the SCC component can be efficiently manipulated by temperature in our ferrimagnetic TbFeCo layer compared with Co or Fe. Once these two THz components are delicately set orthogonally, an elliptical THz wave is generated by the intrinsic phase difference at the THz frequency range. The feasible control of its polarization and chirality is demonstrated by three means: pump polarization, magnetic field, and temperature. These appealing observations may pave the way for the development of elliptical THz wave emitters and polarization-sensitive THz spectroscopy.
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Affiliation(s)
- Zhihao Ji
- Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Laboratory of Micro and Nano Photonic Structures (MOE), Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
| | - Yuna Song
- Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Laboratory of Micro and Nano Photonic Structures (MOE), Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
| | - Yiwen Song
- Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Laboratory of Micro and Nano Photonic Structures (MOE), Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
| | - Ziyang Li
- Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Laboratory of Micro and Nano Photonic Structures (MOE), Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
| | - Jingying Zhang
- Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Laboratory of Micro and Nano Photonic Structures (MOE), Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
| | - Shitao Lou
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Zongzhi Zhang
- Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Laboratory of Micro and Nano Photonic Structures (MOE), Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
| | - Qingyuan Jin
- Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Laboratory of Micro and Nano Photonic Structures (MOE), Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
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4
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Chen Z, Qiu H, Cheng X, Cui J, Jin Z, Tian D, Zhang X, Xu K, Liu R, Niu W, Zhou L, Qiu T, Chen Y, Zhang C, Xi X, Song F, Yu R, Zhai X, Jin B, Zhang R, Wang X. Defect-induced helicity dependent terahertz emission in Dirac semimetal PtTe 2 thin films. Nat Commun 2024; 15:2605. [PMID: 38521797 PMCID: PMC10960839 DOI: 10.1038/s41467-024-46821-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2024] [Accepted: 03/12/2024] [Indexed: 03/25/2024] Open
Abstract
Nonlinear transport enabled by symmetry breaking in quantum materials has aroused considerable interest in condensed matter physics and interdisciplinary electronics. However, achieving a nonlinear optical response in centrosymmetric Dirac semimetals via defect engineering has remained a challenge. Here, we observe the helicity dependent terahertz emission in Dirac semimetal PtTe2 thin films via the circular photogalvanic effect under normal incidence. This is activated by a controllable out-of-plane Te-vacancy defect gradient, which we unambiguously evidence with electron ptychography. The defect gradient lowers the symmetry, which not only induces the band spin splitting but also generates the giant Berry curvature dipole responsible for the circular photogalvanic effect. We demonstrate that the THz emission can be manipulated by the Te-vacancy defect concentration. Furthermore, the temperature evolution of the THz emission features a minimum in the THz amplitude due to carrier compensation. Our work provides a universal strategy for symmetry breaking in centrosymmetric Dirac materials for efficient nonlinear transport.
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Affiliation(s)
- Zhongqiang Chen
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, State Key Laboratory of Spintronics Devices and Technologies, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Hongsong Qiu
- Research Institute of Superconductor Electronics, School of Electronic Science and Engineering, MOE Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances, Nanjing University, 210093, Nanjing, China
| | - Xinjuan Cheng
- Department of Applied Physics, MIIT Key Laboratory of Semiconductor Microstructures and Quantum Sensing, Nanjing University of Science and Technology, 210094, Nanjing, China
| | - Jizhe Cui
- School of Materials Science and Engineering, Tsinghua University, 100084, Beijing, China
| | - Zuanming Jin
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, University of Shanghai for Science and Technology, 200093, Shanghai, China
| | - Da Tian
- Research Institute of Superconductor Electronics, School of Electronic Science and Engineering, MOE Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances, Nanjing University, 210093, Nanjing, China
| | - Xu Zhang
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, State Key Laboratory of Spintronics Devices and Technologies, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Kankan Xu
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, State Key Laboratory of Spintronics Devices and Technologies, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Ruxin Liu
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, State Key Laboratory of Spintronics Devices and Technologies, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Wei Niu
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, State Key Laboratory of Spintronics Devices and Technologies, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Liqi Zhou
- College of Engineering and Applied Sciences, Nanjing University, 210093, Nanjing, China
| | - Tianyu Qiu
- State Key Laboratory of Solid State Microstructures, School of Physics, Nanjing University, 210093, Nanjing, China
| | - Yequan Chen
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, State Key Laboratory of Spintronics Devices and Technologies, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Caihong Zhang
- Research Institute of Superconductor Electronics, School of Electronic Science and Engineering, MOE Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances, Nanjing University, 210093, Nanjing, China
| | - Xiaoxiang Xi
- State Key Laboratory of Solid State Microstructures, School of Physics, Nanjing University, 210093, Nanjing, China
| | - Fengqi Song
- State Key Laboratory of Solid State Microstructures, School of Physics, Nanjing University, 210093, Nanjing, China
| | - Rong Yu
- School of Materials Science and Engineering, Tsinghua University, 100084, Beijing, China
| | - Xuechao Zhai
- Department of Applied Physics, MIIT Key Laboratory of Semiconductor Microstructures and Quantum Sensing, Nanjing University of Science and Technology, 210094, Nanjing, China.
| | - Biaobing Jin
- Research Institute of Superconductor Electronics, School of Electronic Science and Engineering, MOE Key Laboratory of Optoelectronic Devices and Systems with Extreme Performances, Nanjing University, 210093, Nanjing, China.
- Purple Mountain Laboratories, 211111, Nanjing, China.
| | - Rong Zhang
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, State Key Laboratory of Spintronics Devices and Technologies, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, Nanjing, China.
- Department of Physics, Xiamen University, 361005, Xiamen, China.
| | - Xuefeng Wang
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, State Key Laboratory of Spintronics Devices and Technologies, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, Nanjing, China.
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5
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Kumi M, Wang T, Ejeromedoghene O, Wang J, Li P, Huang W. Exploring the Potentials of Chitin and Chitosan-Based Bioinks for 3D-Printing of Flexible Electronics: The Future of Sustainable Bioelectronics. SMALL METHODS 2024:e2301341. [PMID: 38403854 DOI: 10.1002/smtd.202301341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Indexed: 02/27/2024]
Abstract
Chitin and chitosan-based bioink for 3D-printed flexible electronics have tremendous potential for innovation in healthcare, agriculture, the environment, and industry. This biomaterial is suitable for 3D printing because it is highly stretchable, super-flexible, affordable, ultrathin, and lightweight. Owing to its ease of use, on-demand manufacturing, accurate and regulated deposition, and versatility with flexible and soft functional materials, 3D printing has revolutionized free-form construction and end-user customization. This study examined the potential of employing chitin and chitosan-based bioinks to build 3D-printed flexible electronic devices and optimize bioink formulation, printing parameters, and postprocessing processes to improve mechanical and electrical properties. The exploration of 3D-printed chitin and chitosan-based flexible bioelectronics will open new avenues for new flexible materials for numerous industrial applications.
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Affiliation(s)
- Moses Kumi
- Frontiers Science Center for Flexible Electronics (FSCFE), Xi'an Institute of Flexible Electronics (IFE), Xi'an Institute of Biomedical Materials and Engineering (IBME), Northwestern Polytechnical University (NPU), 127 West Youyi Road, Xi'an, Shaanxi, 710072, P. R. China
| | - Tengjiao Wang
- Frontiers Science Center for Flexible Electronics (FSCFE), Xi'an Institute of Flexible Electronics (IFE), Xi'an Institute of Biomedical Materials and Engineering (IBME), Northwestern Polytechnical University (NPU), 127 West Youyi Road, Xi'an, Shaanxi, 710072, P. R. China
| | - Onome Ejeromedoghene
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
| | - Junjie Wang
- Frontiers Science Center for Flexible Electronics (FSCFE), Xi'an Institute of Flexible Electronics (IFE), Xi'an Institute of Biomedical Materials and Engineering (IBME), Northwestern Polytechnical University (NPU), 127 West Youyi Road, Xi'an, Shaanxi, 710072, P. R. China
| | - Peng Li
- Frontiers Science Center for Flexible Electronics (FSCFE), Xi'an Institute of Flexible Electronics (IFE), Xi'an Institute of Biomedical Materials and Engineering (IBME), Northwestern Polytechnical University (NPU), 127 West Youyi Road, Xi'an, Shaanxi, 710072, P. R. China
| | - Wei Huang
- Frontiers Science Center for Flexible Electronics (FSCFE), Xi'an Institute of Flexible Electronics (IFE), Xi'an Institute of Biomedical Materials and Engineering (IBME), Northwestern Polytechnical University (NPU), 127 West Youyi Road, Xi'an, Shaanxi, 710072, P. R. China
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6
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Connelly BC, Taylor PJ, de Coster GJ. Emergence of threefold symmetric helical photocurrents in epitaxial low twinned Bi 2Se 3. Proc Natl Acad Sci U S A 2024; 121:e2307425121. [PMID: 38271339 PMCID: PMC10835140 DOI: 10.1073/pnas.2307425121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Accepted: 11/29/2023] [Indexed: 01/27/2024] Open
Abstract
We present evidence of a strong circular photon drag effect (PDE) in topological insulators (TIs) through the observation of helicity-dependent topological photocurrents with threefold rotational symmetry using THz spectroscopy in epitaxially-grown Bi2Se3 with reduced crystallographic twinning. We establish how twinned domains introduce competing nonlinear optical (NLO) responses inherent to the crystal structure that obscure geometry-sensitive optical processes through the introduction of a spurious mirror symmetry. Minimizing the twinning defect reveals strong NLO response currents whose magnitude and direction depend on the alignment of the excitation to the crystal axes and follow the threefold rotational symmetry of the crystal. Notably, photocurrents arising from helical light reverse direction for left/right circular polarizations and maintain a strong azimuthal dependence-a result uniquely attributable to the circular PDE, where the photon momentum acts as an applied in-plane field stationary in the laboratory frame. Our results demonstrate new levels of control over the magnitude and direction of photocurrents in TIs and that the study of single-domain films is crucial to reveal hidden phenomena that couple topological order and crystal symmetries.
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Affiliation(s)
- Blair C. Connelly
- U.S. Army Combat Capabilities Development Command Army Research Laboratory, Adelphi, MD20783
| | - Patrick J. Taylor
- U.S. Army Combat Capabilities Development Command Army Research Laboratory, Adelphi, MD20783
| | - George J. de Coster
- U.S. Army Combat Capabilities Development Command Army Research Laboratory, Adelphi, MD20783
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7
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You JY, Su G, Feng YP. A versatile model with three-dimensional triangular lattice for unconventional transport and various topological effects. Natl Sci Rev 2024; 11:nwad114. [PMID: 38116092 PMCID: PMC10727845 DOI: 10.1093/nsr/nwad114] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 02/18/2023] [Accepted: 03/02/2023] [Indexed: 12/21/2023] Open
Abstract
The finite Berry curvature in topological materials can induce many subtle phenomena, such as the anomalous Hall effect (AHE), spin Hall effect (SHE), anomalous Nernst effect (ANE), non-linear Hall effect (NLHE) and bulk photovoltaic effects. To explore these novel physics as well as their connection and coupling, a precise and effective model should be developed. Here, we propose such a versatile model-a 3D triangular lattice with alternating hopping parameters, which can yield various topological phases, including kagome bands, triply degenerate fermions, double Weyl semimetals and so on. We reveal that this special lattice can present unconventional transport due to its unique topological surface states and the aforementioned topological phenomena, such as AHE, ANE, NLHE and the topological photocurrent effect. In addition, we also provide a number of material candidates that have been synthesized experimentally with this lattice, and discuss two materials, including a non-magnetic triangular system for SHE, NLHE and the shift current, and a ferromagnetic triangular lattice for AHE and ANE. Our work provides an excellent platform, including both the model and materials, for the study of Berry-curvature-related physics.
