Switching of Charge-Current-Induced Spin Polarization in the Topological   Insulator BiSbTeSe2
  The charge-current-induced spin polarization is a key property of topological insulators for their applications in spintronics. 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. Here we report that in devices based on the bulk-insulating topological insulator BiSbTeSe2, an unexpected switching of spin polarization was observed upon changing the chemical potential. 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. 
Fan Yang, Subhamoy Ghatak, A. A. Taskin, Kouji Segawa, Yuichiro Ando,   Masashi Shiraishi, Yasushi Kanai, Kazuhiko Matsumoto...
cond-mat.mes-hall cond-mat.mtrl-sci