1
|
Haque E, Yin Y, Medhekar NV. Electron-phonon interactions at the topological edge states in single bilayer Bi(111). NANOSCALE 2024; 16:17442-17451. [PMID: 39219406 DOI: 10.1039/d4nr02172j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/04/2024]
Abstract
An intriguing feature of two-dimensional topological insulators is the topologically protected electronic edge state, which allows one-way carrier transport without backscattering. Although this feature has strong potential applications in lossless electronics, the ideal behavior of the edge states may be fragile due to electron-phonon (e-ph) interactions at room temperatures. Using density functional perturbation theory calculations for single bilayer Bi(111) as a prototypical 2D topological insulator, we show that e-ph scattering can be a significant source of backscattering at the topological edge states. We also show that e-ph interactions strongly correlate to the dispersions of the electronic edge states. In particular, the e-ph interactions increase significantly with temperature and are much stronger at the nonlinearly dispersed edge states of native edges compared to the linearly dispersed edge states of passivated edges, causing a significant energy dissipation in the temperature range of 200-400 K. Overall, we argue that the e-ph interactions can be a crucial factor at finite temperatures in controlling the electronic transport at the topologically protected edge states.
Collapse
Affiliation(s)
- Enamul Haque
- Department of Materials Science and Engineering, Monash University, Clayton, 3800 VIC, Australia.
- ARC Centre of Excellence in Future Low Energy Electronics Technologies (FLEET), Monash University, Clayton, 3800 VIC, Australia
| | - Yuefeng Yin
- Department of Materials Science and Engineering, Monash University, Clayton, 3800 VIC, Australia.
- ARC Centre of Excellence in Future Low Energy Electronics Technologies (FLEET), Monash University, Clayton, 3800 VIC, Australia
| | - Nikhil V Medhekar
- Department of Materials Science and Engineering, Monash University, Clayton, 3800 VIC, Australia.
- ARC Centre of Excellence in Future Low Energy Electronics Technologies (FLEET), Monash University, Clayton, 3800 VIC, Australia
| |
Collapse
|
2
|
Ahmad F, Kandpal K, Singh R, Kumar R, Kumar P. Aberrant photoelectric effect in the topological insulator/n-GaN heterojunction (Bi 2Te 3/n-GaN) under unpolarized illumination. NANOSCALE 2024; 16:604-613. [PMID: 38050855 DOI: 10.1039/d3nr03360k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
A topological insulator has a unique graphene-like Dirac cone conducting surface state, which is excellent for broadband absorption and photodetector applications. Experimental investigations on the Bi2Te3/n-GaN heterojunction exhibited an aberrant photoelectric effect under the influence of unpolarized light. Transport measurements of the Bi2Te3/n-GaN heterojunction revealed a negative photoconductance, with a sudden increase in resistance. This was consistent with the applied range of wavelength and power used for incident light while it was contrary to the usual gap-state transition model, which states that a negative conductance is due to the trapping of charge carriers. The observed aberrant photoelectric effect seen in Bi2Te3/n-GaN heterojunction devices was due to the polycrystalline nature of the Bi2Te3 topological insulator film, where the incident photon-induced bandgap in the Dirac cone surface state resulted in a negative photoelectric effect. This phenomenon opens the possibility for applications in highly sensitive photodetectors and non-volatile memories, along with employing the bandgap-opening concept in retinomorphic devices.
Collapse
Affiliation(s)
- Faizan Ahmad
- Electrical, Computer and Energy Engineering, Arizona State University, Tempe, AZ-85281, USA.
| | - Kavindra Kandpal
- Department of Electronics and Communication Engineering, IIIT-Allahabad, Prayagraj, 211012, India
| | - Roshani Singh
- Spintronics and Magnetic Materials Laboratory, Department of Applied Sciences, IIIT-Allahabad, Prayagraj, 211012, India.
| | - Rachana Kumar
- ASSIST Division, CSIR-Indian Institute of Toxicology Research, Lucknow, Uttar Pradesh, 226024, India
| | - Pramod Kumar
- Spintronics and Magnetic Materials Laboratory, Department of Applied Sciences, IIIT-Allahabad, Prayagraj, 211012, India.
| |
Collapse
|
3
|
Zhou JS, Xu RZ, Yu XQ, Cheng FJ, Zhao WX, Du X, Wang SZ, Zhang QQ, Gu X, He SM, Li YD, Ren MQ, Ma XC, Xue QK, Chen YL, Song CL, Yang LX. Evidence for Band Renormalizations in Strong-Coupling Superconducting Alkali-Fulleride Films. PHYSICAL REVIEW LETTERS 2023; 130:216004. [PMID: 37295091 DOI: 10.1103/physrevlett.130.216004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 02/06/2023] [Accepted: 04/17/2023] [Indexed: 06/12/2023]
Abstract
There has been a long-standing debate about the mechanism of the unusual superconductivity in alkali-intercalated fullerides. In this Letter, using high-resolution angle-resolved photoemission spectroscopy, we systematically investigate the electronic structures of superconducting K_{3}C_{60} thin films. We observe a dispersive energy band crossing the Fermi level with the occupied bandwidth of about 130 meV. The measured band structure shows prominent quasiparticle kinks and a replica band involving the Jahn-Teller active phonon modes, which reflects strong electron-phonon coupling in the system. The electron-phonon coupling constant is estimated to be about 1.2, which dominates the quasiparticle mass renormalization. Moreover, we observe an isotropic nodeless superconducting gap beyond the mean-field estimation (2Δ/k_{B}T_{c}≈5). Both the large electron-phonon coupling constant and large reduced superconducting gap suggest a strong-coupling superconductivity in K_{3}C_{60}, while the electronic correlation effect is suggested by the observation of a waterfall-like band dispersion and the small bandwidth compared with the effective Coulomb interaction. Our results not only directly visualize the crucial band structure but also provide important insights into the mechanism of the unusual superconductivity of fulleride compounds.
Collapse
Affiliation(s)
- J S Zhou
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - R Z Xu
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - X Q Yu
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - F J Cheng
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - W X Zhao
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - X Du
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - S Z Wang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - Q Q Zhang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - X Gu
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - S M He
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Y D Li
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - M Q Ren
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - X C Ma
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Q K Xue
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - Y L Chen
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
- School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai 201210, China
- ShanghaiTech Laboratory for Topological Physics, Shanghai 200031, China
| | - C L Song
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - L X Yang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| |
Collapse
|
4
|
Ruckhofer A, Benedek G, Bremholm M, Ernst WE, Tamtögl A. Observation of Dirac Charge-Density Waves in Bi 2Te 2Se. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:476. [PMID: 36770437 PMCID: PMC9919891 DOI: 10.3390/nano13030476] [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: 12/23/2022] [Revised: 01/18/2023] [Accepted: 01/19/2023] [Indexed: 06/18/2023]
Abstract
While parallel segments in the Fermi level contours, often found at the surfaces of topological insulators (TIs), would imply "strong" nesting conditions, the existence of charge-density waves (CDWs)-periodic modulations of the electron density-has not been verified up to now. Here, we report the observation of a CDW at the surface of the TI Bi2Te2Se(111), below ≈350K, by helium-atom scattering and, thus, experimental evidence for a CDW involving Dirac topological electrons. Deviations of the order parameter observed below 180K, and a low-temperature break of time reversal symmetry, suggest the onset of a spin-density wave with the same period as the CDW in the presence of a prominent electron-phonon interaction, originating from Rashba spin-orbit coupling.
Collapse
Affiliation(s)
- Adrian Ruckhofer
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
| | - Giorgio Benedek
- Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, Via R. Cozzi 55, 20125 Milano, Italy
- Donostia International Physics Center, University of the Basque Country, Paseo M. de Lardizabal 4, 20018 Donostia/San Sebastián, Spain
| | - Martin Bremholm
- Centre for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, 8000 Aarhus, Denmark
| | - Wolfgang E. Ernst
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
| | - Anton Tamtögl
- Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
| |
Collapse
|
5
|
Wiesner M, Koski K, Laitinen A, Manninen J, Zyuzin AA, Hakonen P. Electron-phonon coupling in copper intercalated Bi[Formula: see text]Se[Formula: see text]. Sci Rep 2022; 12:12097. [PMID: 35840599 PMCID: PMC9287361 DOI: 10.1038/s41598-022-15909-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 06/30/2022] [Indexed: 11/09/2022] Open
Abstract
We report charge and heat transport studies in copper-intercalated topological insulator Bi[Formula: see text]Se[Formula: see text] hybrid devices. Measured conductivity shows impact of quantum corrections, electron-electron and electron-phonon interactions. Our shot noise measurements reveal that heat flux displays a crossover between [Formula: see text] and [Formula: see text] with the increase of temperature. The results might be explained by a model of inelastic electron scattering on disorder, increasing the role of transverse acoustic phonons in the electron-phonon coupling process.