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Affiliation(s)
- Jing-Yang You
- Department of Physics, National University of Singapore, Singapore 117551, Singapore
| | - Gang Su
- Kavli Institute for Theoretical Sciences, and CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Yuan Ping Feng
- Department of Physics, National University of Singapore, Singapore 117551, Singapore
- Centre for Advanced 2D Materials, National University of Singapore, Singapore 117546, Singapore
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8
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Seifert TS, Go D, Hayashi H, Rouzegar R, Freimuth F, Ando K, Mokrousov Y, Kampfrath T. Time-domain observation of ballistic orbital-angular-momentum currents with giant relaxation length in tungsten. NATURE NANOTECHNOLOGY 2023; 18:1132-1138. [PMID: 37550573 PMCID: PMC10575790 DOI: 10.1038/s41565-023-01470-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 06/29/2023] [Indexed: 08/09/2023]
Abstract
The emerging field of orbitronics exploits the electron orbital momentum L. Compared to spin-polarized electrons, L may allow the transfer of magnetic information with considerably higher density over longer distances in more materials. However, direct experimental observation of L currents, their extended propagation lengths and their conversion into charge currents has remained challenging. Here, we optically trigger ultrafast angular-momentum transport in Ni|W|SiO2 thin-film stacks. The resulting terahertz charge-current bursts exhibit a marked delay and width that grow linearly with the W thickness. We consistently ascribe these observations to a ballistic L current from Ni through W with a giant decay length (~80 nm) and low velocity (~0.1 nm fs-1). At the W/SiO2 interface, the L flow is efficiently converted into a charge current by the inverse orbital Rashba-Edelstein effect, consistent with ab initio calculations. Our findings establish orbitronic materials with long-distance ballistic L transport as possible candidates for future ultrafast devices and an approach to discriminate Hall-like and Rashba-Edelstein-like conversion processes.
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Affiliation(s)
- Tom S Seifert
- Department of Physics, Freie Universität Berlin, Berlin, Germany.
- Department of Physical Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany.
| | - Dongwook Go
- Peter-Grünberg-Institut, Forschungszentrum Jülich, Jülich, Germany
- Institute of Physics, Johannes-Gutenberg-Universität Mainz, Mainz, Germany
| | - Hiroki Hayashi
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama, Japan
- Keio Institute of Pure and Applied Sciences, Keio University, Yokohama, Japan
| | - Reza Rouzegar
- Department of Physics, Freie Universität Berlin, Berlin, Germany
- Department of Physical Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
| | - Frank Freimuth
- Peter-Grünberg-Institut, Forschungszentrum Jülich, Jülich, Germany
- Keio Institute of Pure and Applied Sciences, Keio University, Yokohama, Japan
| | - Kazuya Ando
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama, Japan
- Keio Institute of Pure and Applied Sciences, Keio University, Yokohama, Japan
- Center for Spintronics Research Network, Keio University, Yokohama, Japan
| | - Yuriy Mokrousov
- Peter-Grünberg-Institut, Forschungszentrum Jülich, Jülich, Germany
- Institute of Physics, Johannes-Gutenberg-Universität Mainz, Mainz, Germany
| | - Tobias Kampfrath
- Department of Physics, Freie Universität Berlin, Berlin, Germany
- Department of Physical Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
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9
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Shekhar S, Oh Y, Jeong JY, Choi Y, Cho D, Hong S. Nanoscale mapping of edge-state conductivity and charge-trap activity in topological insulators. MATERIALS HORIZONS 2023; 10:2245-2253. [PMID: 37014136 DOI: 10.1039/d2mh01259f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report the nanoscale mapping of topological edge-state conductivity and the effects of charge-traps on conductivity in a Bi2Se3 multilayer film under ambient conditions. In this strategy, we applied an electric field perpendicular to the surface plane of Bi2Se3via a conducting probe to directly map the charge-trap densities and conductivities with a nanoscale resolution. The results showed that edge regions had one-dimensional characteristics with higher conductivities (two orders) and lower charge-trap densities (four orders) than those of flat surface regions where their conductivities and charge-traps were dominated by bulk effects. Additionally, edges showed an enhanced conductivity with an elevated electric field, possibly due to the creation of new topological states by stronger spin-Hall effects. Importantly, we observed ultra-high photoconductivity predominantly on edge regions compared with that of flat surface regions, which was attributed to the excitation of edge-state carriers by light. Since our method provides an important insight into the charge transport in topological insulators, it could be a significant advancement in the development of error-tolerant topotronic devices.
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Affiliation(s)
- Shashank Shekhar
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea.
| | - Yuhyeon Oh
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea.
| | - Jin-Young Jeong
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea.
| | - Yoonji Choi
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea.
| | - Duckhyung Cho
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea.
| | - Seunghun Hong
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea.
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10
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Hou B, Wang D, Barker BA, Qiu DY. Exchange-Driven Intermixing of Bulk and Topological Surface States by Chiral Excitons in Bi_{2}Se_{3}. PHYSICAL REVIEW LETTERS 2023; 130:216402. [PMID: 37295093 DOI: 10.1103/physrevlett.130.216402] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 02/17/2023] [Accepted: 05/01/2023] [Indexed: 06/12/2023]
Abstract
Topological surface states (TSS) in the prototypical topological insulator (TI) Bi_{2}Se_{3} are frequently characterized using optical probes, but electron-hole interactions and their effect on surface localization and optical response of the TSS remain unexplored. Here, we use ab initio calculations to understand excitonic effects in the bulk and surface of Bi_{2}Se_{3}. We identify multiple series of chiral excitons that exhibit both bulk and TSS character, due to exchange-driven mixing. Our results address fundamental questions about the degree to which electron-hole interactions can relax the topological protection of surface states and dipole selection rules for circularly polarized light in TIs by elucidating the complex intermixture of bulk and surface states excited in optical measurements and their coupling to light.
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Affiliation(s)
- Bowen Hou
- Department of Mechanical Engineering and Material Sciences, Yale University, New Haven, Connecticut 06511, USA
| | - Dan Wang
- Department of Mechanical Engineering and Material Sciences, Yale University, New Haven, Connecticut 06511, USA
| | - Bradford A Barker
- Department of Physics, University of California, Merced, California 95343, USA
| | - Diana Y Qiu
- Department of Mechanical Engineering and Material Sciences, Yale University, New Haven, Connecticut 06511, USA
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11
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Polarization-controlled tunable directional spin-driven photocurrents in a magnetic metamaterial with threefold rotational symmetry. Nat Commun 2022; 13:6708. [PMID: 36344506 PMCID: PMC9640558 DOI: 10.1038/s41467-022-34374-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 10/21/2022] [Indexed: 11/09/2022] Open
Abstract
Future spintronics and quantum technologies will require a portfolio of techniques for manipulating electron spins in functional nanodevices. Especially, the establishment of the methods to control spin current is the key ingredient essential for the transfer and processing of information, enabling faster and low-energy operation. However, a universal method for manipulating spin currents with full-directional controllability and tunable magnitude has not been established. Here we show that an artificial material called a magnetic metamaterial (MM), which possesses a novel spintronic functionality not exhibited by the original substance, generates photo-driven ultrafast spin currents at room temperature via the magneto-photogalvanic effect. By tuning the polarization state of the excitation light, these spin currents can be directed with tunable magnitude along an arbitrary direction in the two-dimensional plane of the MM. This new concept may guide the design and creation of artificially engineered opto-spintronic functionalities beyond the limitations of conventional material science. By carefully structuring and patterning a material, it is possible to introduce emergent properties that would otherwise not exist. These metamaterials have allowed the development of a wide variety of new optical properties. Here, Matsubara et al present a magnetic metamaterial, where spin-currents can be directed by tuning the polarization of the incident light.
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12
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Gao Y, Pei Y, Xiang T, Cheng L, Qi J. Terahertz wave emission from the trigonal layered PtBi 2. iScience 2022; 25:104511. [PMID: 35720263 PMCID: PMC9204749 DOI: 10.1016/j.isci.2022.104511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Revised: 05/02/2022] [Accepted: 05/27/2022] [Indexed: 11/16/2022] Open
Abstract
In this work, broadband terahertz (THz) wave emissions have been detected from the trigonal layered PtBi2 on the excitation of the femtosecond laser pulses. Such THz generation is found to arise from the dominated linear photogalvanic effect, which is further discovered to strongly depend on the unique electronic structures of PtBi2. Furthermore, an effective nonlinear susceptibility of PtBi2 is also obtained and is nearly two orders of magnitude larger than that of the traditional nonlinear crystal for THz generation. Terahertz (THz) wave emission, topological semimetal, ultrafast photocurrent
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Affiliation(s)
- Yu Gao
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Yunhe Pei
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Tian Xiang
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Liang Cheng
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Jingbo Qi
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
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13
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Okamura Y, Morimoto T, Ogawa N, Kaneko Y, Guo GY, Nakamura M, Kawasaki M, Nagaosa N, Tokura Y, Takahashi Y. Photovoltaic effect by soft phonon excitation. Proc Natl Acad Sci U S A 2022; 119:e2122313119. [PMID: 35344426 PMCID: PMC9169116 DOI: 10.1073/pnas.2122313119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 02/20/2022] [Indexed: 11/22/2022] Open
Abstract
SignificanceThe quantum-mechanical geometric phase of electrons provides various phenomena such as the dissipationless photocurrent generation through the shift current mechanism. So far, the photocurrent generations are limited to above or near the band-gap photon energy, which contradicts the increasing demand of the low-energy photonic functionality. We demonstrate the photocurrent through the optical phonon excitations in ferroelectric BaTiO3 by using the terahertz light with photon energy far below the band gap. This photocurrent without electron-hole pair generation is never explained by the semiclassical treatment of electrons and only arises from the quantum-mechanical geometric phase. The observed photon-to-current conversion efficiency is as large as that for electronic excitation, which can be well accounted for by newly developed theoretical formulation of shift current.
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Affiliation(s)
- Yoshihiro Okamura
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
| | - Takahiro Morimoto
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
- PRESTO, Japan Science and Technology Agency, Tokyo 113-8656, Japan
| | - Naoki Ogawa
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
| | - Yoshio Kaneko
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
| | - Guang-Yu Guo
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
- Physics Division, National Center for Theoretical Sciences, Taipei 10617, Taiwan
| | - Masao Nakamura
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
| | - Masashi Kawasaki
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
| | - Naoto Nagaosa
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
| | - Yoshinori Tokura
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
- Tokyo College, University of Tokyo, Tokyo 113-8656, Japan
| | - Youtarou Takahashi
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
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14
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Ultrafast photothermoelectric effect in Dirac semimetallic Cd 3As 2 revealed by terahertz emission. Nat Commun 2022; 13:1623. [PMID: 35338125 PMCID: PMC8956572 DOI: 10.1038/s41467-022-29168-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 02/17/2022] [Indexed: 11/18/2022] Open
Abstract
The thermoelectric effects of topological semimetals have attracted tremendous research interest because many topological semimetals are excellent thermoelectric materials and thermoelectricity serves as one of their most important potential applications. In this work, we reveal the transient photothermoelectric response of Dirac semimetallic Cd3As2, namely the photo-Seebeck effect and photo-Nernst effect, by studying the terahertz (THz) emission from the transient photocurrent induced by these effects. Our excitation polarization and power dependence confirm that the observed THz emission is due to photothermoelectric effect instead of other nonlinear optical effect. Furthermore, when a weak magnetic field (~0.4 T) is applied, the response clearly indicates an order of magnitude enhancement on transient photothermoelectric current generation compared to the photo-Seebeck effect. Such enhancement supports an ambipolar transport nature of the photo-Nernst current generation in Cd3As2. These results highlight the enhancement of thermoelectric performance can be achieved in topological Dirac semimetals based on the Nernst effect, and our transient studies pave the way for thermoelectric devices applicable for high field circumstance when nonequilibrium state matters. The large THz emission due to highly efficient photothermoelectric conversion is comparable to conventional semiconductors through optical rectification and photo-Dember effect. Many topological semimetals are excellent thermoelectric materials, but previous studies were limited to steady-state properties. Here, the authors observe a transient thermoelectric response in Cd3As2 by detecting the resulting THz emission, with an enhanced response when a small magnetic field is applied.
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15
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Chen X, Wang H, Liu H, Wang C, Wei G, Fang C, Wang H, Geng C, Liu S, Li P, Yu H, Zhao W, Miao J, Li Y, Wang L, Nie T, Zhao J, Wu X. Generation and Control of Terahertz Spin Currents in Topology-Induced 2D Ferromagnetic Fe 3 GeTe 2 |Bi 2 Te 3 Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2106172. [PMID: 34816497 DOI: 10.1002/adma.202106172] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 11/10/2021] [Indexed: 06/13/2023]
Abstract
Future information technologies for low-dissipation quantum computation, high-speed storage, and on-chip communication applications require the development of atomically thin, ultracompact, and ultrafast spintronic devices in which information is encoded, stored, and processed using electron spin. Exploring low-dimensional magnetic materials, designing novel heterostructures, and generating and controlling ultrafast electron spin in 2D magnetism at room temperature, preferably in the unprecedented terahertz (THz) regime, is in high demand. Using THz emission spectroscopy driven by femtosecond laser pulses, optical THz spin-current bursts at room temperature in the 2D van der Waals ferromagnetic Fe3 GeTe2 (FGT) integrated with Bi2 Te3 as a topological insulator are successfully realized. The symmetry of the THz radiation is effectively controlled by the optical pumping incidence and external magnetic field directions, indicating that the THz generation mechanism is the inverse Edelstein effect contributed spin-to-charge conversion. Thickness-, temperature-, and structure-dependent nontrivial THz transients reveal that topology-enhanced interlayer exchange coupling increases the FGT Curie temperature to room temperature, which provides an effective approach for engineering THz spin-current pulses. These results contribute to the goal of all-optical generation, manipulation, and detection of ultrafast THz spin currents in room-temperature 2D magnetism, accelerating the development of atomically thin high-speed spintronic devices.
