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Boland JL, Damry DA, Xia CQ, Schönherr P, Prabhakaran D, Herz LM, Hesjedal T, Johnston MB. Narrowband, Angle-Tunable, Helicity-Dependent Terahertz Emission from Nanowires of the Topological Dirac Semimetal Cd 3As 2. ACS PHOTONICS 2023; 10:1473-1484. [PMID: 37215322 PMCID: PMC10197169 DOI: 10.1021/acsphotonics.3c00068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Indexed: 05/24/2023]
Abstract
All-optical control of terahertz pulses is essential for the development of optoelectronic devices for next-generation quantum technologies. Despite substantial research in THz generation methods, polarization control remains difficult. Here, we demonstrate that by exploiting band structure topology, both helicity-dependent and helicity-independent THz emission can be generated from nanowires of the topological Dirac semimetal Cd3As2. We show that narrowband THz pulses can be generated at oblique incidence by driving the system with optical (1.55 eV) pulses with circular polarization. Varying the incident angle also provides control of the peak emission frequency, with peak frequencies spanning 0.21-1.40 THz as the angle is tuned from 15 to 45°. We therefore present Cd3As2 nanowires as a promising novel material platform for controllable terahertz emission.
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Affiliation(s)
- Jessica L. Boland
- Photon
Science Institute, Department of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL, U.K.
| | - Djamshid A. Damry
- Photon
Science Institute, Department of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL, U.K.
| | - Chelsea Q. Xia
- Department
of Physics, University of Oxford, Clarendon
Laboratory, Parks Road, Oxford OX1
3PU, U.K.
| | - Piet Schönherr
- Department
of Physics, University of Oxford, Clarendon
Laboratory, Parks Road, Oxford OX1
3PU, U.K.
| | - Dharmalingam Prabhakaran
- Department
of Physics, University of Oxford, Clarendon
Laboratory, Parks Road, Oxford OX1
3PU, U.K.
| | - Laura M. Herz
- Department
of Physics, University of Oxford, Clarendon
Laboratory, Parks Road, Oxford OX1
3PU, U.K.
| | - Thorsten Hesjedal
- Department
of Physics, University of Oxford, Clarendon
Laboratory, Parks Road, Oxford OX1
3PU, U.K.
| | - Michael B. Johnston
- Department
of Physics, University of Oxford, Clarendon
Laboratory, Parks Road, Oxford OX1
3PU, U.K.
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2
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Vaughan M, Michailow W, Salih M, Li L, Beere H, Ritchie DA, Linfield EH, Davies AG, Cunningham JE. Directed delivery of terahertz frequency radiation from quantum cascade lasers within a dry 3He dilution refrigerator. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:113906. [PMID: 36461439 DOI: 10.1063/5.0102553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Accepted: 10/08/2022] [Indexed: 06/17/2023]
Abstract
We present a scheme for the full integration of terahertz (THz) frequency quantum cascade lasers (QCLs) within a dilution refrigerator in order to provide a directed delivery of THz power into the sample space. We describe a successful operation of a 2.68 THz QCL located on the pulse tube cooler stage of the refrigerator, with its output coupled onto a two-dimensional electron gas (2DEG) located on a milli-kelvin sample stage via hollow metal waveguides and Hysol thermal isolators, achieving a total loss from QCL to the sample of ∼-9 dB. The thermal isolators limit heat leaks to the sample space, with a base temperature of ∼210 mK being achieved. We observe cyclotron resonance (CR) induced in the 2DEG by the QCL and explore the heating impact of the QCL on all stages of the refrigerator. The CR effect induced by the THz QCL is observable at electron temperatures as low as ∼430 mK. The results show a viable route for the exploitation of THz QCLs within the environment of a dilution refrigerator and for the THz power delivery in very low-temperature (<0.5 K) condensed matter experiments.