Collapse
Affiliation(s)
- Maciej Wiesner
- Faculty of Physics, Adam Mickiewicz University, Poznan, Poland
| | - Kristie Koski
- Department of Chemistry, University of California Davis, Davis, CA USA
| | - Antti Laitinen
- Low Temperature Laboratory, Department of Applied Physics, Aalto University, P.O. Box 15100, 00076 Aalto, Finland
- Department of Physics, Harvard University, Cambridge, MA 02138 USA
| | - Juuso Manninen
- Low Temperature Laboratory, Department of Applied Physics, Aalto University, P.O. Box 15100, 00076 Aalto, Finland
| | - Alexander A. Zyuzin
- Low Temperature Laboratory, Department of Applied Physics, Aalto University, P.O. Box 15100, 00076 Aalto, Finland
| | - Pertti Hakonen
- Low Temperature Laboratory, Department of Applied Physics, Aalto University, P.O. Box 15100, 00076 Aalto, Finland
| |
Collapse
|
6
|
Ghim M, Jhi SH. Kohn anomalies in topological insulator thin films: first-principles study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:265002. [PMID: 35405670 DOI: 10.1088/1361-648x/ac664a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 04/11/2022] [Indexed: 06/14/2023]
Abstract
Kohn anomaly is a non-smooth phonon softening induced by electron-phonon coupling in low-dimensional metals. Some measurements claimed that Kohn anomalies are present in topological materials due to the Dirac fermions in the bulk or in the surface. However, first-principles calculations have not reproduced the Kohn anomalies, especially, on the surface of topological insulators. It is still unclear about the origin of the controversy for the existence of the Kohn anomaly whether it is a numerical shortcoming or misinterpretation in measurement. In this study, we investigate the surface Kohn anomaly in two topological insulators Bi2Se3and SnSe using the state-of-the-art Wannier interpolation schemes. We find that Bi2Se3exhibits the Kohn anomaly but only in the bulk-like phonon modes by structural confinement along thec-axis. Interestingly, SnSe exhibits the surface Kohn anomaly in support of the experimental report on Pb0.7Sn0.3Se. We show that double Dirac cones in SnSe surface states are responsible for the Kohn anomaly, which is even enhanced if the subsurface states are partially occupied.
Collapse
Affiliation(s)
- Minjae Ghim
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Seung-Hoon Jhi
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| |
Collapse
|
7
|
Trzaskowska A, Mielcarek S, Wiesner M, Lombardi F, Mroz B. Dispersion of the surface phonons in semiconductor/topological insulator Si/Bi 2Te 3 heterostructure studied by high resolution Brillouin spectroscopy. ULTRASONICS 2021; 117:106526. [PMID: 34303926 DOI: 10.1016/j.ultras.2021.106526] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 06/11/2021] [Accepted: 07/16/2021] [Indexed: 06/13/2023]
Abstract
The dynamics and dispersion of surface phonons in heterostructure semiconductor/ topological insulator Si/Bi2Te3 was investigated using high resolution Brillouin light scattering method in the GHz frequency range. Both Rayleigh and Sezawa surface acoustic waves have been observed for wave vectors ranging from 0.006 to 0.023 nm-1. Anomaly in dispersion relations ω(q) for both surface waves were detected for the wave vector q = 0.016 nm-1. The finite element method (FEM) was used to simulate the observed shapes of ω(q) and to find the deformation profiles of surface acoustic waves. We attribute the observed changes to the coupling between low energy electrons and surface phonons. The coupling between helical Dirac states and surface phonons is discussed in the frame of accessible theoretical models.
Collapse
Affiliation(s)
- A Trzaskowska
- Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznańskiego 2, 61-614 Poznan, Poland.
| | - S Mielcarek
- Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznańskiego 2, 61-614 Poznan, Poland
| | - M Wiesner
- Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznańskiego 2, 61-614 Poznan, Poland
| | - F Lombardi
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96, Göteborg, Sweden
| | - B Mroz
- Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznańskiego 2, 61-614 Poznan, Poland
| |
Collapse
|
8
|
Kiphart D, Harkavyi Y, Balin K, Szade J, Mróz B, Kuświk P, Jurga S, Wiesner M. Investigations of proximity-induced superconductivity in the topological insulator Bi 2Te 3 by microRaman spectroscopy. Sci Rep 2021; 11:22980. [PMID: 34837028 PMCID: PMC8626455 DOI: 10.1038/s41598-021-02475-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 11/01/2021] [Indexed: 11/12/2022] Open
Abstract
We used the topological insulator (TI) Bi2Te3 and a high-temperature superconductor (HTSC) hybrid device for investigations of proximity-induced superconductivity (PS) in the TI. Application of the superconductor YBa2Cu3O7-δ (YBCO) enabled us to access higher temperature and energy scales for this phenomenon. The HTSC in the hybrid device exhibits emergence of a pseudogap state for T > Tc that converts into a superconducting state with a reduced gap for T < Tc. The conversion process has been reflected in Raman spectra collected from the TI. Complementary charge transport experiments revealed emergence of the proximity-induced superconducting gap in the TI and the reduced superconducting gap in the HTSC, but no signature of the pseudogap. This allowed us to conclude that Raman spectroscopy reveals formation of the pseudogap state but cannot distinguish the proximity-induced superconducting state in the TI from the superconducting state in the HTSC characterised by the reduced gap. Results of our experiments have shown that Raman spectroscopy is a complementary technique to classic charge transport experiments and is a powerful tool for investigation of the proximity-induced superconductivity in the Bi2Te3.
Collapse
Affiliation(s)
- D Kiphart
- Adam Mickiewicz University, Faculty of Physics, Uniwersytetu Poznanskiego 2, 61-614, Poznan, Poland
| | - Y Harkavyi
- Adam Mickiewicz University, Faculty of Physics, Uniwersytetu Poznanskiego 2, 61-614, Poznan, Poland
| | - K Balin
- A. Chełkowski Institute of Physics and Silesian Center for Education and Interdisciplinary Research, University of Silesia, 75 Pułku Piechoty 1A, 41-500, Chorzow, Poland
| | - J Szade
- A. Chełkowski Institute of Physics and Silesian Center for Education and Interdisciplinary Research, University of Silesia, 75 Pułku Piechoty 1A, 41-500, Chorzow, Poland
| | - B Mróz
- Adam Mickiewicz University, Faculty of Physics, Uniwersytetu Poznanskiego 2, 61-614, Poznan, Poland
| | - P Kuświk
- Institute of Molecular Physics, Polish Academy of Sciences, ul. Smoluchowskiego 17, 60-179, Poznan, Poland
| | - S Jurga
- The NanoBioMedical Centre, Adam Mickiewicz University, Wszechnicy Piastowskiej 3, 61-614, Poznan, Poland
| | - M Wiesner
- Adam Mickiewicz University, Faculty of Physics, Uniwersytetu Poznanskiego 2, 61-614, Poznan, Poland.
| |
Collapse
|
9
|
Choe J, Lujan D, Rodriguez-Vega M, Ye Z, Leonardo A, Quan J, Nunley TN, Chang LJ, Lee SF, Yan J, Fiete GA, He R, Li X. Electron-Phonon and Spin-Lattice Coupling in Atomically Thin Layers of MnBi 2Te 4. NANO LETTERS 2021; 21:6139-6145. [PMID: 34252281 DOI: 10.1021/acs.nanolett.1c01719] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
MnBi2Te4 represents a new class of magnetic topological insulators in which novel quantum phases emerge at temperatures higher than those found in magnetically doped thin films. Here, we investigate how couplings between electron, spin, and lattice are manifested in the phonon spectra of few-septuple-layer thick MnBi2Te4. After categorizing phonon modes by their symmetries, we study the systematic changes in frequency, line width, and line shape of a spectrally isolated A1g mode. The electron-phonon coupling increases in thinner flakes as manifested in a broader phonon line width, which is likely due to changes of the electron density of states. In 4- and 5-septuple thick samples, the onset of magnetic order below the Néel temperature is concurrent with a transition to an insulating state. We observe signatures of a reduced electron-phonon scattering across this transition as reflected in the reduced Fano parameter. Finally, spin-lattice coupling is measured and modeled from temperature-dependent phonon frequency.
Collapse
Affiliation(s)
- Jeongheon Choe
- Department of Physics, Center of Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712 United States
- Center for Dynamics and Control of Materials, The University of Texas at Austin, Austin, Texas 78712, United States
| | - David Lujan
- Department of Physics, Center of Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712 United States
- Center for Dynamics and Control of Materials, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Martin Rodriguez-Vega
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Zhipeng Ye
- Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409, United States
| | - Aritz Leonardo
- Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian, Spain
- Department of Physics, University of the Basque Country UPV/EHU, 48940 Leioa, Spain
| | - Jiamin Quan
- Department of Physics, Center of Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712 United States
| | - T Nathan Nunley
- Department of Physics, Center of Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712 United States
| | - Liang-Juan Chang
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712 United States
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Shang-Fan Lee
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Jiaqiang Yan
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Gregory A Fiete
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, United States
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Rui He
- Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409, United States
| | - Xiaoqin Li
- Department of Physics, Center of Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712 United States
- Center for Dynamics and Control of Materials, The University of Texas at Austin, Austin, Texas 78712, United States
- Texas Materials Institute, University of Texas at Austin, Austin, Texas 78712, United States
| |
Collapse
|
10
|
Holst B, Alexandrowicz G, Avidor N, Benedek G, Bracco G, Ernst WE, Farías D, Jardine AP, Lefmann K, Manson JR, Marquardt R, Artés SM, Sibener SJ, Wells JW, Tamtögl A, Allison W. Material properties particularly suited to be measured with helium scattering: selected examples from 2D materials, van der Waals heterostructures, glassy materials, catalytic substrates, topological insulators and superconducting radio frequency materials. Phys Chem Chem Phys 2021; 23:7653-7672. [PMID: 33625410 DOI: 10.1039/d0cp05833e] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Helium Atom Scattering (HAS) and Helium Spin-Echo scattering (HeSE), together helium scattering, are well established, but non-commercial surface science techniques. They are characterised by the beam inertness and very low beam energy (<0.1 eV) which allows essentially all materials and adsorbates, including fragile and/or insulating materials and light adsorbates such as hydrogen to be investigated on the atomic scale. At present there only exist an estimated less than 15 helium and helium spin-echo scattering instruments in total, spread across the world. This means that up till now the techniques have not been readily available for a broad scientific community. Efforts are ongoing to change this by establishing a central helium scattering facility, possibly in connection with a neutron or synchrotron facility. In this context it is important to clarify what information can be obtained from helium scattering that cannot be obtained with other surface science techniques. Here we present a non-exclusive overview of a range of material properties particularly suited to be measured with helium scattering: (i) high precision, direct measurements of bending rigidity and substrate coupling strength of a range of 2D materials and van der Waals heterostructures as a function of temperature, (ii) direct measurements of the electron-phonon coupling constant λ exclusively in the low energy range (<0.1 eV, tuneable) for 2D materials and van der Waals heterostructures (iii) direct measurements of the surface boson peak in glassy materials, (iv) aspects of polymer chain surface dynamics under nano-confinement (v) certain aspects of nanoscale surface topography, (vi) central properties of surface dynamics and surface diffusion of adsorbates (HeSE) and (vii) two specific science case examples - topological insulators and superconducting radio frequency materials, illustrating how combined HAS and HeSE are necessary to understand the properties of quantum materials. The paper finishes with (viii) examples of molecular surface scattering experiments and other atom surface scattering experiments which can be performed using HAS and HeSE instruments.