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Affiliation(s)
- Xinhou Chen
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Hangtian Wang
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Haijiang Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Chun Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Gaoshuai Wei
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chan Fang
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Hanchen Wang
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Chunyan Geng
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Shaojie Liu
- School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
| | - Peiyan Li
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Haiming Yu
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Weisheng Zhao
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China
| | - Jungang Miao
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Yutong Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
- Songshan Lake Materials Laboratory, Dongguan, 523808, China
| | - Li Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Tianxiao Nie
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China
| | - Jimin Zhao
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
- Songshan Lake Materials Laboratory, Dongguan, 523808, China
| | - Xiaojun Wu
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
- School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China
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16
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Kaner NT, Wei Y, Ying T, Xu X, Li W, Raza A, Li X, Yang J, Jiang Y, Tian WQ. Giant Shift Photovoltaic Current in Group V‐V Binary Nanosheets. ADVANCED THEORY AND SIMULATIONS 2022. [DOI: 10.1002/adts.202100472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - Yadong Wei
- School of Physics Harbin Institute of Technology Harbin 150001 China
| | - Tao Ying
- School of Physics Harbin Institute of Technology Harbin 150001 China
| | - Xiaodong Xu
- School of Physics Harbin Institute of Technology Harbin 150001 China
| | - Weiqi Li
- School of Physics Harbin Institute of Technology Harbin 150001 China
- State Key Laboratory of Intense Pulsed Radiation Simulation and Effect Xi'an 710024 China
| | - Ali Raza
- Department of Physics University of Sialkot (USKT) 1‐Km Main Daska Road Sialkot Punjab 51040 Pakistan
| | - Xingji Li
- School of Material Science and Engineering Harbin Institute of Technology Harbin 150001 China
| | - Jianqun Yang
- School of Material Science and Engineering Harbin Institute of Technology Harbin 150001 China
| | - YongYuan Jiang
- School of Physics Harbin Institute of Technology Harbin 150001 China
- Collaborative Innovation Center of Extreme Optics Shanxi University Taiyuan 030006 China
- Key Lab of Micro‐Optics and Photonic Technology of Heilongjiang Province Harbin 150001 China
| | - Wei Quan Tian
- Chongqing Key Laboratory of Theoretical and Computational Chemistry School of Chemistry and Chemical Engineering Chongqing University Chongqing 401331 China
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17
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Yoon HH, Ahmed F, Dai Y, Fernandez HA, Cui X, Bai X, Li D, Du M, Lipsanen H, Sun Z. Tunable Quantum Tunneling through a Graphene/Bi 2Se 3 Heterointerface for the Hybrid Photodetection Mechanism. ACS APPLIED MATERIALS & INTERFACES 2021; 13:58927-58935. [PMID: 34855351 PMCID: PMC8678989 DOI: 10.1021/acsami.1c18606] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Accepted: 11/23/2021] [Indexed: 06/13/2023]
Abstract
Graphene-based van der Waals heterostructures are promising building blocks for broadband photodetection because of the gapless nature of graphene. However, their performance is mostly limited by the inevitable trade-off between low dark current and photocurrent generation. Here, we demonstrate a hybrid photodetection mode based on the photogating effect coupled with the photovoltaic effect via tunable quantum tunneling through the unique graphene/Bi2Se3 heterointerface. The tunneling junction formed between the semimetallic graphene and the topologically insulating Bi2Se3 exhibits asymmetric rectifying and hysteretic current-voltage characteristics, which significantly suppresses the dark current and enhances the photocurrent. The photocurrent-to-dark current ratio increases by about a factor of 10 with the electrical tuning of tunneling resistance for efficient light detection covering the major photonic spectral band from the visible to the mid-infrared ranges. Our findings provide a novel concept of using tunable quantum tunneling for highly sensitive broadband photodetection in mixed-dimensional van der Waals heterostructures.
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Affiliation(s)
- Hoon Hahn Yoon
- Department
of Electronics and Nanoengineering, Aalto
University, FI-00076 Aalto, Finland
- QTF
Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland
| | - Faisal Ahmed
- Department
of Electronics and Nanoengineering, Aalto
University, FI-00076 Aalto, Finland
| | - Yunyun Dai
- Department
of Electronics and Nanoengineering, Aalto
University, FI-00076 Aalto, Finland
- QTF
Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland
| | - Henry A. Fernandez
- Department
of Electronics and Nanoengineering, Aalto
University, FI-00076 Aalto, Finland
- QTF
Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland
| | - Xiaoqi Cui
- Department
of Electronics and Nanoengineering, Aalto
University, FI-00076 Aalto, Finland
- QTF
Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland
| | - Xueyin Bai
- Department
of Electronics and Nanoengineering, Aalto
University, FI-00076 Aalto, Finland
- QTF
Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland
| | - Diao Li
- Department
of Electronics and Nanoengineering, Aalto
University, FI-00076 Aalto, Finland
- QTF
Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland
| | - Mingde Du
- Department
of Electronics and Nanoengineering, Aalto
University, FI-00076 Aalto, Finland
- QTF
Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland
| | - Harri Lipsanen
- Department
of Electronics and Nanoengineering, Aalto
University, FI-00076 Aalto, Finland
| | - Zhipei Sun
- Department
of Electronics and Nanoengineering, Aalto
University, FI-00076 Aalto, Finland
- QTF
Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland
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18
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Xi F, Yang H, Khayrudinov V, He Y, Haggren T, Zhou Y, Lipsanen H, Sun Z, Xu X. Enhanced terahertz emission from mushroom-shaped InAs nanowire network induced by linear and nonlinear optical effects. NANOTECHNOLOGY 2021; 33:085207. [PMID: 34768252 DOI: 10.1088/1361-6528/ac3948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2021] [Accepted: 11/12/2021] [Indexed: 06/13/2023]
Abstract
The development of powerful terahertz (THz) emitters is the cornerstone for future THz applications, such as communication, medical biology, non-destructive inspection, and scientific research. Here, we report the THz emission properties and mechanisms of mushroom-shaped InAs nanowire (NW) network using linearly polarized laser excitation. By investigating the dependence of THz signal to the incidence pump light properties (e.g. incident angle, direction, fluence, and polarization angle), we conclude that the THz wave emission from the InAs NW network is induced by the combination of linear and nonlinear optical effects. The former is a transient photocurrent accelerated by the photo-Dember field, while the latter is related to the resonant optical rectification effect. Moreover, thep-polarized THz wave emission component is governed by the linear optical effect with a proportion of ∼85% and the nonlinear optical effect of ∼15%. In comparison, thes-polarized THz wave emission component is mainly decided by the nonlinear optical effect. The THz emission is speculated to be enhanced by the localized surface plasmon resonance absorption of the In droplets on top of the NWs. This work verifies the nonlinear optical mechanism in the THz generation of semiconductor NWs and provides an enlightening reference for the structural design of powerful and flexible THz surface and interface emitters in transmission geometry.
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Affiliation(s)
- Fugang Xi
- Shaanxi Joint Lab of Graphene, State Key Laboratory of Photoelectric Technology and Functional Materials, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, Institute of Photonics & Photon-Technology, School of Physics, Northwest University, Xi'an 710127, People's Republic of China
| | - He Yang
- School of Instrumentation and Optoelectronic Engineering, Beihang University, Beijing 100191, People's Republic of China
- Department of Electronics and Nanoengineering, Aalto University, Espoo, PO Box 13500, FI-00076, Finland
| | - Vladislav Khayrudinov
- Department of Electronics and Nanoengineering, Aalto University, Espoo, PO Box 13500, FI-00076, Finland
| | - Yuhang He
- Shaanxi Joint Lab of Graphene, State Key Laboratory of Photoelectric Technology and Functional Materials, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, Institute of Photonics & Photon-Technology, School of Physics, Northwest University, Xi'an 710127, People's Republic of China
| | - Tuomas Haggren
- Department of Electronics and Nanoengineering, Aalto University, Espoo, PO Box 13500, FI-00076, Finland
| | - Yixuan Zhou
- Shaanxi Joint Lab of Graphene, State Key Laboratory of Photoelectric Technology and Functional Materials, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, Institute of Photonics & Photon-Technology, School of Physics, Northwest University, Xi'an 710127, People's Republic of China
| | - Harri Lipsanen
- Department of Electronics and Nanoengineering, Aalto University, Espoo, PO Box 13500, FI-00076, Finland
| | - Zhipei Sun
- Department of Electronics and Nanoengineering, Aalto University, Espoo, PO Box 13500, FI-00076, Finland
| | - Xinlong Xu
- Shaanxi Joint Lab of Graphene, State Key Laboratory of Photoelectric Technology and Functional Materials, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, Institute of Photonics & Photon-Technology, School of Physics, Northwest University, Xi'an 710127, People's Republic of China
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19
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Lee K, Lee DK, Yang D, Mishra R, Kim DJ, Liu S, Xiong Q, Kim SK, Lee KJ, Yang H. Superluminal-like magnon propagation in antiferromagnetic NiO at nanoscale distances. NATURE NANOTECHNOLOGY 2021; 16:1337-1341. [PMID: 34697489 DOI: 10.1038/s41565-021-00983-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 08/11/2021] [Indexed: 06/13/2023]
Abstract
Magnon-mediated angular-momentum flow in antiferromagnets may become a design element for energy-efficient, low-dissipation and high-speed spintronic devices1,2. Owing to their low energy dissipation, antiferromagnetic magnons can propagate over micrometre distances3. However, direct observation of their high-speed propagation has been elusive due to the lack of sufficiently fast probes2. Here we measure the antiferromagnetic magnon propagation in the time domain at the nanoscale (≤50 nm) with optical-driven terahertz emission. In non-magnetic-Bi2Te3/antiferromagnetic-insulator-NiO/ferromagnetic-Co trilayers, we observe a magnon velocity of ~650 km s-1 in the NiO layer. This velocity far exceeds previous estimations of the maximum magnon group velocity of ~40 km s-1, which were based on the magnon dispersion measurements of NiO using inelastic neutron scattering4,5. Our theory suggests that for magnon propagation at the nanoscale, a finite damping makes the dispersion anomalous for small magnon wavenumbers and yields a superluminal-like magnon velocity. Given the generality of finite dissipation in materials, our results strengthen the prospects of ultrafast nanodevices using antiferromagnetic magnons.
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Affiliation(s)
- Kyusup Lee
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore
| | - Dong-Kyu Lee
- Department of Materials Science and Engineering, Korea University, Seoul, Korea
| | - Dongsheng Yang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore
| | - Rahul Mishra
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore
- Centre for Applied Research in Electronics, Indian Institute of Technology Delhi, New Delhi, India
| | - Dong-Jun Kim
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore
| | - Sheng Liu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Qihua Xiong
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, P. R. China
- Beijing Academy of Quantum Information Sciences, Beijing, P. R. China
- Beijing Innovation Center for Future Chips, Tsinghua University, Beijing, P. R. China
| | - Se Kwon Kim
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
| | - Kyung-Jin Lee
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea.
| | - Hyunsoo Yang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore.
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20
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Mooshammer F, Plankl M, Siday T, Zizlsperger M, Sandner F, Vitalone R, Jing R, Huber MA, Basov DN, Huber R. Quantitative terahertz emission nanoscopy with multiresonant near-field probes. OPTICS LETTERS 2021; 46:3572-3575. [PMID: 34329227 DOI: 10.1364/ol.430400] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 06/28/2021] [Indexed: 06/13/2023]
Abstract
By sampling terahertz waveforms emitted from InAs surfaces, we reveal how the entire, realistic geometry of typical near-field probes drastically impacts the broadband electromagnetic fields. In the time domain, these modifications manifest as a shift in the carrier-envelope phase and emergence of a replica pulse with a time delay dictated by the length of the cantilever. This interpretation is fully corroborated by quantitative simulations of terahertz emission nanoscopy based on the finite element method. Our approach provides a solid theoretical framework for quantitative nanospectroscopy and sets the stage for a reliable description of subcycle, near-field microscopy at terahertz frequencies.