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Affiliation(s)
- M Vaughan
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, West Yorkshire LS2 9JT, United Kingdom
| | - W Michailow
- Cavendish Laboratory, University of Cambridge, Cambridge, Cambridgeshire CB3 0HE, United Kingdom
| | - M Salih
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, West Yorkshire LS2 9JT, United Kingdom
| | - L Li
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, West Yorkshire LS2 9JT, United Kingdom
| | - H Beere
- Cavendish Laboratory, University of Cambridge, Cambridge, Cambridgeshire CB3 0HE, United Kingdom
| | - D A Ritchie
- Cavendish Laboratory, University of Cambridge, Cambridge, Cambridgeshire CB3 0HE, United Kingdom
| | - E H Linfield
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, West Yorkshire LS2 9JT, United Kingdom
| | - A G Davies
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, West Yorkshire LS2 9JT, United Kingdom
| | - J E Cunningham
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, West Yorkshire LS2 9JT, United Kingdom
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3
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Synthesis and characterization of a Sb 2Te 3/Bi 2Te 3 p-n junction heterostructure via electrodeposition in nanoporous membranes. iScience 2021; 24:102694. [PMID: 34195570 PMCID: PMC8233195 DOI: 10.1016/j.isci.2021.102694] [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: 02/01/2021] [Revised: 05/24/2021] [Accepted: 06/03/2021] [Indexed: 11/22/2022] Open
Abstract
Topological insulators (TIs) are bulk insulators with metallic surface states that can be described by a single Dirac cone. However, low-dimensional solids such as nanowires (NWs) are a challenge, due to the difficulty of separating surface contributions from bulk carriers. Fabrication of NWs with high surface-to-volume ratio can be realized by different methods such as chemical vapor transport, molecular beam epitaxy, and electrodeposition. The last method is used in the present work allowing the growth of structures such as p-n junctions, intercalation of magnetic or superconducting dots. We report the synthesis of high-quality TI NW: Bi2Te3, Sb2Te3 and p-n junction via electrodeposition. Structural, morphological, and nanostructure properties of NWs have been investigated by various characterization techniques. Interface structures and lateral heterojunctions (LHJ) in p-n junction NWs has also been made.
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4
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KOBAYASHI T. Advanced time-resolved absorption spectroscopy with an ultrashort visible/near IR laser and a multi-channel lock-in detector. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2021; 97:236-260. [PMID: 33980754 PMCID: PMC8141836 DOI: 10.2183/pjab.97.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 02/17/2021] [Indexed: 06/12/2023]
Abstract
Ultrashort visible-near infrared (NIR) pulse generation and its applications to ultrafast spectroscopy are discussed. Femtosecond pulses of around 800 nm from a Ti:sapphire laser are used as a pump of an optical parametric amplifier (OPA) in a non-collinear configuration to generate ultrashort visible (500-780 nm) pulses and deep-ultraviolet (DUV, 259-282 nm) pulses. The visible-NIR pulses and DUV pulses were compressed to 3.9 fs and 10.4 fs, respectively, and used to elucidate various ultrafast dynamics in condensed matter with a sub-10 fs resolution by pump-probe measurements. We have also developed a 128-channel lock-in amplifier. The combined system of the world-shortest visible pulse from the OPA and the lock-in amplifier with the world-largest channel-number can clarify the sub-10 fs-dynamics in condensed matter. This system clarified structural changes in an excited state, reaction intermediate, and a transition state. This is possible even during molecular vibration and reactions via a real-time-resolved vibronic spectrum, which provides molecular structural change information. Also, ultrafast dynamics in exotic materials like carbon nanotubes, topological insulators, and novel solar battery systems have been clarified. Furthermore, the carrier-envelope phase in the ultrashort pulse has been controlled and measured.