Collapse
Affiliation(s)
- Bodil Holst
- Department of Physics and Technology, University of Bergen, Allegaten 55, 5007 Bergen, Norway.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Imaging current distribution in a topological insulator Bi 2Se 3 in the presence of competing surface and bulk contributions to conductivity. Sci Rep 2021; 11:7445. [PMID: 33811220 PMCID: PMC8018954 DOI: 10.1038/s41598-021-86706-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 03/15/2021] [Indexed: 11/10/2022] Open
Abstract
Two-dimensional (2D) topological surface states in a three-dimensional topological insulator (TI) should produce uniform 2D surface current distribution. However, our transport current imaging studies on Bi2Se3 thin film reveal non-uniform current sheet flow at 15 K with strong edge current flow. This is consistent with other imaging studies on thin films of Bi2Se3. In contrast to strong edge current flow in thin films, in single crystal of Bi2Se3 at 15 K our current imaging studies show the presence of 3.6 nm thick uniform 2D sheet current flow. Above 70 K, this uniform 2D sheet current sheet begins to disintegrate into a spatially non-uniform flow. The flow becomes patchy with regions having high and low current density. The area fraction of the patches with high current density rapidly decreases at temperatures above 70 K, with a temperature dependence of the form \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$1/\left| {T - 70} \right|^{0.35}$$\end{document}1/T-700.35. The temperature scale of 70 K coincides with the onset of bulk conductivity in the crystal due to electron doping by selenium vacancy clusters in Bi2Se3. Thus our results show a temperature dependent competition between surface and bulk conductivity produces a temperature dependent variation in uniformity of current flow in the topological insulator.
Collapse
|
12
|
Zhou J, Shin HD, Chen K, Song B, Duncan RA, Xu Q, Maznev AA, Nelson KA, Chen G. Direct observation of large electron-phonon interaction effect on phonon heat transport. Nat Commun 2020; 11:6040. [PMID: 33247148 PMCID: PMC7695728 DOI: 10.1038/s41467-020-19938-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 11/02/2020] [Indexed: 11/29/2022] Open
Abstract
As a foundational concept in many-body physics, electron-phonon interaction is essential to understanding and manipulating charge and energy flow in various electronic, photonic, and energy conversion devices. While much progress has been made in uncovering how phonons affect electron dynamics, it remains a challenge to directly observe the impact of electrons on phonon transport, especially at environmental temperatures. Here, we probe the effect of charge carriers on phonon heat transport at room temperature, using a modified transient thermal grating technique. By optically exciting electron-hole pairs in a crystalline silicon membrane, we single out the effect of the phonon-carrier interaction. The enhanced phonon scattering by photoexcited free carriers results in a substantial reduction in thermal conductivity on a nanosecond timescale. Our study provides direct experimental evidence of the elusive role of electron-phonon interaction in phonon heat transport, which is important for understanding heat conduction in doped semiconductors. We also highlight the possibility of using light to dynamically control thermal transport via electron-phonon coupling.
Collapse
Affiliation(s)
- Jiawei Zhou
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Hyun D Shin
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Ke Chen
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- School of Physics, Sun Yat-sen University, 510275, Guangzhou, China
| | - Bai Song
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- Department of Energy and Resources Engineering, and Beijing Innovation Center for Engineering Science and Advanced Technology, Peking University, 100871, Beijing, China
| | - Ryan A Duncan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Qian Xu
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Alexei A Maznev
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Keith A Nelson
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Gang Chen
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
| |
Collapse
|
13
|
Benedek G, Miret-Artés S, Manson JR, Ruckhofer A, Ernst WE, Tamtögl A. Origin of the Electron-Phonon Interaction of Topological Semimetal Surfaces Measured with Helium Atom Scattering. J Phys Chem Lett 2020; 11:1927-1933. [PMID: 32032492 PMCID: PMC7061329 DOI: 10.1021/acs.jpclett.9b03829] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 02/07/2020] [Indexed: 06/10/2023]
Abstract
He atom scattering has been demonstrated to be a sensitive probe of the electron-phonon interaction parameter λ at metal and metal-overlayer surfaces. Here it is shown that the theory linking λ to the thermal attenuation of atom scattering spectra (the Debye-Waller factor) can be applied to topological semimetal surfaces, such as the quasi-one-dimensional charge-density-wave system Bi(114) and the layered pnictogen chalcogenides. The electron-phonon coupling, as determined for several topological insulators belonging to the class of bismuth chalcogenides, suggests a dominant contribution of the surface quantum well states over the Dirac electrons in terms of λ.
Collapse
Affiliation(s)
- Giorgio Benedek
- Donostia
International Physics Center (DIPC), Paseo Manuel de Lardizabal, 4, 20018 Donostia-San Sebastian, Spain
- Dipartimento
di Scienza dei Materiali, Università
di Milano-Bicocca, Via Cozzi 53, 20125 Milano, Italy
| | - Salvador Miret-Artés
- Donostia
International Physics Center (DIPC), Paseo Manuel de Lardizabal, 4, 20018 Donostia-San Sebastian, Spain
- Instituto
de Física Fundamental, Consejo Superior
de Investigaciones Científicas, Serrano 123, 28006 Madrid, Spain
| | - J. R. Manson
- Donostia
International Physics Center (DIPC), Paseo Manuel de Lardizabal, 4, 20018 Donostia-San Sebastian, Spain
- Department
of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634, United States
| | - Adrian Ruckhofer
- Institute
of Experimental Physics, Graz University
of Technology, 8010 Graz, Austria
| | - Wolfgang E. Ernst
- Institute
of Experimental Physics, Graz University
of Technology, 8010 Graz, Austria
| | - Anton Tamtögl
- Institute
of Experimental Physics, Graz University
of Technology, 8010 Graz, Austria
| |
Collapse
|
14
|
Abstract
The phenomenon of superconductivity occurs in the phase space of three principal parameters: temperature T, magnetic field B, and current density j. The critical temperature T c is one of the first parameters that is measured and in a certain way defines the superconductor. From the practical applications point of view, of equal importance is the upper critical magnetic field B c 2 and conventional critical current density j c (above which the system begins to show resistance without entering the normal state). However, a seldom-measured parameter, the depairing current density j d , holds the same fundamental importance as T c and B c 2 , in that it defines a boundary between the superconducting and normal states. A study of j d sheds unique light on other important characteristics of the superconducting state such as the superfluid density and the nature of the normal state below T c , information that can play a key role in better understanding newly-discovered superconducting materials. From a measurement perspective, the extremely high values of j d make it difficult to measure, which is the reason why it is seldom measured. Here, we will review the fundamentals of current-induced depairing and the fast-pulsed current technique that facilitates its measurement and discuss the results of its application to the topological-insulator/chalcogenide interfacial superconducting system.
Collapse
|
15
|
Plucinski L. Band structure engineering in 3D topological insulators. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:183001. [PMID: 30731442 DOI: 10.1088/1361-648x/ab052c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The discovery of novel topological phases has revolutionized the way we think about electronic matter. Topologically protected states have been demonstrated for many materials, however, creating materials that exhibit desired properties often remains a challenge. For example, one of the key challenges in three dimensional topological insulators has been the realization of insulating bulk, such that the unique properties of surface states could be fully employed in electron transport applications. Further challenges are in creating materials that simultaneously exhibit states protected by various symmetries on their different surfaces, inducing magnetic exchange coupling into the topological materials, as well as potentially creating non-trivial transient electronic states. This review presents theoretical concepts and a selection of experimental results from the point view of a spectroscopist, and as such might be useful for physicists who want to get familiar with the key concepts in a self-contained form with formalism reduced to readily understandable concepts.
Collapse
Affiliation(s)
- L Plucinski
- Peter Grünberg Institut PGI-6, Forschungszentrum Jülich, D-52425 Jülich, Germany. Jülich Aachen Research Alliance-Fundamentals of Future Information Technologies (JARA-FIT), 52425 Jülich, Germany
| |
Collapse
|
16
|
Surface State Dynamics of Topological Insulators Investigated by Femtosecond Time- and Angle-Resolved Photoemission Spectroscopy. APPLIED SCIENCES-BASEL 2018. [DOI: 10.3390/app8050694] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
|
17
|
Luo Z, Tian J, Huang S, Srinivasan M, Maassen J, Chen YP, Xu X. Large Enhancement of Thermal Conductivity and Lorenz Number in Topological Insulator Thin Films. ACS NANO 2018; 12:1120-1127. [PMID: 29361229 DOI: 10.1021/acsnano.7b06430] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Topological insulators (TI) have attracted extensive research effort due to their insulating bulk states but conducting surface states. However, investigation and understanding of thermal transport in topological insulators, particularly the effect of surface states, are lacking. In this work, we studied thickness-dependent in-plane thermal and electrical conductivity of Bi2Te2Se TI thin films. A large enhancement in both thermal and electrical conductivity was observed for films with thicknesses below 20 nm, which is attributed to the surface states and bulk-insulating nature of these films. Moreover, a surface Lorenz number much larger than the Sommerfeld value was found. Systematic transport measurements indicated that the Fermi surface is located near the charge neutrality point (CNP) when the film thickness is below 20 nm. Possible reasons for the large Lorenz number include electrical and thermal current decoupling in the surface state Dirac fluid, and bipolar diffusion transport. A simple computational model indicates that the surface states and bipolar diffusion indeed can lead to enhanced electrical and thermal transport and a large Lorenz number.
