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Title: Ultrafast Spin-to-Charge Conversion at the Surface of Topological Insulator Thin Films

Strong spin–orbit coupling, resulting in the formation of spin–momentum–locked surface states, endows topological insulators with superior spin–to–charge conversion characteristics, though the dynamics that govern it have remained elusive. Here, an all–optical method is presented, which enables unprecedented tracking of the ultrafast dynamics of spin–to–charge conversion in a prototypical topological insulator Bi 2Se 3/ferromagnetic Co heterostructure, down to the sub–picosecond timescale. Compared to pure Bi 2Se 3 or Co, a giant terahertz emission is observed in the heterostructure that originates from spin–to–charge conversion, in which the topological surface states play a crucial role. A 0.12 ps timescale is identified that sets a technological speed limit of spin–to–charge conversion processes in topological insulators. Additionally, it is shown that the spin–to–charge conversion efficiency is temperature independent in Bi 2Se 3 as expected from the nature of the surface states, paving the way for designing next–generation high–speed optospintronic devices based on topological insulators at room temperature.
Authors:
 [1] ;  [2] ;  [3] ;  [3] ;  [3] ;  [3] ;  [2] ;  [2] ;  [2] ; ORCiD logo [4] ;  [5] ;  [6] ;  [3] ;  [2]
  1. Nanyang Technological Univ. (Singapore); Chinese Academy of Sciences (CAS), Beijing (China)
  2. Nanyang Technological Univ. (Singapore)
  3. National Univ. of Singapore (Singapore)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  5. Nanyang Technological Univ. (Singapore); Vienna Univ. of Technology, Vienna (Austria)
  6. Nanyang Technological Univ. (Singapore); Institute of High Performance Computing (Singapore)
Publication Date:
Report Number(s):
LA-UR-18-21690
Journal ID: ISSN 0935-9648
Grant/Contract Number:
89233218CNA000001
Type:
Accepted Manuscript
Journal Name:
Advanced Materials
Additional Journal Information:
Journal Name: Advanced Materials; Journal ID: ISSN 0935-9648
Publisher:
Wiley
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Material Science; spin‐to‐charge conversion; spintronics; surface states; terahertz emission spectroscopy; topological insulators
OSTI Identifier:
1482931

Wang, Xinbo, Cheng, Liang, Zhu, Dapeng, Wu, Yang, Chen, Mengji, Wang, Yi, Zhao, Daming, Boothroyd, Chris B., Lam, Yeng Ming, Zhu, Jian -Xin, Battiato, Marco, Song, Justin C. W., Yang, Hyunsoo, and Chia, Elbert E. M.. Ultrafast Spin-to-Charge Conversion at the Surface of Topological Insulator Thin Films. United States: N. p., Web. doi:10.1002/adma.201802356.
Wang, Xinbo, Cheng, Liang, Zhu, Dapeng, Wu, Yang, Chen, Mengji, Wang, Yi, Zhao, Daming, Boothroyd, Chris B., Lam, Yeng Ming, Zhu, Jian -Xin, Battiato, Marco, Song, Justin C. W., Yang, Hyunsoo, & Chia, Elbert E. M.. Ultrafast Spin-to-Charge Conversion at the Surface of Topological Insulator Thin Films. United States. doi:10.1002/adma.201802356.
Wang, Xinbo, Cheng, Liang, Zhu, Dapeng, Wu, Yang, Chen, Mengji, Wang, Yi, Zhao, Daming, Boothroyd, Chris B., Lam, Yeng Ming, Zhu, Jian -Xin, Battiato, Marco, Song, Justin C. W., Yang, Hyunsoo, and Chia, Elbert E. M.. 2018. "Ultrafast Spin-to-Charge Conversion at the Surface of Topological Insulator Thin Films". United States. doi:10.1002/adma.201802356.
@article{osti_1482931,
title = {Ultrafast Spin-to-Charge Conversion at the Surface of Topological Insulator Thin Films},
author = {Wang, Xinbo and Cheng, Liang and Zhu, Dapeng and Wu, Yang and Chen, Mengji and Wang, Yi and Zhao, Daming and Boothroyd, Chris B. and Lam, Yeng Ming and Zhu, Jian -Xin and Battiato, Marco and Song, Justin C. W. and Yang, Hyunsoo and Chia, Elbert E. M.},
abstractNote = {Strong spin–orbit coupling, resulting in the formation of spin–momentum–locked surface states, endows topological insulators with superior spin–to–charge conversion characteristics, though the dynamics that govern it have remained elusive. Here, an all–optical method is presented, which enables unprecedented tracking of the ultrafast dynamics of spin–to–charge conversion in a prototypical topological insulator Bi2Se3/ferromagnetic Co heterostructure, down to the sub–picosecond timescale. Compared to pure Bi2Se3 or Co, a giant terahertz emission is observed in the heterostructure that originates from spin–to–charge conversion, in which the topological surface states play a crucial role. A 0.12 ps timescale is identified that sets a technological speed limit of spin–to–charge conversion processes in topological insulators. Additionally, it is shown that the spin–to–charge conversion efficiency is temperature independent in Bi2Se3 as expected from the nature of the surface states, paving the way for designing next–generation high–speed optospintronic devices based on topological insulators at room temperature.},
doi = {10.1002/adma.201802356},
journal = {Advanced Materials},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {10}
}

Works referenced in this record:

Colloquium: Topological insulators
journal, November 2010

Topological insulators in Bi2Se3, Bi2Te3 and Sb2Te3 with a single Dirac cone on the surface
journal, May 2009
  • Zhang, Haijun; Liu, Chao-Xing; Qi, Xiao-Liang
  • Nature Physics, Vol. 5, Issue 6, p. 438-442
  • DOI: 10.1038/nphys1270