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21
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Devenson J, Norkus R, Juškėnas R, Krotkus A. Terahertz emission from ultrathin bismuth layers. OPTICS LETTERS 2021; 46:3681-3684. [PMID: 34329255 DOI: 10.1364/ol.425271] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 06/29/2021] [Indexed: 06/13/2023]
Abstract
Thinner than 10 nm layers of bismuth (Bi) were grown on (111) Si substrates by molecular beam epitaxy. Terahertz (THz) radiation pulses from these layers excited by tunable wavelength femtosecond optical pulses were measured. THz emission sets on when the photon energy exceeds 0.45 eV, which was explained by the semimetal-to-semiconductor transition at this Bi layer thickness. A THz signal has both isotropic and anisotropic components that could be caused by the lack of balance of lateral photocurrent components and the shift currents, respectively.
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22
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Park H, Jeong K, Maeng I, Sim KI, Pathak S, Kim J, Hong SB, Jung TS, Kang C, Kim JH, Hong J, Cho MH. Enhanced Spin-to-Charge Conversion Efficiency in Ultrathin Bi 2Se 3 Observed by Spintronic Terahertz Spectroscopy. ACS APPLIED MATERIALS & INTERFACES 2021; 13:23153-23160. [PMID: 33945256 DOI: 10.1021/acsami.1c03168] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Owing to their remarkable spin-charge conversion (SCC) efficiency, topological insulators (TIs) are the most attractive candidates for spin-orbit torque generators. The simple method of enhancing SCC efficiency is to reduce the thickness of TI films to minimize the trivial bulk contribution. However, when the thickness reaches the ultrathin regime, the SCC efficiency decreases owing to intersurface hybridization. To overcome these contrary effects, we induced dehybridization of the ultrathin TI film by breaking the inversion symmetry between surfaces. For the TI film grown on an oxygen-deficient transition-metal oxide, the unbonded transition-metal d-orbitals affected only the bottom surface, resulting in asymmetric surface band structures. Spintronic terahertz emission spectroscopy, an emerging tool for investigating the SCC characteristics, revealed that the resulting SCC efficiency in symmetry-broken ultrathin Bi2Se3 was enhanced by up to ∼2.4 times.
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Affiliation(s)
- Hanbum Park
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Kwangsik Jeong
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Division of Physics and Semiconductor Science, Dongguk University, Seoul 04620, Republic of Korea
| | - InHee Maeng
- YUHS-KRIBB, Medical Convergence Research Institute, College of Medicine, Yonsei University, Seoul 03722, Republic of Korea
| | - Kyung Ik Sim
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
| | - Sachin Pathak
- Department of Physics, School of Engineering, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand, India
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Jonghoon Kim
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Seok-Bo Hong
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Taek Sun Jung
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Chul Kang
- Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea
| | - Jae Hoon Kim
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Jongill Hong
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Mann-Ho Cho
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
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23
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Schmid CP, Weigl L, Grössing P, Junk V, Gorini C, Schlauderer S, Ito S, Meierhofer M, Hofmann N, Afanasiev D, Crewse J, Kokh KA, Tereshchenko OE, Güdde J, Evers F, Wilhelm J, Richter K, Höfer U, Huber R. Tunable non-integer high-harmonic generation in a topological insulator. Nature 2021; 593:385-390. [PMID: 34012087 DOI: 10.1038/s41586-021-03466-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 03/17/2021] [Indexed: 02/04/2023]
Abstract
When intense lightwaves accelerate electrons through a solid, the emerging high-order harmonic (HH) radiation offers key insights into the material1-11. Sub-optical-cycle dynamics-such as dynamical Bloch oscillations2-5, quasiparticle collisions6,12, valley pseudospin switching13 and heating of Dirac gases10-leave fingerprints in the HH spectra of conventional solids. Topologically non-trivial matter14,15 with invariants that are robust against imperfections has been predicted to support unconventional HH generation16-20. Here we experimentally demonstrate HH generation in a three-dimensional topological insulator-bismuth telluride. The frequency of the terahertz driving field sharply discriminates between HH generation from the bulk and from the topological surface, where the unique combination of long scattering times owing to spin-momentum locking17 and the quasi-relativistic dispersion enables unusually efficient HH generation. Intriguingly, all observed orders can be continuously shifted to arbitrary non-integer multiples of the driving frequency by varying the carrier-envelope phase of the driving field-in line with quantum theory. The anomalous Berry curvature warranted by the non-trivial topology enforces meandering ballistic trajectories of the Dirac fermions, causing a hallmark polarization pattern of the HH emission. Our study provides a platform to explore topology and relativistic quantum physics in strong-field control, and could lead to non-dissipative topological electronics at infrared frequencies.
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Affiliation(s)
- C P Schmid
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg, Germany
| | - L Weigl
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg, Germany
| | - P Grössing
- Institute of Theoretical Physics, University of Regensburg, Regensburg, Germany
| | - V Junk
- Institute of Theoretical Physics, University of Regensburg, Regensburg, Germany
| | - C Gorini
- Institute of Theoretical Physics, University of Regensburg, Regensburg, Germany.,Université Paris-Saclay, CEA, CNRS, SPEC, Gif-sur-Yvette, France
| | - S Schlauderer
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg, Germany
| | - S Ito
- Department of Physics, Philipps-University of Marburg, Marburg, Germany
| | - M Meierhofer
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg, Germany
| | - N Hofmann
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg, Germany
| | - D Afanasiev
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg, Germany
| | - J Crewse
- Institute of Theoretical Physics, University of Regensburg, Regensburg, Germany
| | - K A Kokh
- V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk, Russia.,Novosibirsk State University, Novosibirsk, Russia
| | - O E Tereshchenko
- Novosibirsk State University, Novosibirsk, Russia.,A.V. Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk, Russia
| | - J Güdde
- Department of Physics, Philipps-University of Marburg, Marburg, Germany
| | - F Evers
- Institute of Theoretical Physics, University of Regensburg, Regensburg, Germany
| | - J Wilhelm
- Institute of Theoretical Physics, University of Regensburg, Regensburg, Germany.
| | - K Richter
- Institute of Theoretical Physics, University of Regensburg, Regensburg, Germany.
| | - U Höfer
- Department of Physics, Philipps-University of Marburg, Marburg, Germany
| | - R Huber
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg, Germany.
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24
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Gueckstock O, Nádvorník L, Gradhand M, Seifert TS, Bierhance G, Rouzegar R, Wolf M, Vafaee M, Cramer J, Syskaki MA, Woltersdorf G, Mertig I, Jakob G, Kläui M, Kampfrath T. Terahertz Spin-to-Charge Conversion by Interfacial Skew Scattering in Metallic Bilayers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2006281. [PMID: 33506577 DOI: 10.1002/adma.202006281] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 12/24/2020] [Indexed: 06/12/2023]
Abstract
The efficient conversion of spin to charge transport and vice versa is of major relevance for the detection and generation of spin currents in spin-based electronics. Interfaces of heterostructures are known to have a marked impact on this process. Here, terahertz (THz) emission spectroscopy is used to study ultrafast spin-to-charge-current conversion (S2C) in about 50 prototypical F|N bilayers consisting of a ferromagnetic layer F (e.g., Ni81 Fe19 , Co, or Fe) and a nonmagnetic layer N with strong (Pt) or weak (Cu and Al) spin-orbit coupling. Varying the structure of the F/N interface leads to a drastic change in the amplitude and even inversion of the polarity of the THz charge current. Remarkably, when N is a material with small spin Hall angle, a dominant interface contribution to the ultrafast charge current is found. Its magnitude amounts to as much as about 20% of that found in the F|Pt reference sample. Symmetry arguments and first-principles calculations strongly suggest that the interfacial S2C arises from skew scattering of spin-polarized electrons at interface imperfections. The results highlight the potential of skew scattering for interfacial S2C and propose a promising route to enhanced S2C by tailored interfaces at all frequencies from DC to terahertz.
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Affiliation(s)
- Oliver Gueckstock
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany
| | - Lukáš Nádvorník
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany
- Faculty of Mathematics and Physics, Charles University, Ke Karlovu 2027/3, Prague, 12116, Czech Republic
| | - Martin Gradhand
- School of Physics, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, UK
- Institut für Physik, Johannes-Gutenberg-Universität Mainz, Staudingerweg 7, 55128, Mainz, Germany
| | - Tom Sebastian Seifert
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany
- Department of Materials, ETH Zürich, Hönggerbergring 64, Zürich, 8093, Switzerland
| | - Genaro Bierhance
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany
| | - Reza Rouzegar
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany
| | - Martin Wolf
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany
| | - Mehran Vafaee
- Institut für Physik, Johannes-Gutenberg-Universität Mainz, Staudingerweg 7, 55128, Mainz, Germany
| | - Joel Cramer
- Institut für Physik, Johannes-Gutenberg-Universität Mainz, Staudingerweg 7, 55128, Mainz, Germany
| | - Maria Andromachi Syskaki
- Institut für Physik, Johannes-Gutenberg-Universität Mainz, Staudingerweg 7, 55128, Mainz, Germany
- Singulus Technologies AG, 63796, Kahl am Main, Germany
| | - Georg Woltersdorf
- Institut für Physik, Martin-Luther-Universität Halle, Von-Danckelmann-Platz, 06120, Halle, Germany
| | - Ingrid Mertig
- Institut für Physik, Martin-Luther-Universität Halle, Von-Danckelmann-Platz, 06120, Halle, Germany
| | - Gerhard Jakob
- Institut für Physik, Johannes-Gutenberg-Universität Mainz, Staudingerweg 7, 55128, Mainz, Germany
| | - Mathias Kläui
- Institut für Physik, Johannes-Gutenberg-Universität Mainz, Staudingerweg 7, 55128, Mainz, Germany
| | - Tobias Kampfrath
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195, Berlin, Germany
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25
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Luo L, Cheng D, Song B, Wang LL, Vaswani C, Lozano PM, Gu G, Huang C, Kim RHJ, Liu Z, Park JM, Yao Y, Ho K, Perakis IE, Li Q, Wang J. A light-induced phononic symmetry switch and giant dissipationless topological photocurrent in ZrTe 5. NATURE MATERIALS 2021; 20:329-334. [PMID: 33462464 DOI: 10.1038/s41563-020-00882-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 11/17/2020] [Indexed: 06/12/2023]
Abstract
Dissipationless currents from topologically protected states are promising for disorder-tolerant electronics and quantum computation. Here, we photogenerate giant anisotropic terahertz nonlinear currents with vanishing scattering, driven by laser-induced coherent phonons of broken inversion symmetry in a centrosymmetric Dirac material ZrTe5. Our work suggests that this phononic terahertz symmetry switching leads to formation of Weyl points, whose chirality manifests in a transverse, helicity-dependent current, orthogonal to the dynamical inversion symmetry breaking axis, via circular photogalvanic effect. The temperature-dependent topological photocurrent exhibits several distinct features: Berry curvature dominance, particle-hole reversal near conical points and chirality protection that is responsible for an exceptional ballistic transport length of ~10 μm. These results, together with first-principles modelling, indicate two pairs of Weyl points dynamically created by B1u phonons of broken inversion symmetry. Such phononic terahertz control breaks ground for coherent manipulation of Weyl nodes and robust quantum transport without application of static electric or magnetic fields.
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Affiliation(s)
- Liang Luo
- Department of Physics and Astronomy, Iowa State University and Ames Laboratory, US Department of Energy, Ames, IA, USA
| | - Di Cheng
- Department of Physics and Astronomy, Iowa State University and Ames Laboratory, US Department of Energy, Ames, IA, USA
| | - Boqun Song
- Department of Physics and Astronomy, Iowa State University and Ames Laboratory, US Department of Energy, Ames, IA, USA
| | - Lin-Lin Wang
- Department of Physics and Astronomy, Iowa State University and Ames Laboratory, US Department of Energy, Ames, IA, USA
| | - Chirag Vaswani
- Department of Physics and Astronomy, Iowa State University and Ames Laboratory, US Department of Energy, Ames, IA, USA
| | - P M Lozano
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
| | - G Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA
| | - Chuankun Huang
- Department of Physics and Astronomy, Iowa State University and Ames Laboratory, US Department of Energy, Ames, IA, USA
| | - Richard H J Kim
- Department of Physics and Astronomy, Iowa State University and Ames Laboratory, US Department of Energy, Ames, IA, USA
| | - Zhaoyu Liu
- Department of Physics and Astronomy, Iowa State University and Ames Laboratory, US Department of Energy, Ames, IA, USA
| | - Joong-Mok Park
- Department of Physics and Astronomy, Iowa State University and Ames Laboratory, US Department of Energy, Ames, IA, USA
| | - Yongxin Yao
- Department of Physics and Astronomy, Iowa State University and Ames Laboratory, US Department of Energy, Ames, IA, USA
| | - Kaiming Ho
- Department of Physics and Astronomy, Iowa State University and Ames Laboratory, US Department of Energy, Ames, IA, USA
| | - Ilias E Perakis
- Department of Physics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Qiang Li
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA.