Collapse
Affiliation(s)
| | | | | | | | - Jesse Maassen
- Department of Physics and Atmospheric Science, Dalhousie University , Halifax, Nova Scotia B3H 4R2, Canada
| | | | | |
Collapse
|
18
|
Zhang S, Kronast F, van der Laan G, Hesjedal T. Real-Space Observation of Skyrmionium in a Ferromagnet-Magnetic Topological Insulator Heterostructure. NANO LETTERS 2018; 18:1057-1063. [PMID: 29363315 DOI: 10.1021/acs.nanolett.7b04537] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The combination of topological insulators, that is, bulk insulators with gapless, topologically protected surface states, with magnetic order is a love-hate relationship that can unlock new quantum states and exotic physical phenomena, such as the quantum anomalous Hall effect and axion electrodynamics. Moreover, the unusual coupling between topological insulators and ferromagnets can also result in the formation of topological spin textures in the ferromagnetic layer. Skyrmions are topologically protected magnetization swirls that are promising candidates for spintronics memory carriers. Here, we report on the observation of skyrmionium in thin ferromagnetic films coupled to a magnetic topological insulator. The occurrence of skyrmionium, which appears as a soliton composed of two skyrmions with opposite winding numbers, is tied to the ferromagnetic state of the topological insulator. Our work presents a new combination of two important classes of topological materials and may open the door to new topologically inspired information-storage concepts in the future.
Collapse
Affiliation(s)
- Shilei Zhang
- Clarendon Laboratory, Department of Physics, University of Oxford , Parks Road, Oxford, OX1 3PU, United Kingdom
| | - Florian Kronast
- Helmholtz-Zentrum Berlin für Materialien und Energie , Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - Gerrit van der Laan
- Magnetic Spectroscopy Group , Diamond Light Source, Didcot, OX11 0DE, United Kingdom
| | - Thorsten Hesjedal
- Clarendon Laboratory, Department of Physics, University of Oxford , Parks Road, Oxford, OX1 3PU, United Kingdom
| |
Collapse
|
19
|
The electron-phonon interaction at deep Bi 2 Te 3-semiconductor interfaces from Brillouin light scattering. Sci Rep 2017; 7:16449. [PMID: 29180657 PMCID: PMC5703879 DOI: 10.1038/s41598-017-16313-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 10/25/2017] [Indexed: 11/08/2022] Open
Abstract
It is shown that the electron-phonon interaction at a conducting interface between a topological insulator thin film and a semiconductor substrate can be directly probed by means of high-resolution Brillouin light scattering (BLS). The observation of Kohn anomalies in the surface phonon dispersion curves of a 50 nm thick Bi2Te3 film on GaAs, besides demonstrating important electron-phonon coupling effects in the GHz frequency domain, shows that information on deep interface electrons can be obtained by tuning the penetration depth of optically-generated surface phonons so as to selectively probe the interface region, as in a sort of quantum sonar.
Collapse
|
20
|
Wang XB, Cheng L, Wu Y, Zhu DP, Wang L, Zhu JX, Yang H, Chia EEM. Topological-insulator-based terahertz modulator. Sci Rep 2017; 7:13486. [PMID: 29044164 PMCID: PMC5647436 DOI: 10.1038/s41598-017-13701-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 09/27/2017] [Indexed: 11/30/2022] Open
Abstract
Three dimensional topological insulators, as a new phase of quantum matters, are characterized by an insulating gap in the bulk and a metallic state on the surface. Particularly, most of the topological insulators have narrow band gaps, and hence have promising applications in the area of terahertz optoelectronics. In this work, we experimentally demonstrate an electronically-tunable terahertz intensity modulator based on Bi1:5Sb0:5Te1:8Se1:2 single crystal, one of the most insulating topological insulators. A relative frequency-independent modulation depth of ~62% over a wide frequency range from 0.3 to 1.4 THz has been achieved at room temperature, by applying a bias current of 100 mA. The modulation in the low current regime can be further enhanced at low temperature. We propose that the extraordinarily large modulation is a consequence of thermally-activated carrier absorption in the semiconducting bulk states. Our work provides a new application of topological insulators for terahertz technology.
Collapse
Affiliation(s)
- X B Wang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - L Cheng
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Y Wu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - D P Zhu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - L Wang
- School of Applied Sciences, RMIT University, Melbourne, Victoria, 3001, Australia
| | - Jian-Xin Zhu
- Theoretical Division and Center for Integrated Nanotechnologies, Los Alamos National Laboratory, New Mexico, 87545, USA
| | - 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, Singapore, 637371, Singapore.
| |
Collapse
|
21
|
Martínez-Velarte MC, Kretz B, Moro-Lagares M, Aguirre MH, Riedemann TM, Lograsso TA, Morellón L, Ibarra MR, Garcia-Lekue A, Serrate D. Chemical Disorder in Topological Insulators: A Route to Magnetism Tolerant Topological Surface States. NANO LETTERS 2017; 17:4047-4054. [PMID: 28605918 DOI: 10.1021/acs.nanolett.7b00311] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We show that the chemical inhomogeneity in ternary three-dimensional topological insulators preserves the topological spin texture of their surface states against a net surface magnetization. The spin texture is that of a Dirac cone with helical spin structure in the reciprocal space, which gives rise to spin-polarized and dissipation-less charge currents. Thanks to the nontrivial topology of the bulk electronic structure, this spin texture is robust against most types of surface defects. However, magnetic perturbations break the time-reversal symmetry, enabling magnetic scattering and loss of spin coherence of the charge carriers. This intrinsic incompatibility precludes the design of magnetoelectronic devices based on the coupling between magnetic materials and topological surface states. We demonstrate that the magnetization coming from individual Co atoms deposited on the surface can disrupt the spin coherence of the carriers in the archetypal topological insulator Bi2Te3, while in Bi2Se2Te the spin texture remains unperturbed. This is concluded from the observation of elastic backscattering events in quasiparticle interference patterns obtained by scanning tunneling spectroscopy. The mechanism responsible for the protection is investigated by energy resolved spectroscopy and ab initio calculations, and it is ascribed to the distorted adsorption geometry of localized magnetic moments due to Se-Te disorder, which suppresses the Co hybridization with the surface states.
Collapse
Affiliation(s)
- M Carmen Martínez-Velarte
- Instituto de Nanociencia de Aragón (INA) & Laboratorio de Microscopias Avanzadas (LMA), University of Zaragoza , 50018 Zaragoza, Spain
- Department of Condensed Matter Physics, University of Zaragoza , 50009 Zaragoza, Spain
- Fundación Instituto de Nanociencia de Aragón (FINA) , 50018 Zaragoza, Spain
| | - Bernhard Kretz
- Donostia International Physics Center (DIPC) , E-20018 San Sebastián, Spain
| | - María Moro-Lagares
- Instituto de Nanociencia de Aragón (INA) & Laboratorio de Microscopias Avanzadas (LMA), University of Zaragoza , 50018 Zaragoza, Spain
- Department of Condensed Matter Physics, University of Zaragoza , 50009 Zaragoza, Spain
| | - Myriam H Aguirre
- Instituto de Nanociencia de Aragón (INA) & Laboratorio de Microscopias Avanzadas (LMA), University of Zaragoza , 50018 Zaragoza, Spain
- Department of Condensed Matter Physics, University of Zaragoza , 50009 Zaragoza, Spain
- Fundación Instituto de Nanociencia de Aragón (FINA) , 50018 Zaragoza, Spain
| | - Trevor M Riedemann
- Ames Laboratory , U.S. Department of Energy, Ames, Iowa 50011, United States
| | - Thomas A Lograsso
- Ames Laboratory , U.S. Department of Energy, Ames, Iowa 50011, United States
- Department of Materials Sciences & Engineering, Iowa State University , Ames, Iowa 50011 United States
| | - Luis Morellón
- Instituto de Nanociencia de Aragón (INA) & Laboratorio de Microscopias Avanzadas (LMA), University of Zaragoza , 50018 Zaragoza, Spain
- Department of Condensed Matter Physics, University of Zaragoza , 50009 Zaragoza, Spain
- Fundación Instituto de Nanociencia de Aragón (FINA) , 50018 Zaragoza, Spain
| | - M Ricardo Ibarra
- Instituto de Nanociencia de Aragón (INA) & Laboratorio de Microscopias Avanzadas (LMA), University of Zaragoza , 50018 Zaragoza, Spain
- Department of Condensed Matter Physics, University of Zaragoza , 50009 Zaragoza, Spain
- Fundación Instituto de Nanociencia de Aragón (FINA) , 50018 Zaragoza, Spain
| | - Arán Garcia-Lekue
- Donostia International Physics Center (DIPC) , E-20018 San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science , E-48011 Bilbao, Spain
| | - David Serrate
- Instituto de Nanociencia de Aragón (INA) & Laboratorio de Microscopias Avanzadas (LMA), University of Zaragoza , 50018 Zaragoza, Spain
- Department of Condensed Matter Physics, University of Zaragoza , 50009 Zaragoza, Spain
- Fundación Instituto de Nanociencia de Aragón (FINA) , 50018 Zaragoza, Spain
| |
Collapse
|
22
|
Electron-phonon coupling in topological surface states: The role of polar optical modes. Sci Rep 2017; 7:1095. [PMID: 28439125 PMCID: PMC5430646 DOI: 10.1038/s41598-017-01128-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 03/27/2017] [Indexed: 11/10/2022] Open
Abstract
The use of topological edge states for spintronic applications could be severely hampered by limited lifetimes due to intrinsic many-body interactions, in particular electron-phonon coupling. Previous works to determine the intrinsic coupling strength did not provide a coherent answer. Here, the electron-phonon interaction in the metallic surface state of 3D topological insulators is revised within a first principles framework. For the archetypical cases of Bi2Se3 and Bi2Te3, we find an overall weak coupling constant of less than 0.15, but with a characteristic energy dependence. Derived electronic self-energies compare favorably with previous angle-resolved photoemission spectroscopy results. The prevailing coupling is carried by optical modes of polar character, which is weakly screened by the metallic surface state and can be reduced by doping into bulk bands. We do not find any indication of a strong coupling to the A1g mode or the presence of a Kohn anomaly in the surface phonon spectrum. The weak intrinsic electron-phonon coupling guarantees long-lived quasiparticles at elevated temperatures.