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Affiliation(s)
- Takayoshi KOBAYASHI
- Center for Neuroscience and Biomedical Engineering, The University of Electro-Communications, Chofu, Tokyo, Japan
- Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
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5
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Yeh TT, Tu CM, Lin WH, Cheng CM, Tzeng WY, Chang CY, Shirai H, Fuji T, Sankar R, Chou FC, Gospodinov MM, Kobayashi T, Luo CW. Femtosecond time-evolution of mid-infrared spectral line shapes of Dirac fermions in topological insulators. Sci Rep 2020; 10:9803. [PMID: 32555237 PMCID: PMC7299937 DOI: 10.1038/s41598-020-66720-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 05/19/2020] [Indexed: 11/09/2022] Open
Abstract
Mid-infrared (MIR) light sources have much potential in the study of Dirac-fermions (DFs) in graphene and topological insulators (TIs) because they have a low photon energy. However, the topological surface state transitions (SSTs) in Dirac cones are veiled by the free carrier absorption (FCA) with same spectral line shape that is always seen in static MIR spectra. Therefore, it is difficult to distinguish the SST from the FCA, especially in TIs. Here, we disclose the abnormal MIR spectrum feature of transient reflectivity changes (ΔR/R) for the non-equilibrium states in TIs, and further distinguish FCA and spin-momentum locked SST using time-resolved and linearly polarized ultra-broadband MIR spectroscopy with no environmental perturbation. Although both effects produce similar features in the reflection spectra, they produce completely different variations in the ΔR/R to show their intrinsic ultrafast dynamics.
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Affiliation(s)
- Tien-Tien Yeh
- Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan.
- National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan.
| | - Chien-Ming Tu
- Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
| | - Wen-Hao Lin
- Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
| | - Cheng-Maw Cheng
- National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan
| | - Wen-Yen Tzeng
- Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
| | - Chen-Yu Chang
- Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
| | - Hideto Shirai
- Institute for Molecular Science, 38 Nishigonaka, Myodaiji, Okazaki, 444-8585, Japan
| | - Takao Fuji
- Institute for Molecular Science, 38 Nishigonaka, Myodaiji, Okazaki, 444-8585, Japan
- Toyota Technological Institute, 2-12-1 Hisakata, Tempaku-ku, Nagoya, 468-8511, Japan
| | - Raman Sankar
- Institute of Physics, Academia Sinica, Nankang, Taipei, R.O.C, 11529, Taiwan
- Center for Condensed Matter Sciences, National Taiwan University, Taipei, 10617, Taiwan
| | - Fang-Cheng Chou
- National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan
- Center for Condensed Matter Sciences, National Taiwan University, Taipei, 10617, Taiwan
| | - Marin M Gospodinov
- Institute of Solid State Physics, Bulgarian Academy of Sciences, 1784, Sofia, EU, Bulgaria
| | - Takayoshi Kobayashi
- Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
- Brain science Inspired Life Support Research Center, The University of Electro-Communications, 1-5 1 Chofugaoka, Chofu, Tokyo, 182-8585, Japan
| | - Chih-Wei Luo
- Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan.
- Taiwan Consortium of Emergent Crystalline Materials (TCECM), Ministry of Science and Technology, Taipei, Taiwan.
- Center for Emergent Functional Matter Science, National Chiao Tung University, Hsinchu, 30010, Taiwan.
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6
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Yu J, Xia L, Zhu K, Pan Q, Zeng X, Chen Y, Liu Y, Yin C, Cheng S, Lai Y, He K, Xue Q. Control of Circular Photogalvanic Effect of Surface States in the Topological Insulator Bi 2Te 3 via Spin Injection. ACS APPLIED MATERIALS & INTERFACES 2020; 12:18091-18100. [PMID: 32212669 DOI: 10.1021/acsami.9b23389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The circular photogalvanic effect (CPGE) provides a method utilizing circularly polarized light to control spin photocurrent and will also lead to novel opto-spintronic devices. The CPGE of three-dimensional topological insulator Bi2Te3 with different substrates and thicknesses has been systematically investigated. It is found that the CPGE current can be dramatically tuned by adopting different substrates. The CPGE current of the Bi2Te3 films on Si substrates are more than two orders larger than that on SrTiO3 substrates when illuminated by 1064 nm light, which can be attributed to the modulation effect due to the spin injection from Si substrate to Bi2Te3 films, larger light absorption coefficient, and stronger inequivalence between the top and bottom surface states for Bi2Te3 films grown on Si substrates. The excitation power dependence of the CPGE current of Bi2Te3 films on Si substrates shows a saturation at high power especially for thicker samples, whereas that on SrTiO3 substrates almost linearly increases with excitation power. Temperature dependence of the CPGE current of Bi2Te3 films on Si substrates first increases and then decreases with decreasing temperature, whereas that on SrTiO3 substrates changes monotonously with temperature. These interesting phenomena of the CPGE current of Bi2Te3 films on Si substrates are related to the spin injection from Si substrates to Bi2Te3 films. Our work not only intrigues new physics but also provides a method to effectively manipulate the helicity-dependent photocurrent via spin injection.