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA.
| | - Jigang Wang
- Department of Physics and Astronomy, Iowa State University and Ames Laboratory, US Department of Energy, Ames, IA, USA.
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26
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Xie F, Lian Z, Zhang S, Wang T, Miao S, Song Z, Ying Z, Pan XC, Long M, Zhang M, Fei F, Hu W, Yu G, Song F, Kang TT, Shi SF. Reversible engineering of topological insulator surface state conductivity through optical excitation. NANOTECHNOLOGY 2021; 32:17LT01. [PMID: 33620033 DOI: 10.1088/1361-6528/abde01] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Despite the broadband response, limited optical absorption at a particular wavelength hinders the development of optoelectronics based on Dirac fermions. Heterostructures of graphene and various semiconductors have been explored for this purpose, while non-ideal interfaces often limit the performance. The topological insulator (TI) is a natural hybrid system, with the surface states hosting high-mobility Dirac fermions and the small-bandgap semiconducting bulk state strongly absorbing light. In this work, we show a large photocurrent response from a field effect transistor device based on intrinsic TI Sn-Bi1.1Sb0.9Te2S (Sn-BSTS). The photocurrent response is non-volatile and sensitively depends on the initial Fermi energy of the surface state, and it can be erased by controlling the gate voltage. Our observations can be explained with a remote photo-doping mechanism, in which the light excites the defects in the bulk and frees the localized carriers to the surface state. This photodoping modulates the surface state conductivity without compromising the mobility, and it also significantly modify the quantum Hall effect of the surface state. Our work thus illustrates a route to reversibly manipulate the surface states through optical excitation, shedding light into utilizing topological surface states for quantum optoelectronics.
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Affiliation(s)
- Faji Xie
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, People's Republic of China
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27
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Tong M, Hu Y, Wang Z, Zhou T, Xie X, Cheng X, Jiang T. Enhanced Terahertz Radiation by Efficient Spin-to-Charge Conversion in Rashba-Mediated Dirac Surface States. NANO LETTERS 2021; 21:60-67. [PMID: 33331788 DOI: 10.1021/acs.nanolett.0c03079] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The enhancement of terahertz (THz) radiation is of extreme significance for the realization of the THz probe and imaging. However, present THz technologies are far from being enough to realize high-performance and room-temperature THz sources. Fortunately, topological insulators (TIs), with spin-momentum-locked Dirac surface states, are expected to exhibit a high terahertz emission efficiency. In this work, the novel concept of a Rashba-state-enhanced spintronic THz emitter is demonstrated on the basis of ferromagnet/heavy metal/topological insulator (FM/HM/TI) heterostructure. We find that the THz emission intensity changes as a function of HM interlayer thickness, and a 1.98 times higher intensity compared to that of FM/TI can be achieved when a meticulously designed thickness of the HM layer is inserted. The improvement of terahertz radiation is ascribed to the additive effect of Rashba splitting and topological surface states at the HM/TI interface. These results offer new possibilities for realizing spintronic THz emitters in TI-based magnetic heterostructures.
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Affiliation(s)
| | | | - Zhenyu Wang
- National Innovation Institute of Defense Technology, Academy of Military Sciences PLA China, Beijing 100010, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Tong Zhou
- National Innovation Institute of Defense Technology, Academy of Military Sciences PLA China, Beijing 100010, China
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28
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Giant topological longitudinal circular photo-galvanic effect in the chiral multifold semimetal CoSi. Nat Commun 2021; 12:154. [PMID: 33420054 PMCID: PMC7794406 DOI: 10.1038/s41467-020-20408-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Accepted: 12/02/2020] [Indexed: 11/08/2022] Open
Abstract
The absence of mirror symmetry, or chirality, is behind striking natural phenomena found in systems as diverse as DNA and crystalline solids. A remarkable example occurs when chiral semimetals with topologically protected band degeneracies are illuminated with circularly polarized light. Under the right conditions, the part of the generated photocurrent that switches sign upon reversal of the light's polarization, known as the circular photo-galvanic effect, is predicted to depend only on fundamental constants. The conditions to observe quantization are non-universal, and depend on material parameters and the incident frequency. In this work, we perform terahertz emission spectroscopy with tunable photon energy from 0.2 -1.1 eV in the chiral topological semimetal CoSi. We identify a large longitudinal photocurrent peaked at 0.4 eV reaching ~550 μ A/V2, which is much larger than the photocurrent in any chiral crystal reported in the literature. Using first-principles calculations we establish that the peak originates only from topological band crossings, reaching 3.3 ± 0.3 in units of the quantization constant. Our calculations indicate that the quantized circular photo-galvanic effect is within reach in CoSi upon doping and increase of the hot-carrier lifetime. The large photo-conductivity suggests that topological semimetals could potentially be used as novel mid-infrared detectors.
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29
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Hatada H, Nakamura M, Sotome M, Kaneko Y, Ogawa N, Morimoto T, Tokura Y, Kawasaki M. Defect tolerant zero-bias topological photocurrent in a ferroelectric semiconductor. Proc Natl Acad Sci U S A 2020; 117:20411-20415. [PMID: 32778597 PMCID: PMC7456187 DOI: 10.1073/pnas.2007002117] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Lattice defect is a major cause of energy dissipation in conventional electric current due to the drift and diffusion motions of electrons. Different nature of current emerges when noncentrosymmetric materials are excited by light. This current, called the shift current, originates from the change in the Berry connection of electrons' wave functions during the interband optical transition. Here, we demonstrate the defect tolerance of shift current using single crystals of ferroelectric semiconductor antimony sulfoiodide (SbSI). Although the dark conductance spreads over several orders of magnitude in each crystal due to the difference in the density of defect levels, the observed shift current converges to an identical value. We also reveal that the shift current is scarcely disturbed by the surface defects while they drastically suppress the conventional photocurrent. The defect tolerance is a manifestation of the topological nature of shift current, which will be a crucial advantage in optoelectronic applications.
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Affiliation(s)
- Hiroki Hatada
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Masao Nakamura
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan;
- PRESTO, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan
| | - Masato Sotome
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
| | - Yoshio Kaneko
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
| | - Naoki Ogawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
- PRESTO, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan
| | - Takahiro Morimoto
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
- PRESTO, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan
| | - Yoshinori Tokura
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
- Quantum-Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
- Tokyo College, University of Tokyo, Tokyo 113-8656, Japan
| | - Masashi Kawasaki
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
- Quantum-Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
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30
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Kaner N, Wei Y, Jiang Y, Li W, Xu X, Pang K, Li X, Yang J, Jiang Y, Zhang G, Tian WQ. Enhanced Shift Currents in Monolayer 2D GeS and SnS by Strain-Induced Band Gap Engineering. ACS OMEGA 2020; 5:17207-17214. [PMID: 32715206 PMCID: PMC7376894 DOI: 10.1021/acsomega.0c01319] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 06/22/2020] [Indexed: 06/11/2023]
Abstract
Group IV monochalcogenides exhibit spontaneous polarization and ferroelectricity, which are important in photovoltaic materials. Since strain engineering plays an important role in ferroelectricity, in the present work, the effect of equibiaxial strain on the band structure and shift currents in monolayer two-dimensional (2D) GeS and SnS has systematically been investigated using the first-principles calculations. The conduction bands of those materials are more responsive to strain than the valence bands. Increased equibiaxial compressive strain leads to a drastic reduction in the band gap and finally the occurrence of phase transition from semiconductor to metal at strains of -15 and -14% for GeS and SnS, respectively. On the other hand, tensile equibiaxial strain increases the band gap slightly. Similarly, increased equibiaxial compressive strain leads to a steady almost four times increase in the shift currents at a strain of -12% with direction change occurring at -8% strain. However, at phase transition from semiconductor to metal, the shift currents of the two materials completely vanish. Equibiaxial tensile strain also leads to increased shift currents. For SnS, shift currents do not change direction, just as the case of GeS at low strain; however, at a strain of +8% and beyond, direction reversal of shift currents beyond the band gap in GeS occur.
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Affiliation(s)
| | - Yadong Wei
- School
of Physics, Harbin Institute of Technology, Harbin 150001, China
| | - Yingjie Jiang
- School
of Physics, Harbin Institute of Technology, Harbin 150001, China
| | - Weiqi Li
- School
of Physics, Harbin Institute of Technology, Harbin 150001, China
| | - Xiaodong Xu
- School
of Physics, Harbin Institute of Technology, Harbin 150001, China
| | - Kaijuan Pang
- School
of Physics, Harbin Institute of Technology, Harbin 150001, China
| | - Xingji Li
- Materials
Science and Engineering, Harbin Institute
of Technology, Harbin 150001, China
| | - Jianqun Yang
- Materials
Science and Engineering, Harbin Institute
of Technology, Harbin 150001, China
| | - YongYuan Jiang
- School
of Physics, Harbin Institute of Technology, Harbin 150001, China
| | - Guiling Zhang
- School
of Materials Science and Engineering, Harbin
University of Science and Technology, Harbin 150080, China
| | - Wei Quan Tian
- Chongqing
Key Laboratory of Theoretical and Computational Chemistry, College
of Chemistry and Chemical Engineering, Chongqing
University, Huxi Campus, Chongqing 401331, China
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31
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Hong SB, Kim DK, Chae J, Kim K, Jeong K, Kim J, Park H, Yi Y, Cho MH. Enhanced Photoinduced Carrier Generation Efficiency through Surface Band Bending in Topological Insulator Bi 2Se 3 Thin Films by the Oxidized Layer. ACS APPLIED MATERIALS & INTERFACES 2020; 12:26649-26658. [PMID: 32397708 DOI: 10.1021/acsami.0c05165] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Topological insulators (TIs) have become popular in the field of optoelectronic devices because of their broadband and high-sensitivity properties, which are attributed to the narrow band gap of the bulk state and high mobility of the Dirac surface state. Although perfectly grown TIs are known to exhibit strong stability against oxidation, in most cases, the existence of vacancy defects in TIs reacts to air and the characteristics of TIs is affected by oxidation. Therefore, changes in the band structure and electrical characteristics by oxidation should be considered. A significant change occurs because of the oxidation; however, the dependence of the photoresponse of TIs on oxidation has not been studied in detail. In this study, the photoresponsivity of oxidized Bi2Se3 films is enhanced, rather than degraded, after oxidation in air for 24 h, resulting in a maximum responsivity of 140 mA W-1. This responsivity is substantially higher than previously reported values for Bi2Se3. Furthermore, a change in the photoresponse time of Bi2Se3 due to air exposure is systematically observed. Based on variations in the Fermi level and work function, using photoelectron spectroscopy, it is confirmed that the responsivity is improved from the junction effect of the Bi-based surface oxidized layer.