Collapse
|
23
|
|
24
|
Liao B, Maznev AA, Nelson KA, Chen G. Photo-excited charge carriers suppress sub-terahertz phonon mode in silicon at room temperature. Nat Commun 2016; 7:13174. [PMID: 27731406 PMCID: PMC5064017 DOI: 10.1038/ncomms13174] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 09/05/2016] [Indexed: 11/09/2022] Open
Abstract
There is a growing interest in the mode-by-mode understanding of electron and phonon transport for improving energy conversion technologies, such as thermoelectrics and photovoltaics. Whereas remarkable progress has been made in probing phonon-phonon interactions, it has been a challenge to directly measure electron-phonon interactions at the single-mode level, especially their effect on phonon transport above cryogenic temperatures. Here we use three-pulse photoacoustic spectroscopy to investigate the damping of a single sub-terahertz coherent phonon mode by free charge carriers in silicon at room temperature. Building on conventional pump-probe photoacoustic spectroscopy, we introduce an additional laser pulse to optically generate charge carriers, and carefully design temporal sequence of the three pulses to unambiguously quantify the scattering rate of a single-phonon mode due to the electron-phonon interaction. Our results confirm predictions from first-principles simulations and indicate the importance of the often-neglected effect of electron-phonon interaction on phonon transport in doped semiconductors.
Collapse
Affiliation(s)
- Bolin Liao
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - A. A. Maznev
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Keith A. Nelson
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Gang Chen
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| |
Collapse
|
25
|
Xu N, Ding H, Shi M. Spin- and angle-resolved photoemission on the topological Kondo insulator candidate: SmB6. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:363001. [PMID: 27391865 DOI: 10.1088/0953-8984/28/36/363001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Topological Kondo insulators are a new class of topological insulators in which metallic surface states protected by topological invariants reside in the bulk band gap at low temperatures. Unlike other 3D topological insulators, a truly insulating bulk state, which is critical for potential applications in next-generation electronic devices, is guaranteed by many-body effects in the topological Kondo insulator. Furthermore, the system has strong electron correlations that can serve as a testbed for interacting topological theories. This topical review focuses on recent advances in the study of SmB6, the most promising candidate for a topological Kondo insulator, from the perspective of spin- and angle-resolved photoemission spectroscopy with highlights of some important transport results.
Collapse
Affiliation(s)
- Nan Xu
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland. Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | | | | |
Collapse
|
26
|
Siroki G, Lee D, Haynes PD, Giannini V. Single-electron induced surface plasmons on a topological nanoparticle. Nat Commun 2016; 7:12375. [PMID: 27491515 PMCID: PMC4980453 DOI: 10.1038/ncomms12375] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 06/27/2016] [Indexed: 11/13/2022] Open
Abstract
It is rarely the case that a single electron affects the behaviour of several hundred thousands of atoms. Here we demonstrate a phenomenon where this happens. The key role is played by topological insulators-materials that have surface states protected by time-reversal symmetry. Such states are delocalized over the surface and are immune to its imperfections in contrast to ordinary insulators. For topological insulators, the effects of these surface states will be more strongly pronounced in the case of nanoparticles. Here we show that under the influence of light a single electron in a topologically protected surface state creates a surface charge density similar to a plasmon in a metallic nanoparticle. Such an electron can act as a screening layer, which suppresses absorption inside the particle. In addition, it can couple phonons and light, giving rise to a previously unreported topological particle polariton mode. These effects may be useful in the areas of plasmonics, cavity electrodynamics and quantum information.
Collapse
Affiliation(s)
- G. Siroki
- Department of Physics, Imperial College London, Prince Consort Road London, London SW7 2AZ, UK
| | - D.K.K. Lee
- Department of Physics, Imperial College London, Prince Consort Road London, London SW7 2AZ, UK
| | - P. D. Haynes
- Department of Physics, Imperial College London, Prince Consort Road London, London SW7 2AZ, UK
- Department of Materials, Imperial College London, London SW7 2AZ, UK
| | - V. Giannini
- Department of Physics, Imperial College London, Prince Consort Road London, London SW7 2AZ, UK
| |
Collapse
|
27
|
Dordevic SV, Foster GM, Wolf MS, Stojilovic N, Lei H, Petrovic C, Chen Z, Li ZQ, Tung LC. Fano q-reversal in topological insulator Bi2Se3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:165602. [PMID: 27001951 DOI: 10.1088/0953-8984/28/16/165602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We studied the magneto-optical response of a canonical topological insulator Bi2Se3 with the goal of addressing a controversial issue of electron-phonon coupling. Magnetic-field induced modifications of reflectance are very pronounced in the infrared part of the spectrum, indicating strong electron-phonon coupling. This coupling causes an asymmetric line-shape of the 60 cm(-1) phonon mode, and is analyzed within the Fano formalism. The analysis reveals that the Fano asymmetry parameter (q) changes sign when the cyclotron resonance is degenerate with the phonon mode. To the best of our knowledge this is the first example of magnetic field driven q-reversal.
Collapse
Affiliation(s)
- S V Dordevic
- Department of Physics, The University of Akron, Akron, OH 44325, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Electronic structure and relaxation dynamics in a superconducting topological material. Sci Rep 2016; 6:22557. [PMID: 26936229 PMCID: PMC4776114 DOI: 10.1038/srep22557] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 02/02/2016] [Indexed: 01/23/2023] Open
Abstract
Topological superconductors host new states of quantum matter which show a pairing gap in the bulk and gapless surface states providing a platform to realize Majorana fermions. Recently, alkaline-earth metal Sr intercalated Bi2Se3 has been reported to show superconductivity with a Tc ~ 3 K and a large shielding fraction. Here we report systematic normal state electronic structure studies of Sr0.06Bi2Se3 (Tc ~ 2.5 K) by performing photoemission spectroscopy. Using angle-resolved photoemission spectroscopy (ARPES), we observe a quantum well confined two-dimensional (2D) state coexisting with a topological surface state in Sr0.06Bi2Se3. Furthermore, our time-resolved ARPES reveals the relaxation dynamics showing different decay mechanism between the excited topological surface states and the two-dimensional states. Our experimental observation is understood by considering the intra-band scattering for topological surface states and an additional electron phonon scattering for the 2D states, which is responsible for the superconductivity. Our first-principles calculations agree with the more effective scattering and a shorter lifetime of the 2D states. Our results will be helpful in understanding low temperature superconducting states of these topological materials.
Collapse
|
29
|
Kogar A, Vig S, Thaler A, Wong MH, Xiao Y, Reig-I-Plessis D, Cho GY, Valla T, Pan Z, Schneeloch J, Zhong R, Gu GD, Hughes TL, MacDougall GJ, Chiang TC, Abbamonte P. Surface Collective Modes in the Topological Insulators Bi_{2}Se_{3} and Bi_{0.5}Sb_{1.5}Te_{3-x}Se_{x}. PHYSICAL REVIEW LETTERS 2015; 115:257402. [PMID: 26722943 DOI: 10.1103/physrevlett.115.257402] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Indexed: 06/05/2023]
Abstract
We used low-energy, momentum-resolved inelastic electron scattering to study surface collective modes of the three-dimensional topological insulators Bi_{2}Se_{3} and Bi_{0.5}Sb_{1.5}Te_{3-x}Se_{x}. Our goal was to identify the "spin plasmon" predicted by Raghu and co-workers [Phys. Rev. Lett. 104, 116401 (2010)]. Instead, we found that the primary collective mode is a surface plasmon arising from the bulk, free carriers in these materials. This excitation dominates the spectral weight in the bosonic function of the surface χ^{"}(q,ω) at THz energy scales, and is the most likely origin of a quasiparticle dispersion kink observed in previous photoemission experiments. Our study suggests that the spin plasmon may mix with this other surface mode, calling for a more nuanced understanding of optical experiments in which the spin plasmon is reported to play a role.