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Affiliation(s)
- Jinling Yu
- Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University, Fuzhou 350108, China
| | - Lijia Xia
- Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University, Fuzhou 350108, China
| | - Kejing Zhu
- Department of Physics, State Key Laboratory of Low Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
| | - Qinggao Pan
- Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University, Fuzhou 350108, China
| | - Xiaolin Zeng
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
- College of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yonghai Chen
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
- College of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yu Liu
- Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
- College of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chunming Yin
- School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia
- CAS Key Laboratory of Microscale Magnetic Resonance, Department of Modern Physics, Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Shuying Cheng
- Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University, Fuzhou 350108, China
- Jiangsu Collaborative Innovation Center of Photovolatic Science and Engineering, Changzhou University, Changzhou 213164, Jiangsu ,China
| | - Yunfeng Lai
- Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University, Fuzhou 350108, China
| | - Ke He
- Department of Physics, State Key Laboratory of Low Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
| | - Qikun Xue
- Department of Physics, State Key Laboratory of Low Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
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7
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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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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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9
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Possible flat band bending of the Bi 1.5Sb 0.5Te 1.7Se 1.3 crystal cleaved in an ambient air probed by terahertz emission spectroscopy. Sci Rep 2016; 6:36343. [PMID: 27805036 PMCID: PMC5090861 DOI: 10.1038/srep36343] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 10/14/2016] [Indexed: 01/08/2023] Open
Abstract
We investigate an evolution of the surface electronic state of the Bi1.5Sb0.5Te1.7Se1.3 single crystal, which is one of the most bulk insulating topological insulators, by examining terahertz light emitted from the sample surface upon the illumination of the near-infrared femtosecond laser pulses. We find that the surface state with a flat band bending can appear in the course of the natural maturation process of the surface state in an ambient air. Furthermore, we demonstrate that the evolution of the surface electronic state can be accelerated, decelerated, or even stopped by controlling environmental conditions to contain different amount of H2O, in particular.
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Ultrafast photocurrents at the surface of the three-dimensional topological insulator Bi 2Se 3. Nat Commun 2016; 7:13259. [PMID: 27796297 PMCID: PMC5095513 DOI: 10.1038/ncomms13259] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 09/16/2016] [Indexed: 12/26/2022] Open
Abstract
Three-dimensional topological insulators are fascinating materials with insulating bulk yet metallic surfaces that host highly mobile charge carriers with locked spin and momentum. Remarkably, surface currents with tunable direction and magnitude can be launched with tailored light beams. To better understand the underlying mechanisms, the current dynamics need to be resolved on the timescale of elementary scattering events (∼10 fs). Here, we excite and measure photocurrents in the model topological insulator Bi2Se3 with a time resolution of 20 fs by sampling the concomitantly emitted broadband terahertz (THz) electromagnetic field from 0.3 to 40 THz. Strikingly, the surface current response is dominated by an ultrafast charge transfer along the Se–Bi bonds. In contrast, photon-helicity-dependent photocurrents are found to be orders of magnitude smaller than expected from generation scenarios based on asymmetric depopulation of the Dirac cone. Our findings are of direct relevance for broadband optoelectronic devices based on topological-insulator surface currents. Surface currents in topological insulators can be controlled by light, but the underlying mechanisms are not well understood. Here, Braun et al. report an ultrafast shift photocurrent at the surface of Ca-doped Bi2Se3, whereas injection currents are much smaller than expected from asymmetric depopulation of the Dirac cone.
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