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Affiliation(s)
- Seok-Bo Hong
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Atomic-scale Surface Science Center, Yonsei University, Seoul 03722, Republic of Korea
| | - Dae-Kyoung Kim
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Atomic-scale Surface Science Center, Yonsei University, Seoul 03722, Republic of Korea
| | - Jimin Chae
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Atomic-scale Surface Science Center, Yonsei University, Seoul 03722, Republic of Korea
| | - Kiwoong Kim
- Institute of Physics and Applied Physics, Yonsei University, 50 Yonsei-ro, Seodaemun-go, Seoul 03722, Republic of Korea
| | - Kwangsik Jeong
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Atomic-scale Surface Science Center, Yonsei University, Seoul 03722, Republic of Korea
| | - Jonghoon Kim
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Atomic-scale Surface Science Center, Yonsei University, Seoul 03722, Republic of Korea
| | - Hanbum Park
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Atomic-scale Surface Science Center, Yonsei University, Seoul 03722, Republic of Korea
| | - Yeonjin Yi
- Institute of Physics and Applied Physics, Yonsei University, 50 Yonsei-ro, Seodaemun-go, Seoul 03722, Republic of Korea
| | - Mann-Ho Cho
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Atomic-scale Surface Science Center, Yonsei University, Seoul 03722, Republic of Korea
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32
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Gao Y, Kaushik S, Philip EJ, Li Z, Qin Y, Liu YP, Zhang WL, Su YL, Chen X, Weng H, Kharzeev DE, Liu MK, Qi J. Chiral terahertz wave emission from the Weyl semimetal TaAs. Nat Commun 2020; 11:720. [PMID: 32024831 PMCID: PMC7002692 DOI: 10.1038/s41467-020-14463-1] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 01/08/2020] [Indexed: 11/23/2022] Open
Abstract
Weyl semimetals host chiral fermions with distinct chiralities and spin textures. Optical excitations involving those chiral fermions can induce exotic carrier responses, and in turn lead to novel optical phenomena. Here, we discover strong coherent terahertz emission from Weyl semimetal TaAs, which is demonstrated as a unique broadband source of the chiral terahertz wave. The polarization control of the THz emission is achieved by tuning photoexcitation of ultrafast photocurrents via the photogalvanic effect. In the near-infrared regime, the photon-energy dependent nonthermal current due to the predominant circular photogalvanic effect can be attributed to the radical change of the band velocities when the chiral Weyl fermions are excited during selective optical transitions between the tilted anisotropic Weyl cones and the massive bulk bands. Our findings provide a design concept for creating chiral photon sources using quantum materials and open up new opportunities for developing ultrafast opto-electronics using Weyl physics.
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Affiliation(s)
- Y Gao
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - S Kaushik
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - E J Philip
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Z Li
- State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Beijing Key Laboratory of Quantum Devices, Peking University, Beijing, 100871, China
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Y Qin
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China
- Institute of Electronic and Information Engineering, University of Electronic Science and Technology of China, Dongguan, 523808, China
| | - Y P Liu
- Institute of Modern Physics, Fudan University, Shanghai, 200433, China
| | - W L Zhang
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Y L Su
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - X Chen
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - H Weng
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- Songshan Lake Materials Laboratory, Dongguan, 523808, China
| | - D E Kharzeev
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA.
- Department of Physics, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA.
- RIKEN-BNL Research Center, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA.
| | - M K Liu
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA.
| | - J Qi
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China.
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Cheng D, Liu Z, Luo L, Vaswani C, Park JM, Yao Y, Song Z, Huang C, Mudiyanselage DH, Kim RHJ, Yan Y, Ho KM, Wang J. Helicity-dependent terahertz photocurrent and phonon dynamics in hybrid metal halide perovskites. J Chem Phys 2019; 151:244706. [DOI: 10.1063/1.5127767] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- D. Cheng
- Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA
| | - Z. Liu
- Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA
| | - L. Luo
- Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA
| | - C. Vaswani
- Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA
| | - J.-M. Park
- Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA
| | - Y. Yao
- Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA
| | - Z. Song
- Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, University of Toledo, Toledo, Ohio 43606, USA
| | - C. Huang
- Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA
| | - D.-H. Mudiyanselage
- Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA
| | - R. H. J. Kim
- Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA
| | - Y. Yan
- Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, University of Toledo, Toledo, Ohio 43606, USA
| | - K.-M. Ho
- Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA
| | - J. Wang
- Department of Physics and Astronomy and Ames Laboratory-U.S. DOE, Iowa State University, Ames, Iowa 50011, USA
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34
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Wang YM, Yu JL, Zeng XL, Chen YH, Liu Y, Cheng SY, Lai YF, Yin CM, He K, Xue QK. Temperature and excitation wavelength dependence of circular and linear photogalvanic effect in a three dimensional topological insulator Bi 2Se 3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:415702. [PMID: 31220819 DOI: 10.1088/1361-648x/ab2b55] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The circular (CPGE) and linear photogalvanic effect (LPGE) of a three-dimensional topological insulator Bi2Se3 thin film of seven quintuple layers excited by near-infrared (1064 nm) and mid-infrared (10.6 [Formula: see text]m) radiations have been investigated. The comparison of the CPGE current measured parallel and perpendicular to the incident plane, together with the comparison of the CPGE current under front and back illuminations, indicates that the CPGE under front illumination of 1064 nm light is dominated by the top surface states of the Bi2Se3 thin film. The CPGE current excited by 10.6 [Formula: see text]m light is about one order larger than that excited by 1064 nm light, which may be attributed to the smaller cancelation effect of the CPGE generated in the two-dimensional electron gas when excited by 10.6 [Formula: see text]m light. Under the excitation of 1064 nm light, the LPGE current is dominated by the component which shows an even parity of incident angles, while the LPGE current excited by 10.6 [Formula: see text]m light is mainly contributed by the component which is an odd parity of incident angles. Both of the CPGE and LPGE currents excited by 1064 nm decrease with increasing temperature, which may be owing to the decrease of the momentum relaxation time and the stronger electron-electron scattering with increasing temperature, respectively.
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Affiliation(s)
- Y M Wang
- Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University, Fuzhou, People's Republic of China
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Soifer H, Gauthier A, Kemper AF, Rotundu CR, Yang SL, Xiong H, Lu D, Hashimoto M, Kirchmann PS, Sobota JA, Shen ZX. Band-Resolved Imaging of Photocurrent in a Topological Insulator. PHYSICAL REVIEW LETTERS 2019; 122:167401. [PMID: 31075004 DOI: 10.1103/physrevlett.122.167401] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 02/05/2019] [Indexed: 06/09/2023]
Abstract
We study the microscopic origins of photocurrent generation in the topological insulator Bi_{2}Se_{3} via time- and angle-resolved photoemission spectroscopy. We image the unoccupied band structure as it evolves following a circularly polarized optical excitation and observe an asymmetric electron population in momentum space, which is the spectroscopic signature of a photocurrent. By analyzing the rise times of the population we identify which occupied and unoccupied electronic states are coupled by the optical excitation. We conclude that photocurrents can only be excited via resonant optical transitions coupling to spin-orbital textured states. Our work provides a microscopic understanding of how to control photocurrents in systems with spin-orbit coupling and broken inversion symmetry.
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Affiliation(s)
- H Soifer
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - A Gauthier
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305, USA
| | - A F Kemper
- Department of Physics, North Carolina State University, Raleigh, North Carolina 27695, USA
| | - C R Rotundu
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - S-L Yang
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305, USA
| | - H Xiong
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305, USA
| | - D Lu
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - M Hashimoto
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - P S Kirchmann
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - J A Sobota
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305, USA
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Z-X Shen
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305, USA
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36
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Huang Y, Yao Z, He C, Zhu L, Zhang L, Bai J, Xu X. Terahertz surface and interface emission spectroscopy for advanced materials. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:153001. [PMID: 30669133 DOI: 10.1088/1361-648x/ab00c0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Surfaces and interfaces are of particular importance for optoelectronic and photonic materials as they are involved in many physical and chemical processes such as carrier dynamics, charge transfer, chemical bonding, transformation reactions and so on. Terahertz (THz) emission spectroscopy provides a sensitive and nondestructive method for surface or interface analysis of advanced materials ranging from graphene to transition metal dichalcogenides, topological insulators, hybrid perovskites, and mixed-dimensional heterostructures based on 2D materials. In this review paper, we start with the THz radiation mechanisms under ultrafast laser excitation. Then we concentrate on the recent progresses of THz emission spectroscopy on the surface and interface properties of advanced materials, including transient surface photocurrents, surface nonlinear polarization, surface states, interface potential, and gas molecule adsorption/desorption processes. This novel spectroscopic method can not only promote the development of new and compact THz sources, but also provide a nondestructive optical method for surface and interface characterization of photocurrent and nonlinear polarization dynamics of materials.
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Affiliation(s)
- Yuanyuan Huang
- Shaanxi Joint Lab of Graphene, State Key Lab Incubation Base of Photoelectric Technology and Functional Materials, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, Institute of Photonics and Photon-Technology, Northwest University, Xi'an 710069, People's Republic of China
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37
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Kushnir K, Qin Y, Shen Y, Li G, Fregoso BM, Tongay S, Titova LV. Ultrafast Zero-Bias Surface Photocurrent in Germanium Selenide: Promise for Terahertz Devices and Photovoltaics. ACS APPLIED MATERIALS & INTERFACES 2019; 11:5492-5498. [PMID: 30620173 DOI: 10.1021/acsami.8b17225] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Theory predicts that a large spontaneous electric polarization and concomitant inversion symmetry breaking in GeSe monolayers result in a strong shift current in response to their excitation in the visible range. Shift current is a coherent displacement of electron density on the order of a lattice constant upon above-bandgap photoexcitation. A second-order nonlinear effect, it is forbidden by the inversion symmetry in the bulk GeSe crystals. Here, we use terahertz (THz) emission spectroscopy to demonstrate that ultrafast photoexcitation with wavelengths straddling both edges of the visible spectrum, 400 and 800 nm, launches a shift current in the surface layer of a bulk GeSe crystal, where the inversion symmetry is broken. The direction of the surface shift current determined from the observed polarity of the emitted THz pulses depends only on the orientation of the sample and not on the linear polarization direction of the excitation. Strong absorption by the low-frequency infrared-active phonons in the bulk of GeSe limits the bandwidth and the amplitude of the emitted THz pulses. We predict that reducing GeSe thickness to a monolayer or a few layers will result in a highly efficient broadband THz emission. Experimental demonstration of THz emission by the surface shift current in bulk GeSe crystals puts this 2D material forward as a candidate for next-generation shift current photovoltaics, nonlinear photonic devices, and THz sources.
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Affiliation(s)
- Kateryna Kushnir
- Department of Physics , Worcester Polytechnic Institute , Worcester , Massachusetts 01609 , United States
| | - Ying Qin
- School for Engineering of Matter, Transport and Energy , Arizona State University , Tempe , Arizona 85287 , United States
| | - Yuxia Shen
- School for Engineering of Matter, Transport and Energy , Arizona State University , Tempe , Arizona 85287 , United States
| | - Guangjiang Li
- Department of Physics , Worcester Polytechnic Institute , Worcester , Massachusetts 01609 , United States
| | - Benjamin M Fregoso
- Department of Physics , Kent State University , Kent , Ohio 44242 , United States
| | - Sefaattin Tongay
- School for Engineering of Matter, Transport and Energy , Arizona State University , Tempe , Arizona 85287 , United States
| | - Lyubov V Titova
- Department of Physics , Worcester Polytechnic Institute , Worcester , Massachusetts 01609 , United States
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38
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Sotome M, Nakamura M, Fujioka J, Ogino M, Kaneko Y, Morimoto T, Zhang Y, Kawasaki M, Nagaosa N, Tokura Y, Ogawa N. Spectral dynamics of shift current in ferroelectric semiconductor SbSI. Proc Natl Acad Sci U S A 2019; 116:1929-1933. [PMID: 30670652 PMCID: PMC6369763 DOI: 10.1073/pnas.1802427116] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Photoexcitation in solids brings about transitions of electrons/holes between different electronic bands. If the solid lacks an inversion symmetry, these electronic transitions support spontaneous photocurrent due to the geometric phase of the constituting electronic bands: the Berry connection. This photocurrent, termed shift current, is expected to emerge on the timescale of primary photoexcitation process. We observe ultrafast evolution of the shift current in a prototypical ferroelectric semiconductor antimony sulfur iodide (SbSI) by detecting emitted terahertz electromagnetic waves. By sweeping the excitation photon energy across the bandgap, ultrafast electron dynamics as a source of terahertz emission abruptly changes its nature, reflecting a contribution of Berry connection on interband optical transition. The shift excitation carries a net charge flow and is followed by a swing over of the electron cloud on a subpicosecond timescale. Understanding these substantive characters of the shift current with the help of first-principles calculation will pave the way for its application to ultrafast sensors and solar cells.
