Fan Yang,1* Subhamoy Ghatak,1 A. A. Taskin,1 Yoichi Ando,1 Yuichiro Ando,2 Masashi Shiraishi,2 Kouji Segawa,3 Yasushi Kanai,3 Kazuhiko Matsumoto,3 Achim Rosch4
1Institute of Physics II, University of Cologne, Zuelpicher Strasse 77, 50937 Koeln, Germany
2Department of Electronic Science and Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
3Institute of Scientiﬁc and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
4Institute of Theoretical Physics, University of Cologne, Zuelpicher Strasse 77, 50937 Koeln, Germany
Nano-Micro Conference, 2017, 1, 01069
Published Online: 31 October 2017 (Abstract)
The surface states of 3D topological insulators (TIs) possess a helical spin texture in which the spin and momentum are perpendicularly locked to each other. Due to this spin-momentum locking, a net spin polarization can be induced by a charge current and vice versa. However, topological surface states are expected to give rise to only one type of spin polarization for a given current direction, which has been a limiting factor for spin manipulations. In this talk we report that in devices based on the bulk-insulating topological insulator BiSbTeSe2, two different kinds of spin polarizations were observed in different devices: The spin polarization expected from the topological surface states was detected in a heavily electron-doped device, whereas the opposite polarization was reproducibly observed in devices with low carrier densities . We propose that the latter type of spin polarization stems from topologically-trivial two-dimensional states with a large Rashba spin splitting, which are caused by a strong band bending at the surface of BiSbTeSe2 beneath the ferromagnetic electrode used as a spin detector. This finding paves the way for realizing the “spin transistor” operation in future topological spintronic devices.
 F. Yang; S. Ghatak; A. A. Taskin; K. Segawa; Y. Ando; M. Shiraishi; Y. Kanai; K. Matsumoto; A. Rosch; Y. Ando, Switching of charge-current-induced spin polarization in the topological insulator BiSbTeSe2. Physical Review B. 94, 075304 (2016). doi:10.1103/PhysRevB.94.075304
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