Collapse
Affiliation(s)
- A Kogar
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - S Vig
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - A Thaler
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - M H Wong
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - Y Xiao
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - D Reig-I-Plessis
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - G Y Cho
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
| | - T Valla
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Z Pan
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - J Schneeloch
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - R Zhong
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - G D Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - T L Hughes
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - G J MacDougall
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - T-C Chiang
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - P Abbamonte
- Department of Physics and Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| |
Collapse
|
30
|
Dankert A, Geurs J, Kamalakar MV, Charpentier S, Dash SP. Room Temperature Electrical Detection of Spin Polarized Currents in Topological Insulators. NANO LETTERS 2015; 15:7976-7981. [PMID: 26560203 DOI: 10.1021/acs.nanolett.5b03080] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Topological insulators (TIs) are a new class of quantum materials that exhibit a current-induced spin polarization due to spin-momentum locking of massless Dirac Fermions in their surface states. This helical spin polarization in three-dimensional (3D) TIs has been observed using photoemission spectroscopy up to room temperatures. Recently, spin polarized surface currents in 3D TIs were detected electrically by potentiometric measurements using ferromagnetic detector contacts. However, these electric measurements are so far limited to cryogenic temperatures. Here we report the room temperature electrical detection of the spin polarization on the surface of Bi2Se3 by employing spin sensitive ferromagnetic tunnel contacts. The current-induced spin polarization on the Bi2Se3 surface is probed by measuring the magnetoresistance while switching the magnetization direction of the ferromagnetic detector. A spin resistance of up to 70 mΩ is measured at room temperature, which increases linearly with current bias, reverses sign with current direction, and decreases with higher TI thickness. The magnitude of the spin signal, its sign, and control experiments, using different measurement geometries and interface conditions, rule out other known physical effects. These findings provide further information about the electrical detection of current-induced spin polarizations in 3D TIs at ambient temperatures and could lead to innovative spin-based technologies.
Collapse
Affiliation(s)
- André Dankert
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE 41296 Göteborg, Sweden
| | - Johannes Geurs
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE 41296 Göteborg, Sweden
| | - M Venkata Kamalakar
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE 41296 Göteborg, Sweden
| | - Sophie Charpentier
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE 41296 Göteborg, Sweden
| | - Saroj P Dash
- Department of Microtechnology and Nanoscience, Chalmers University of Technology , SE 41296 Göteborg, Sweden
| |
Collapse
|
31
|
Zhao B, Chen T, Pan H, Fei F, Han Y. Electronic interference transport and its electron-phonon interaction in the Sb-doped Bi2Se3 nanoplates synthesized by a solvothermal method. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:465302. [PMID: 26523916 DOI: 10.1088/0953-8984/27/46/465302] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Here we synthesized the antimony doped [Formula: see text] nanoplates by the solvothermal method. The angle-dependent magnetoconductance study was carried out and all the [Formula: see text] were found to be normalized to the perpendicular field, indicating a clear 2D electronic state. The features of weak antilocalization and universal conductance fluctuations were clearly identified in the magnetoresistance transport of the 4-probe nanodevices. The dephasing lengths are extracted respectively according to the Hikami-Larkin-Nagaoka theory. It is attributed to the involvement of the dynamic spin centers. The dephasing lengths are found to increase with the decreasing temperature following a [Formula: see text] law with [Formula: see text]. This reveals the additional dephasing source of electron-phonon interaction, which is often absent for pure 2D electronic systems.
Collapse
Affiliation(s)
- Bo Zhao
- National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, and College of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | | | | | | | | |
Collapse
|
32
|
Wu L, Tse WK, Brahlek M, Morris CM, Aguilar RV, Koirala N, Oh S, Armitage NP. High-Resolution Faraday Rotation and Electron-Phonon Coupling in Surface States of the Bulk-Insulating Topological Insulator Cu_{0.02}Bi_{2}Se_{3}. PHYSICAL REVIEW LETTERS 2015; 115:217602. [PMID: 26636873 DOI: 10.1103/physrevlett.115.217602] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2015] [Indexed: 06/05/2023]
Abstract
We have utilized time-domain magnetoterahertz spectroscopy to investigate the low-frequency optical response of the topological insulator Cu_{0.02}Bi_{2}Se_{3} and Bi_{2}Se_{3} films. With both field and frequency dependence, such experiments give sufficient information to measure the mobility and carrier density of multiple conduction channels simultaneously. We observe sharp cyclotron resonances (CRs) in both materials. The small amount of Cu incorporated into the Cu_{0.02}Bi_{2}Se_{3} induces a true bulk insulator with only a single type of conduction with a total sheet carrier density of ~4.9×10^{12}/cm^{2} and mobility as high as 4000 cm^{2}/V·s. This is consistent with conduction from two virtually identical topological surface states (TSSs) on the top and bottom of the film with a chemical potential ~145 meV above the Dirac point and in the bulk gap. The CR broadens at high fields, an effect that we attribute to an electron-phonon interaction. This assignment is supported by an extended Drude model analysis of the zero-field Drude conductance. In contrast, in normal Bi_{2}Se_{3} films, two conduction channels were observed, and we developed a self-consistent analysis method to distinguish the dominant TSSs and coexisting trivial bulk or two-dimensional electron gas states. Our high-resolution Faraday rotation spectroscopy on Cu_{0.02}Bi_{2}Se_{3} paves the way for the observation of quantized Faraday rotation under experimentally achievable conditions to push the chemical potential in the lowest Landau level.
Collapse
Affiliation(s)
- Liang Wu
- The Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Wang-Kong Tse
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Department of Physics and Astronomy, MINT Center, University of Alabama, Tuscaloosa, Alabama 35487, USA
| | - M Brahlek
- Department of Physics and Astronomy, Rutgers the State University of New Jersey, New Jersey, Piscataway 08854, USA
| | - C M Morris
- The Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - R Valdés Aguilar
- The Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - N Koirala
- Department of Physics and Astronomy, Rutgers the State University of New Jersey, New Jersey, Piscataway 08854, USA
| | - S Oh
- Department of Physics and Astronomy, Rutgers the State University of New Jersey, New Jersey, Piscataway 08854, USA
| | - N P Armitage
- The Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| |
Collapse
|
33
|
Song CL, Wang L, He K, Ji SH, Chen X, Ma XC, Xue QK. Probing Dirac fermion dynamics in topological insulator Bi2Se3 films with a scanning tunneling microscope. PHYSICAL REVIEW LETTERS 2015; 114:176602. [PMID: 25978246 DOI: 10.1103/physrevlett.114.176602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Indexed: 06/04/2023]
Abstract
Scanning tunneling microscopy and spectroscopy have been used to investigate the femtosecond dynamics of Dirac fermions in the topological insulator Bi2Se3 ultrathin films. At the two-dimensional limit, bulk electrons become quantized and the quantization can be controlled by the film thickness at a single quintuple layer level. By studying the spatial decay of standing waves (quasiparticle interference patterns) off steps, we measure directly the energy and film thickness dependence of the phase relaxation length lϕ and inelastic scattering lifetime τ of topological surface-state electrons. We find that τ exhibits a remarkable (E - EF)(-2) energy dependence and increases with film thickness. We show that the features revealed are typical for electron-electron scattering between surface and bulk states.
Collapse
Affiliation(s)
- Can-Li Song
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Lili Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Ke He
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Shuai-Hua Ji
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Xi Chen
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Xu-Cun Ma
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| |
Collapse
|
34
|
Tang H, Wang X, Xiong Y, Zhao Y, Zhang Y, Zhang Y, Yang J, Xu D. Thermoelectric characterization of individual bismuth selenide topological insulator nanoribbons. NANOSCALE 2015; 7:6683-90. [PMID: 25798738 DOI: 10.1039/c5nr00917k] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Bismuth selenide (Bi2Se3) nanoribbons have attracted tremendous research interest recently to study the properties of topologically protected surface states that enable new opportunities to enhance the thermoelectric performance. However, the thermoelectric characterization of individual Bi2Se3 nanoribbons is rare due to the technological challenges in the measurements. One challenge is to ensure good contacts between the nanoribbon and electrodes in order to determine the thermal and electrical properties accurately. In this work, we report the thermoelectric characterization of individual Bi2Se3 nanoribbons via a suspended microdevice method. Through careful measurements, we have demonstrated that contact thermal resistance is negligible after the electron-beam-induced deposition (EBID) of platinum/carbon (Pt/C) composites at the contacts between the nanoribbon and electrodes. It is shown that the thermal conductivity of the Bi2Se3 nanoribbons is less than 50% of the bulk value over the whole measurement temperature range, which can be attributed to enhanced phonon boundary scattering. Our results indicate that intrinsic Bi2Se3 nanoribbons prepared in this work are highly doped n-type semiconductors, and therefore the Fermi level should be in the conduction band and no topological transport behavior can be observed in the intrinsic system.
Collapse
Affiliation(s)
- Hao Tang
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong Special Administrative Region.
| | | | | | | | | | | | | | | |
Collapse
|
35
|
Glinka YD, Babakiray S, Johnson TA, Lederman D. Thickness tunable quantum interference between surface phonon and Dirac plasmon states in thin films of the topological insulator Bi₂Se₃. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:052203. [PMID: 25614684 DOI: 10.1088/0953-8984/27/5/052203] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report on a >100-fold enhancement of Raman responses from Bi2Se3 thin films if laser photon energy switches from 2.33 eV (532 nm) to 1.58 eV (785 nm), which is due to direct optical coupling to Dirac surface states (SS) at the resonance energy of ∼1.5 eV (a thickness-independent enhancement) and due to nonlinearly excited Dirac plasmon (a thickness-dependent enhancement). Owing to the direct optical coupling, we observed an in-plane phonon mode of hexagonally arranged Se-atoms associated with a continuous network of Dirac SS. This mode revealed a Fano lineshape for films <15 nm thick, resulting from quantum interference between surface phonon and Dirac plasmon states.
Collapse
Affiliation(s)
- Yuri D Glinka
- Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506-6315, USA. Institute of Physics, National Academy of Sciences of Ukraine, Kiev 03028, Ukraine
| | | | | | | |
Collapse
|
36
|
Rosenstein B, Shapiro BY, Li D, Shapiro I. Triplet superconductivity in 3D Dirac semi-metal due to exchange interaction. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:025701. [PMID: 25501668 DOI: 10.1088/0953-8984/27/2/025701] [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
Conventional phonon-electron interaction induces either triplet or one of two (degenerate) singlet pairing states in time reversal and inversion invariant 3D Dirac semi-metal. Investigation of the order parameters and energies of these states at zero temperature in a wide range of values of chemical potential μ, the effective electron-electron coupling constant λ and Debye energy TD demonstrates that when the exchange interaction is neglected the singlet always prevails, however, in significant portions of the (μ, λ, TD) parameter space the energy difference is very small. This means that interactions that are small, but discriminate between the spin singlet and the spin triplet, are important in order to determine the nature of the superconducting order there. The best candidate for such an interaction in the materials under consideration is the exchange (the Stoner term) characterized by constant λex. We show that at values of λex, much smaller than ones creating Stoner instability to ferromagnetism λex ∼ 1, the triplet pairing becomes energetically favored over the singlet ones. The 3D quantum critical point at μ = 0 is considered in detail. This can be realized experimentally in optically trapped cold atom systems.