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Affiliation(s)
- M Sotome
- RIKEN Center for Emergent Matter Science (CEMS), 351-0198 Wako, Japan;
| | - M Nakamura
- RIKEN Center for Emergent Matter Science (CEMS), 351-0198 Wako, Japan
- PRESTO, Japan Science and Technology Agency (JST), 332-0012 Kawaguchi, Japan
| | - J Fujioka
- PRESTO, Japan Science and Technology Agency (JST), 332-0012 Kawaguchi, Japan
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, 113-8656 Tokyo, Japan
| | - M Ogino
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, 113-8656 Tokyo, Japan
| | - Y Kaneko
- RIKEN Center for Emergent Matter Science (CEMS), 351-0198 Wako, Japan
| | - T Morimoto
- Department of Physics, University of California, Berkeley, CA 94720
| | - Y Zhang
- Solid State Chemistry, Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
- Institute for Theoretical Solid State Physics, Leibniz Institute for Solid State and Materials Research, 01069 Dresden, Germany
| | - M Kawasaki
- RIKEN Center for Emergent Matter Science (CEMS), 351-0198 Wako, Japan
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, 113-8656 Tokyo, Japan
| | - N Nagaosa
- RIKEN Center for Emergent Matter Science (CEMS), 351-0198 Wako, Japan
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, 113-8656 Tokyo, Japan
| | - Y Tokura
- RIKEN Center for Emergent Matter Science (CEMS), 351-0198 Wako, Japan
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, 113-8656 Tokyo, Japan
| | - N Ogawa
- RIKEN Center for Emergent Matter Science (CEMS), 351-0198 Wako, Japan
- PRESTO, Japan Science and Technology Agency (JST), 332-0012 Kawaguchi, Japan
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Mooshammer F, Sandner F, Huber MA, Zizlsperger M, Weigand H, Plankl M, Weyrich C, Lanius M, Kampmeier J, Mussler G, Grützmacher D, Boland JL, Cocker TL, Huber R. Nanoscale Near-Field Tomography of Surface States on (Bi 0.5Sb 0.5) 2Te 3. NANO LETTERS 2018; 18:7515-7523. [PMID: 30419748 DOI: 10.1021/acs.nanolett.8b03008] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Three-dimensional topological insulators (TIs) have attracted tremendous interest for their possibility to host massless Dirac Fermions in topologically protected surface states (TSSs), which may enable new kinds of high-speed electronics. However, recent reports have outlined the importance of band bending effects within these materials, which results in an additional two-dimensional electron gas (2DEG) with finite mass at the surface. TI surfaces are also known to be highly inhomogeneous on the nanoscale, which is masked in conventional far-field studies. Here, we use near-field microscopy in the mid-infrared spectral range to probe the local surface properties of custom-tailored (Bi0.5Sb0.5)2Te3 structures with nanometer precision in all three spatial dimensions. Applying nanotomography and nanospectroscopy, we reveal a few-nanometer-thick layer of high surface conductivity and retrieve its local dielectric function without assuming any model for the spectral response. This allows us to directly distinguish between different types of surface states. An intersubband transition within the massive 2DEG formed by quantum confinement in the bent conduction band manifests itself as a sharp, surface-bound, Lorentzian-shaped resonance. An additional broadband background in the imaginary part of the dielectric function may be caused by the TSS. Tracing the intersubband resonance with nanometer spatial precision, we observe changes of its frequency, likely originating from local variations of doping or/and the mixing ratio between Bi and Sb. Our results highlight the importance of studying the surfaces of these novel materials on the nanoscale to directly access the local optical and electronic properties via the dielectric function.
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Affiliation(s)
- Fabian Mooshammer
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Fabian Sandner
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Markus A Huber
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Martin Zizlsperger
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Helena Weigand
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Markus Plankl
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Christian Weyrich
- Peter Grünberg Institut 9 , Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance , 52425 Jülich , Germany
| | - Martin Lanius
- Peter Grünberg Institut 9 , Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance , 52425 Jülich , Germany
| | - Jörn Kampmeier
- Peter Grünberg Institut 9 , Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance , 52425 Jülich , Germany
| | - Gregor Mussler
- Peter Grünberg Institut 9 , Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance , 52425 Jülich , Germany
| | - Detlev Grützmacher
- Peter Grünberg Institut 9 , Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance , 52425 Jülich , Germany
| | - Jessica L Boland
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Tyler L Cocker
- Department of Physics and Astronomy , Michigan State University , East Lansing , Michigan 48824 , United States
| | - Rupert Huber
- Department of Physics , University of Regensburg , 93040 Regensburg , Germany
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40
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Huo N, Konstantatos G. Recent Progress and Future Prospects of 2D-Based Photodetectors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1801164. [PMID: 30066409 DOI: 10.1002/adma.201801164] [Citation(s) in RCA: 148] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 05/10/2018] [Indexed: 06/08/2023]
Abstract
Conventional semiconductors such as silicon- and indium gallium arsenide (InGaAs)-based photodetectors have encountered a bottleneck in modern electronics and photonics in terms of spectral coverage, low resolution, nontransparency, nonflexibility, and complementary metal-oxide-semiconductor (CMOS) incompatibility. New emerging two-dimensional (2D) materials such as graphene, transition metal dichalcogenides (TMDs), and their hybrid systems thereof, however, can circumvent all these issues benefitting from mechanically flexibility, extraordinary electronic and optical properties, as well as wafer-scale production and integration. Heterojunction-based photodiodes based on 2D materials offer ultrafast and broadband response from the visible to far-infrared range. Phototransistors based on 2D hybrid systems combined with other material platforms such as quantum dots, perovskites, organic materials, or plasmonic nanostructures yield ultrasensitive and broadband light-detection capabilities. Notably the facile integration of 2D photodetectors on silicon photonics or CMOS platforms paves the way toward high-performance, low-cost, broadband sensing and imaging modalities.
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Affiliation(s)
- Nengjie Huo
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, 08860, Barcelona, Spain
| | - Gerasimos Konstantatos
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, 08860, Barcelona, Spain
- ICREA-Institució Catalana de Recerca i Estudis Avançats, Lluis Companys 23, 08010, Barcelona, Spain
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41
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Wang X, Cheng L, Zhu D, Wu Y, Chen M, Wang Y, Zhao D, Boothroyd CB, Lam YM, Zhu JX, Battiato M, Song JCW, Yang H, Chia EEM. Ultrafast Spin-to-Charge Conversion at the Surface of Topological Insulator Thin Films. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1802356. [PMID: 30370615 DOI: 10.1002/adma.201802356] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 09/20/2018] [Indexed: 06/08/2023]
Abstract
Strong spin-orbit coupling, resulting in the formation of spin-momentum-locked surface states, endows topological insulators with superior spin-to-charge conversion characteristics, though the dynamics that govern it have remained elusive. Here, an all-optical method is presented, which enables unprecedented tracking of the ultrafast dynamics of spin-to-charge conversion in a prototypical topological insulator Bi2 Se3 /ferromagnetic Co heterostructure, down to the sub-picosecond timescale. Compared to pure Bi2 Se3 or Co, a giant terahertz emission is observed in the heterostructure that originates from spin-to-charge conversion, in which the topological surface states play a crucial role. A 0.12 ps timescale is identified that sets a technological speed limit of spin-to-charge conversion processes in topological insulators. In addition, it is shown that the spin-to-charge conversion efficiency is temperature independent in Bi2 Se3 as expected from the nature of the surface states, paving the way for designing next-generation high-speed optospintronic devices based on topological insulators at room temperature.
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Affiliation(s)
- Xinbo Wang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Liang Cheng
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
| | - Dapeng Zhu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Yang Wu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Mengji Chen
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Yi Wang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Daming Zhao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
| | - Chris B Boothroyd
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Yeng Ming Lam
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Jian-Xin Zhu
- Theoretical Division and Center for Integrated Nanotechnologies, Los Alamos National Laboratory, NM, 87545, USA
| | - Marco Battiato
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
- Institute of Solid State Physics, Vienna University of Technology, 1040, Vienna, Austria
| | - Justin C W Song
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
- Institute of High Performance Computing, Agency for Science, Technology, and Research, Singapore, 138632, Singapore
| | - Hyunsoo Yang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Elbert E M Chia
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
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42
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Huang SM, Lin LJ, Yan YJ, Yu SH, Chou MMC, Hsieh HF, Ho CJ, Chen RS. The Extremely Enhanced Photocurrent Response in Topological Insulator Nanosheets with High Conductance. NANOSCALE RESEARCH LETTERS 2018; 13:371. [PMID: 30465297 PMCID: PMC6249153 DOI: 10.1186/s11671-018-2758-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 10/15/2018] [Indexed: 06/09/2023]
Abstract
The photocurrent was performed in topological insulator nanosheets with different conductances. The higher photocurrent is observed in the nanosheet with higher conductance. The responsivity is proportional to the nanosheet conductance over two orders. The responsivity is independent of the light power intensity in vacuum, but responsivity drastically decreases at low power intensity in air. The ratio of the responsivity in air to that in vacuum is negatively proportional to the the inverse of the light power intensity. These behaviors are understood as the statistical photocurrent in a system with blocked molecules. The time constant decreases as the thickness increases. A longer time constant is observed in lower atmosphere pressure.
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Affiliation(s)
- Shiu-Ming Huang
- Department of Physics, National Sun Yat-Sen University, Kaohsiung, 80424 Taiwan
| | - Lin-Jie Lin
- Department of Physics, National Sun Yat-Sen University, Kaohsiung, 80424 Taiwan
| | - You-Jhih Yan
- Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung, 80424 Taiwan
| | - Shih-Hsun Yu
- Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung, 80424 Taiwan
| | - Mitch M. C. Chou
- Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung, 80424 Taiwan
- Center of Crystal Research, National Sun Yat-sen University, Kaohsiung, 80424 Taiwan
| | - Ho-Feng Hsieh
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei, 10607 Taiwan
| | - Chin-Jung Ho
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei, 10607 Taiwan
| | - Ruei-San Chen
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei, 10607 Taiwan
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43
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Reimann J, Schlauderer S, Schmid CP, Langer F, Baierl S, Kokh KA, Tereshchenko OE, Kimura A, Lange C, Güdde J, Höfer U, Huber R. Subcycle observation of lightwave-driven Dirac currents in a topological surface band. Nature 2018; 562:396-400. [DOI: 10.1038/s41586-018-0544-x] [Citation(s) in RCA: 107] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 07/26/2018] [Indexed: 11/09/2022]
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44
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Wang W, Wang X, Wang N, Ning X, Li H, Lu D, Liu X, Zhang Q, Huang Y. Bi 2Se 3 Sensitized TiO 2 Nanotube Films for Photogenerated Cathodic Protection of 304 Stainless Steel Under Visible Light. NANOSCALE RESEARCH LETTERS 2018; 13:295. [PMID: 30242603 PMCID: PMC6150863 DOI: 10.1186/s11671-018-2717-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Accepted: 09/13/2018] [Indexed: 06/08/2023]
Abstract
Titanium dioxide (TiO2) nanotube arrays coupled with a narrow gap semiconductor-bismuth selenide (Bi2Se3)-exhibited remarkable enhancement in the photocathodic protection property for 304 stainless steel under visible light. Bi2Se3/TiO2 nanocomposites were successfully synthesized using a simple two-step method, including an electrochemical anodization method for preparing pure TiO2 and a chemical bath deposition method for synthesizing Bi2Se3 nanoflowers. The morphology and structure of the composite films were studied by scanning electron microscopy, energy dispersion spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. In addition, the influence of the Bi2Se3 content on the photoelectrochemical and photocathodic protection properties of the composite films was also studied. The photocurrent density of the Bi2Se3/TiO2 nanocomposites was significantly higher than that of pure TiO2 under visible light. The sensitizer Bi2Se3 enhanced the efficient separation of the photogenerated electron-hole pairs and the photocathodic protection properties of TiO2. Under visible light illumination, Bi2Se3/TiO2 nanocomposites synthesized by the chemical bath deposition method with Bi3+ (0.5 mmol/L) exhibited the optimal photogenerated cathodic protection performance for 304 stainless steel.
