[seminar] 25.11.2016. 11h Fan Yang: Observation of different types of charge-current-induced spin polarization in BiSbTeSe$_2$ topological insulators

[Damir Pajic]

Drage kolegice i kolege / Dear colleagues,

Drago mi je da mogu najaviti sljedeć‡i seminar / I would like to invite 
you to the following seminar :

petak/Friday 25. 11. 2016., 11:15 h predavaonica/room F201, II.kat

Observation of different types of charge-current-induced spin 
polarization in BiSbTeSe$_2$ topological insulators

Dr. Fan Yang

Institute of Physics II, University of Cologne, Koeln, Germany

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 BiSbTeSe$_2$, 
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 BiSbTeSe$_2$ 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.

Cjeloviti oglas je u prilogu./Formatted announcement is attached.

Lijep pozdrav / Best regards
Damir Pajić

-- 
_________________________________________________________
doc.dr.sc. Damir Pajic              Department of Physics
Assistant professor                    Faculty of Science
http://www.phy.pmf.unizg.hr/~dpajic  University of Zagreb

         Bijenička c. 32, HR-10000 Zagreb, Hrvatska(Croatia)

tel +385 1 4605538 mob +385 95 8136706 fax +385 1 4680336
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