Collapse
Affiliation(s)
- Baruch Rosenstein
- Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan, People's Republic of China. Applied Physics Department, Ariel University Center of Samaria, Ariel 40700, Israel
| | | | | | | |
Collapse
|
37
|
Sobota JA, Yang SL, Leuenberger D, Kemper AF, Analytis JG, Fisher IR, Kirchmann PS, Devereaux TP, Shen ZX. Distinguishing bulk and surface electron-phonon coupling in the topological insulator Bi(2)Se(3) using time-resolved photoemission spectroscopy. PHYSICAL REVIEW LETTERS 2014; 113:157401. [PMID: 25375740 DOI: 10.1103/physrevlett.113.157401] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Indexed: 06/04/2023]
Abstract
We report time- and angle-resolved photoemission spectroscopy measurements on the topological insulator Bi(2)Se(3). We observe oscillatory modulations of the electronic structure of both the bulk and surface states at a frequency of 2.23 THz due to coherent excitation of an A(1g) phonon mode. A distinct, additional frequency of 2.05 THz is observed in the surface state only. The lower phonon frequency at the surface is attributed to the termination of the crystal and thus reduction of interlayer van der Waals forces, which serve as restorative forces for out-of-plane lattice distortions. Density functional theory calculations quantitatively reproduce the magnitude of the surface phonon softening. These results represent the first band-resolved evidence of the A(1g) phonon mode coupling to the surface state in a topological insulator.
Collapse
Affiliation(s)
- J A Sobota
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA and Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - S-L Yang
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA and Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Department of Physics, Stanford University, Stanford, California 94305, USA
| | - D Leuenberger
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA and Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - A F Kemper
- Computational Research Division, Lawrence Berkeley National Lab, 1 Cyclotron Road, Berkeley, California 94720, USA
| | - J G Analytis
- Department of Physics, University of California, Berkeley, California 94720, USA
| | - I R Fisher
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA and Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - P S Kirchmann
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - T P Devereaux
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA and Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Z-X Shen
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA and Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Department of Physics, Stanford University, Stanford, California 94305, USA
| |
Collapse
|
38
|
Yilmaz T, Pletikosić I, Weber AP, Sadowski JT, Gu GD, Caruso AN, Sinkovic B, Valla T. Absence of a proximity effect for a thin-films of a Bi2Se3 topological insulator grown on top of a Bi2Sr2CaCu2O(8+δ) cuprate superconductor. PHYSICAL REVIEW LETTERS 2014; 113:067003. [PMID: 25148345 DOI: 10.1103/physrevlett.113.067003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Indexed: 06/03/2023]
Abstract
Proximity-induced superconductivity in a 3D topological insulator represents a new avenue for observing zero-energy Majorana fermions inside vortex cores. Relatively small gaps and low transition temperatures of conventional s-wave superconductors put hard constraints on these experiments. Significantly larger gaps and higher transition temperatures in cuprate superconductors might be an attractive alternative to considerably relax these constraints, but it is not clear whether the proximity effect would be effective in heterostructures involving cuprates and topological insulators. Here, we present angle-resolved photoemission studies of thin Bi(2)Se(3) films grown in situ on optimally doped Bi(2)Sr(2)CaCu(2)O(8+δ) substrates that show the absence of proximity-induced gaps on the surfaces of Bi(2)Se(3) films as thin as a 1.5 quintuple layer. These results suggest that the superconducting proximity effect between a cuprate superconductor and a topological insulator is strongly suppressed, likely due to a very short coherence length along the c axis, incompatible crystal and pairing symmetries at the interface, small size of the topological surface state's Fermi surface, and adverse effects of a strong spin-orbit coupling in the topological material.
Collapse
Affiliation(s)
- T Yilmaz
- Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA
| | - I Pletikosić
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA and Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - A P Weber
- National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - J T Sadowski
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - G D Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - A N Caruso
- Department of Physics, University of Missouri-Kansas City, Kansas City, Missouri 64110, USA
| | - B Sinkovic
- Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA
| | - T Valla
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| |
Collapse
|
39
|
Anomalous photoelectric effect of a polycrystalline topological insulator film. Sci Rep 2014; 4:5876. [PMID: 25069391 PMCID: PMC5376173 DOI: 10.1038/srep05876] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 07/11/2014] [Indexed: 11/28/2022] Open
Abstract
A topological insulator represents a new state of quantum matter that possesses an insulating bulk band gap as well as a spin-momentum-locked Dirac cone on the surface that is protected by time-reversal symmetry. Photon-dressed surface states and light-induced surface photocurrents have been observed in topological insulators. Here, we report experimental observations of an anomalous photoelectric effect in thin films of Bi2Te3, a polycrystalline topological insulator. Under illumination with non-polarised light, transport measurements reveal that the resistance of the topological surface states suddenly increases when the polycrystalline film is illuminated. The resistance variation is positively dependent on the light intensity but has no relation to the applied electric field; this finding can be attributed to the gap opening of the surface Dirac cone. This observation of an anomalous photoelectric effect in polycrystalline topological insulators offers exciting opportunities for the creation of photodetectors with an unusually broad spectral range. Moreover, polycrystalline topological insulator films provide an attractive material platform for exploring the nature and practical application of topological insulators.
Collapse
|
40
|
Barreto L, Kühnemund L, Edler F, Tegenkamp C, Mi J, Bremholm M, Iversen BB, Frydendahl C, Bianchi M, Hofmann P. Surface-dominated transport on a bulk topological insulator. NANO LETTERS 2014; 14:3755-3760. [PMID: 24940641 DOI: 10.1021/nl501489m] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Topological insulators are guaranteed to support metallic surface states on an insulating bulk, and one should thus expect that the electronic transport in these materials is dominated by the surfaces states. Alas, due to the high remaining bulk conductivity, it is challenging to achieve surface-dominated transport. Here we use nanoscale four-point setups with a variable contact distance on an atomically clean surface of bulk-insulating Bi2Te2Se. We show that the transport at 30 K is two-dimensional rather than three-dimensional, that is, surface-dominated, and we find a surface state mobility of 390(30) cm(2) V(-1) s(-1) at 30 K at a carrier concentration of 8.71(7) × 10(12) cm(-2).
Collapse
Affiliation(s)
- Lucas Barreto
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center (iNANO), Aarhus University , 8000 Aarhus C, Denmark
| | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Gibson QD, Evtushinsky D, Yaresko AN, Zabolotnyy VB, Ali MN, Fuccillo MK, Van den Brink J, Büchner B, Cava RJ, Borisenko SV. Quasi one dimensional Dirac electrons on the surface of Ru₂Sn₃. Sci Rep 2014; 4:5168. [PMID: 24893841 PMCID: PMC4044652 DOI: 10.1038/srep05168] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 05/14/2014] [Indexed: 11/09/2022] Open
Abstract
We present an ARPES study of the surface states of Ru2Sn3, a new type of a strong 3D topological insulator (TI). In contrast to currently known 3D TIs, which display two-dimensional Dirac cones with linear isotropic dispersions crossing through one point in the surface Brillouin Zone (SBZ), the surface states on Ru2Sn3 are highly anisotropic, displaying an almost flat dispersion along certain high-symmetry directions. This results in quasi-one dimensional (1D) Dirac electronic states throughout the SBZ that we argue are inherited from features in the bulk electronic structure of Ru2Sn3 where the bulk conduction bands are highly anisotropic. Unlike previous experimentally characterized TIs, the topological surface states of Ru2Sn3 are the result of a d-p band inversion rather than an s-p band inversion. The observed surface states are the topological equivalent to a single 2D Dirac cone at the surface Brillouin zone.
Collapse
Affiliation(s)
- Q. D. Gibson
- Department of Chemistry, Princeton University, Princeton, New Jersey, 08544, USA
| | - D. Evtushinsky
- Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany
| | - A. N. Yaresko
- Max-Planck-Institut für Festkörperforschung Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - V. B. Zabolotnyy
- Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany
| | - Mazhar N. Ali
- Department of Chemistry, Princeton University, Princeton, New Jersey, 08544, USA
| | - M. K. Fuccillo
- Department of Chemistry, Princeton University, Princeton, New Jersey, 08544, USA
| | - J. Van den Brink
- Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany
| | - B. Büchner
- Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany
- Institute for Solid State Physics, Technical University Dresden, D-01171 Dresden, Germany
| | - R. J. Cava
- Department of Chemistry, Princeton University, Princeton, New Jersey, 08544, USA
| | - S. V. Borisenko
- Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01069 Dresden, Germany
| |
Collapse
|
42
|
Li CH, van 't Erve OMJ, Robinson JT, Liu Y, Li L, Jonker BT. Electrical detection of charge-current-induced spin polarization due to spin-momentum locking in Bi2Se3. NATURE NANOTECHNOLOGY 2014; 9:218-224. [PMID: 24561354 DOI: 10.1038/nnano.2014.16] [Citation(s) in RCA: 132] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 01/17/2014] [Indexed: 06/03/2023]
Abstract
Topological insulators exhibit metallic surface states populated by massless Dirac fermions with spin-momentum locking, where the carrier spin lies in-plane, locked at right angles to the carrier momentum. Here, we show that a charge current produces a net spin polarization via spin-momentum locking in Bi2Se3 films, and this polarization is directly manifested as a voltage on a ferromagnetic contact. This voltage is proportional to the projection of the spin polarization onto the contact magnetization, is determined by the direction and magnitude of the charge current, scales inversely with Bi2Se3 film thickness, and its sign is that expected from spin-momentum locking rather than Rashba effects. Similar data are obtained for two different ferromagnetic contacts, demonstrating that these behaviours are independent of the details of the ferromagnetic contact. These results demonstrate direct electrical access to the topological insulators' surface-state spin system and enable utilization of its remarkable properties for future technological applications.