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Affiliation(s)
- Wencheng Wang
- Key Laboratory of Marine Environmental Corrosion and Bio-fouling, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao, 266071 China
- Open Studio for Marine Corrosion and Protection, Pilot National Laboratory for Marine Science and Technology, Qingdao, 266237 China
- University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Xiutong Wang
- Key Laboratory of Marine Environmental Corrosion and Bio-fouling, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao, 266071 China
- Open Studio for Marine Corrosion and Protection, Pilot National Laboratory for Marine Science and Technology, Qingdao, 266237 China
- Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, 266071 China
| | - Ning Wang
- Key Laboratory of Marine Environmental Corrosion and Bio-fouling, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao, 266071 China
- University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Xiaobo Ning
- Open Studio for Marine Corrosion and Protection, Pilot National Laboratory for Marine Science and Technology, Qingdao, 266237 China
| | - Hong Li
- College of Mechanical and Electrical Engineering, Qingdao University, Qingdao, 266071 China
| | - Dongzhu Lu
- Key Laboratory of Marine Environmental Corrosion and Bio-fouling, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao, 266071 China
| | - Xiangju Liu
- Key Laboratory of Marine Environmental Corrosion and Bio-fouling, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao, 266071 China
- University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Qichao Zhang
- Key Laboratory of Marine Environmental Corrosion and Bio-fouling, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao, 266071 China
- University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Yanliang Huang
- Key Laboratory of Marine Environmental Corrosion and Bio-fouling, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao, 266071 China
- Open Studio for Marine Corrosion and Protection, Pilot National Laboratory for Marine Science and Technology, Qingdao, 266237 China
- Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, 266071 China
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45
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Jnawali G, Linser S, Shojaei IA, Pournia S, Jackson HE, Smith LM, Need RF, Wilson SD. Revealing Optical Transitions and Carrier Recombination Dynamics within the Bulk Band Structure of Bi 2Se 3. NANO LETTERS 2018; 18:5875-5884. [PMID: 30106301 DOI: 10.1021/acs.nanolett.8b02577] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Bismuth selenide (Bi2Se3) is a prototypical 3D topological insulator whose Dirac surface states have been extensively studied theoretically and experimentally. Surprisingly little, however, is known about the energetics and dynamics of electrons and holes within the bulk band structure of the semiconductor. We use mid-infrared femtosecond transient reflectance measurements on a single nanoflake to study the ultrafast thermalization and recombination dynamics of photoexcited electrons and holes within the extended bulk band structure over a wide energy range (0.3 to 1.2 eV). Theoretical modeling of the reflectivity spectral line shapes at 10 K demonstrates that the electrons and holes are photoexcited within a dense and cold electron gas with a Fermi level positioned well above the bottom of the lowest conduction band. Direct optical transitions from the first and the second spin-orbit split valence bands to the Fermi level above the lowest conduction band minimum are identified. The photoexcited carriers thermalize rapidly to the lattice temperature within a couple of picoseconds due to optical phonon emission and scattering with the cold electron gas. The minority carrier holes recombine with the dense electron gas within 150 ps at 10 K and 50 ps at 300 K. Such knowledge of interaction of electrons and holes within the bulk band structure provides a foundation for understanding how such states interact dynamically with the topologically protected Dirac surface states.
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Affiliation(s)
- Giriraj Jnawali
- Department of Physics , University of Cincinnati , Cincinnati , Ohio 45221 , United States
| | - Samuel Linser
- Department of Physics , University of Cincinnati , Cincinnati , Ohio 45221 , United States
| | - Iraj Abbasian Shojaei
- Department of Physics , University of Cincinnati , Cincinnati , Ohio 45221 , United States
| | - Seyyedesadaf Pournia
- Department of Physics , University of Cincinnati , Cincinnati , Ohio 45221 , United States
| | - Howard E Jackson
- Department of Physics , University of Cincinnati , Cincinnati , Ohio 45221 , United States
| | - Leigh M Smith
- Department of Physics , University of Cincinnati , Cincinnati , Ohio 45221 , United States
| | - Ryan F Need
- Materials Department , University of California , Santa Barbara , California 93106 , United States
| | - Stephen D Wilson
- Materials Department , University of California , Santa Barbara , California 93106 , United States
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46
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Seifert TS, Jaiswal S, Barker J, Weber ST, Razdolski I, Cramer J, Gueckstock O, Maehrlein SF, Nadvornik L, Watanabe S, Ciccarelli C, Melnikov A, Jakob G, Münzenberg M, Goennenwein STB, Woltersdorf G, Rethfeld B, Brouwer PW, Wolf M, Kläui M, Kampfrath T. Femtosecond formation dynamics of the spin Seebeck effect revealed by terahertz spectroscopy. Nat Commun 2018; 9:2899. [PMID: 30042421 PMCID: PMC6057952 DOI: 10.1038/s41467-018-05135-2] [Citation(s) in RCA: 92] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2017] [Accepted: 06/13/2018] [Indexed: 11/09/2022] Open
Abstract
Understanding the transfer of spin angular momentum is essential in modern magnetism research. A model case is the generation of magnons in magnetic insulators by heating an adjacent metal film. Here, we reveal the initial steps of this spin Seebeck effect with <27 fs time resolution using terahertz spectroscopy on bilayers of ferrimagnetic yttrium iron garnet and platinum. Upon exciting the metal with an infrared laser pulse, a spin Seebeck current js arises on the same ~100 fs time scale on which the metal electrons thermalize. This observation highlights that efficient spin transfer critically relies on carrier multiplication and is driven by conduction electrons scattering off the metal–insulator interface. Analytical modeling shows that the electrons’ dynamics are almost instantaneously imprinted onto js because their spins have a correlation time of only ~4 fs and deflect the ferrimagnetic moments without inertia. Applications in material characterization, interface probing, spin-noise spectroscopy and terahertz spin pumping emerge. Probing spin pumping in the terahertz regime allows one to reveal its initial elementary steps. Here, the authors show that the formation of the spin Seebeck current in YIG/Pt critically relies on hot thermalized metal electrons because they impinge on the metal-insulator interface with maximum noise.
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Affiliation(s)
- Tom S Seifert
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany.,Department of Physics, Freie Universität Berlin, 14195, Berlin, Germany
| | - Samridh Jaiswal
- Institute of Physics, Johannes Gutenberg University Mainz, 55099, Mainz, Germany.,Singulus Technologies AG, 63796, Kahl am Main, Germany
| | - Joseph Barker
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - Sebastian T Weber
- Department of Physics and Research Center OPTIMAS, Technische Universität Kaiserslautern, 67663, Kaiserslautern, Germany
| | - Ilya Razdolski
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany
| | - Joel Cramer
- Institute of Physics, Johannes Gutenberg University Mainz, 55099, Mainz, Germany
| | - Oliver Gueckstock
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany
| | - Sebastian F Maehrlein
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany
| | - Lukas Nadvornik
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany.,Department of Physics, Freie Universität Berlin, 14195, Berlin, Germany
| | - Shun Watanabe
- Department of Advanced Materials Science, School of Frontier Sciences, University of Tokyo, Chiba, 277-8561, Japan
| | - Chiara Ciccarelli
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Alexey Melnikov
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany.,Institute of Physics, Martin-Luther-Universität Halle, 06120, Halle, Germany
| | - Gerhard Jakob
- Institute of Physics, Johannes Gutenberg University Mainz, 55099, Mainz, Germany
| | - Markus Münzenberg
- Institut für Physik, Universität Greifswald, 17489, Greifswald, Germany
| | - Sebastian T B Goennenwein
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062, Dresden, Germany
| | - Georg Woltersdorf
- Institute of Physics, Martin-Luther-Universität Halle, 06120, Halle, Germany
| | - Baerbel Rethfeld
- Department of Physics and Research Center OPTIMAS, Technische Universität Kaiserslautern, 67663, Kaiserslautern, Germany
| | - Piet W Brouwer
- Department of Physics, Freie Universität Berlin, 14195, Berlin, Germany
| | - Martin Wolf
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany
| | - Mathias Kläui
- Institute of Physics, Johannes Gutenberg University Mainz, 55099, Mainz, Germany
| | - Tobias Kampfrath
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany. .,Department of Physics, Freie Universität Berlin, 14195, Berlin, Germany.
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47
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A cascading nonlinear magneto-optical effect in topological insulators. Sci Rep 2018; 8:3908. [PMID: 29500471 PMCID: PMC5834634 DOI: 10.1038/s41598-018-22196-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 02/19/2018] [Indexed: 11/12/2022] Open
Abstract
Topological insulators (TIs) are characterized by possessing metallic (gapless) surface states and a finite band-gap state in the bulk. As the thickness of a TI layer decreases down to a few nanometers, hybridization between the top and bottom surfaces takes place due to quantum tunneling, consequently at a critical thickness a crossover from a 3D-TI to a 2D insulator occurs. Although such a crossover is generally accessible by scanning tunneling microscopy, or by angle-resolved photoemission spectroscopy, such measurements require clean surfaces. Here, we demonstrate that a cascading nonlinear magneto-optical effect induced via strong spin-orbit coupling can examine such crossovers. The helicity dependence of the time-resolved Kerr rotation exhibits a robust change in periodicity at a critical thickness, from which it is possible to predict the formation of a Dirac cone in a film several quintuple layers thick. This method enables prediction of a Dirac cone using a fundamental nonlinear optical effect that can be applied to a wide range of TIs and related 2D materials.
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48
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Yu J, Zeng X, Zhang L, Yin C, Chen Y, Liu Y, Cheng S, Lai Y, He K, Xue Q. Inverse spin Hall effect induced by linearly polarized light in the topological insulator Bi 2Se 3. OPTICS EXPRESS 2018; 26:4832-4841. [PMID: 29475328 DOI: 10.1364/oe.26.004832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 02/06/2018] [Indexed: 06/08/2023]
Abstract
The inverse spin Hall effect (ISHE) induced by the normal incidence of linearly-polarized infrared radiation has been observed in the topological insulator Bi2Se3. A model has been proposed to explain the phenomenon, and the spin transverse force has been determined by the model fitting. The anomalous linear photogalvanic effect (ALPGE) is also observed, and the photoinduced momentum anisotropy is extracted. Furthermore, the ISHE and ALPGE are investigated at different temperatures between 77 and 300 K, and the temperature dependence of the spin transverse force and photoinduced momentum anisotropy are obtained. This study suggests a new way to investigate the inverse spin Hall effect via linearly polarized light even at room temperature.
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49
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Zeng M, Xiao Y, Liu J, Yang K, Fu L. Exploring Two-Dimensional Materials toward the Next-Generation Circuits: From Monomer Design to Assembly Control. Chem Rev 2018; 118:6236-6296. [DOI: 10.1021/acs.chemrev.7b00633] [Citation(s) in RCA: 298] [Impact Index Per Article: 49.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Mengqi Zeng
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China
| | - Yao Xiao
- The Institute for Advanced Studies (IAS), Wuhan University, Wuhan 430072, China
| | - Jinxin Liu
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China
| | - Kena Yang
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China
| | - Lei Fu
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China
- The Institute for Advanced Studies (IAS), Wuhan University, Wuhan 430072, China
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50
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Seifert P, Vaklinova K, Ganichev S, Kern K, Burghard M, Holleitner AW. Spin Hall photoconductance in a three-dimensional topological insulator at room temperature. Nat Commun 2018; 9:331. [PMID: 29362413 PMCID: PMC5780383 DOI: 10.1038/s41467-017-02671-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 12/18/2017] [Indexed: 11/29/2022] Open
Abstract
Three-dimensional topological insulators are a class of Dirac materials, wherein strong spin-orbit coupling leads to two-dimensional surface states. The latter feature spin-momentum locking, i.e., each momentum vector is associated with a spin locked perpendicularly to it in the surface plane. While the principal spin generation capability of topological insulators is well established, comparatively little is known about the interaction of the spins with external stimuli like polarized light. We observe a helical, bias-dependent photoconductance at the lateral edges of topological Bi2Te2Se platelets for perpendicular incidence of light. The same edges exhibit also a finite bias-dependent Kerr angle, indicative of spin accumulation induced by a transversal spin Hall effect in the bulk states of the Bi2Te2Se platelets. A symmetry analysis shows that the helical photoconductance is distinct to common longitudinal photoconductance and photocurrent phenomena, but consistent with optically injected spins being transported in the side facets of the platelets. While the spin generation in topological insulators is well studied, little is known about the interaction of the spins with external stimuli. Here, Seifert et al. observe a helical, bias-dependent photoconductance at the lateral edges of topological Bi2Te2Se platelets for perpendicular incidence of light, distinct to common longitudinal photoconductance phenomena.
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Affiliation(s)
- Paul Seifert
- Walter Schottky Institut and Physik-Department, Technische Universität München, Am Coulombwall 4a, D-85748, Garching, Germany
| | - Kristina Vaklinova
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569, Stuttgart, Germany
| | - Sergey Ganichev
- Terahertz Center, University of Regensburg, D-93040, Regensburg, Germany
| | - Klaus Kern
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569, Stuttgart, Germany.,Institut de Physique, Ecole Polytechnique Fédérale de Lausanne, CH-1015, Lausanne, Switzerland
| | - Marko Burghard
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569, Stuttgart, Germany
| | - Alexander W Holleitner
- Walter Schottky Institut and Physik-Department, Technische Universität München, Am Coulombwall 4a, D-85748, Garching, Germany.
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