Collapse
Affiliation(s)
- C H Li
- Materials Science and Technology Division, Naval Research Laboratory, Washington, District of Columbia 20375, USA
| | - O M J van 't Erve
- Materials Science and Technology Division, Naval Research Laboratory, Washington, District of Columbia 20375, USA
| | - J T Robinson
- Electronics Science and Technology Division, Naval Research Laboratory, Washington, District of Columbia 20375, USA
| | - Y Liu
- Department of Physics, University of Wisconsin, Milwaukee, Wisconsin 53211, USA
| | - L Li
- Department of Physics, University of Wisconsin, Milwaukee, Wisconsin 53211, USA
| | - B T Jonker
- Materials Science and Technology Division, Naval Research Laboratory, Washington, District of Columbia 20375, USA
| |
Collapse
|
43
|
Chen C, Xie Z, Feng Y, Yi H, Liang A, He S, Mou D, He J, Peng Y, Liu X, Liu Y, Zhao L, Liu G, Dong X, Zhang J, Yu L, Wang X, Peng Q, Wang Z, Zhang S, Yang F, Chen C, Xu Z, Zhou XJ. Tunable Dirac fermion dynamics in topological insulators. Sci Rep 2014; 3:2411. [PMID: 23934507 PMCID: PMC3740283 DOI: 10.1038/srep02411] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 07/23/2013] [Indexed: 11/16/2022] Open
Abstract
Three-dimensional topological insulators are characterized by insulating bulk state and metallic surface state involving relativistic Dirac fermions which are responsible for exotic quantum phenomena and potential applications in spintronics and quantum computations. It is essential to understand how the Dirac fermions interact with other electrons, phonons and disorders. Here we report super-high resolution angle-resolved photoemission studies on the Dirac fermion dynamics in the prototypical Bi2(Te,Se)3 topological insulators. We have directly revealed signatures of the electron-phonon coupling and found that the electron-disorder interaction dominates the scattering process. The Dirac fermion dynamics in Bi2(Te3−xSex) topological insulators can be tuned by varying the composition, x, or by controlling the charge carriers. Our findings provide crucial information in understanding and engineering the electron dynamics of the Dirac fermions for fundamental studies and potential applications.
Collapse
Affiliation(s)
- Chaoyu Chen
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Luo CW, Wang HJ, Ku SA, Chen HJ, Yeh TT, Lin JY, Wu KH, Juang JY, Young BL, Kobayashi T, Cheng CM, Chen CH, Tsuei KD, Sankar R, Chou FC, Kokh KA, Tereshchenko OE, Chulkov EV, Andreev YM, Gu GD. Snapshots of Dirac fermions near the Dirac point in topological insulators. NANO LETTERS 2013; 13:5797-5802. [PMID: 24228733 DOI: 10.1021/nl4021842] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The recent focus on topological insulators is due to the scientific interest in the new state of quantum matter as well as the technology potential for a new generation of THz optoelectronics, spintronics and quantum computations. It is important to elucidate the dynamics of the Dirac fermions in the topologically protected surface state. Hence we utilized a novel ultrafast optical pump mid-infrared probe to explore the dynamics of Dirac fermions near the Dirac point. The femtosecond snapshots of the relaxation process were revealed by the ultrafast optics. Specifically, the Dirac fermion-phonon coupling strength in the Dirac cone was found to increase from 0.08 to 0.19 while Dirac fermions were away from the Dirac point into higher energy states. Further, the energy-resolved transient reflectivity spectra disclosed the energy loss rate of Dirac fermions at room temperature was about 1 meV/ps. These results are crucial to the design of Dirac fermion devices.
Collapse
Affiliation(s)
- C W Luo
- Department of Electrophysics and ‡Institute of Physics, National Chiao Tung University , Hsinchu, Taiwan
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
45
|
Di Pietro P, Ortolani M, Limaj O, Di Gaspare A, Giliberti V, Giorgianni F, Brahlek M, Bansal N, Koirala N, Oh S, Calvani P, Lupi S. Observation of Dirac plasmons in a topological insulator. NATURE NANOTECHNOLOGY 2013; 8:556-60. [PMID: 23872838 DOI: 10.1038/nnano.2013.134] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 06/12/2013] [Indexed: 05/26/2023]
Abstract
Plasmons are quantized collective oscillations of electrons and have been observed in metals and doped semiconductors. The plasmons of ordinary, massive electrons have been the basic ingredients of research in plasmonics and in optical metamaterials for a long time. However, plasmons of massless Dirac electrons have only recently been observed in graphene, a purely two-dimensional electron system. Their properties are promising for novel tunable plasmonic metamaterials in the terahertz and mid-infrared frequency range. Dirac fermions also occur in the two-dimensional electron gas that forms at the surface of topological insulators as a result of the strong spin-orbit interaction existing in the insulating bulk phase. One may therefore look for their collective excitations using infrared spectroscopy. Here we report the first experimental evidence of plasmonic excitations in a topological insulator (Bi2Se3). The material was prepared in thin micro-ribbon arrays of different widths W and periods 2W to select suitable values of the plasmon wavevector k. The linewidth of the plasmon was found to remain nearly constant at temperatures between 6 K and 300 K, as expected when exciting topological carriers. Moreover, by changing W and measuring the plasmon frequency in the terahertz range versus k we show, without using any fitting parameter, that the dispersion curve agrees quantitatively with that predicted for Dirac plasmons.
Collapse
Affiliation(s)
- P Di Pietro
- CNR-SPIN, Corso F. Perrone, 16152 Genoa, Italy
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
46
|
Kondo T, Nakashima Y, Ota Y, Ishida Y, Malaeb W, Okazaki K, Shin S, Kriener M, Sasaki S, Segawa K, Ando Y. Anomalous dressing of Dirac fermions in the topological surface state of Bi2Se3, Bi2Te3, and Cu-doped Bi2Se3. PHYSICAL REVIEW LETTERS 2013; 110:217601. [PMID: 23745936 DOI: 10.1103/physrevlett.110.217601] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Indexed: 06/02/2023]
Abstract
Quasiparticle dynamics on the topological surface state of Bi(2(3), Bi(2)Te(3), and superconducting Cu(x)Bi(2)Se(3) are studied by 7 eV laser-based angle resolved photoemission spectroscopy. We find strong mode couplings in the Dirac-cone surface states at energies of ~3 and ~15-20 meV associated with an exceptionally large coupling constant λ of ~3, which is one of the strongest ever reported for any material. This result is compatible with the recent observation of a strong Kohn anomaly in the surface phonon dispersion of Bi(2)Se(3), but it appears that the theoretically proposed "spin-plasmon" excitations realized in helical metals are also playing an important role. Intriguingly, the ~3 meV mode coupling is found to be enhanced in the superconducting state of Cu(x)Bi(2)Se(3).
Collapse
Affiliation(s)
- Takeshi Kondo
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
47
|
Garate I. Phonon-induced topological transitions and crossovers in Dirac materials. PHYSICAL REVIEW LETTERS 2013; 110:046402. [PMID: 25166179 DOI: 10.1103/physrevlett.110.046402] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Indexed: 06/03/2023]
Abstract
We show that electron-phonon interactions can alter the topological properties of Dirac insulators and semimetals, at both zero and nonzero temperature. Contrary to the common belief that increasing temperature always destabilizes topological phases, our results highlight instances in which phonons may lead to the appearance of topological surface states above a crossover temperature in a material that has a topologically trivial ground state.
Collapse
Affiliation(s)
- Ion Garate
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
| |
Collapse
|
48
|
Lysogorskiy YV, Kijamov AG, Nedopekin OV, Tayurskii DA. Ab initio studying of topological insulator Bi2Se3under the stress. ACTA ACUST UNITED AC 2012. [DOI: 10.1088/1742-6596/394/1/012022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
49
|
Kim D, Li Q, Syers P, Butch NP, Paglione J, Das Sarma S, Fuhrer MS. Intrinsic electron-phonon resistivity of Bi2Se3 in the topological regime. PHYSICAL REVIEW LETTERS 2012; 109:166801. [PMID: 23215109 DOI: 10.1103/physrevlett.109.166801] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Indexed: 06/01/2023]
Abstract
We measure the temperature-dependent carrier density and resistivity of the topological surface state of thin exfoliated Bi(2)Se(3) in the absence of bulk conduction. When the gate-tuned chemical potential is near or below the Dirac point, the carrier density is strongly temperature-dependent, reflecting thermal activation from the nearby bulk valence band, while, above the Dirac point, unipolar n-type surface conduction is observed with negligible thermal activation of bulk carriers. In this regime, linear resistivity vs temperature reflects intrinsic electron-acoustic phonon scattering. A quantitative comparison with a theoretical transport calculation including both phonon and disorder effects gives the ratio of deformation potential to Fermi velocity D/ħν(F)=4.7 Å(-1). This strong phonon scattering in the Bi(2)Se(3) surface state gives intrinsic limits for the conductivity and charge carrier mobility at room temperature of ~550 μS per surface and ~10,000 cm(2)/V s.
Collapse
Affiliation(s)
- Dohun Kim
- Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
| | | | | | | | | | | | | |
Collapse
|