“Spin-charge conversion in topological insulators for spintronic applications”

Dr. Joon Sue Lee
University of Tennessee, Incoming Assistant Professor in Physics

Sep. 27 (Fri.), 02:30 PM
E6-2. 1st fl. #1323

Abstract:
Surface states of topological insulators (TIs) are characterized by a helical spin texture in momentum space. The spin texture has been demonstrated by spin- and angle-resolve photoemission spectroscopy, and the current-induced spin polarization in the surface states has been detected by electrical transport measurements. The inherent “spin-momentum locking” makes TIs promising for spintronic device applications. In this talk, I will present experiments revealing highly efficient charge-to-spin and spin-to-charge conversion in TI/metallic-ferromagnetic (FM) bilayer systems: A charge current in a TI can be converted into a spin current that exerts spin-transfer torque into an FM; A spin current injected from an FM into a TI, by spin pumping method, can be converted into a charge signal (voltage); Current-direction dependent (unidirectional) magnetoresistance in TI/FM bilayer systems has been observed with a much lower current density in comparison to normal-metal/FM bilayer systems. Ideally, TI/insulating-FM bilayer systems have potential to achieve even higher efficiency in spin-charge conversion by restricting electrical conduction to a TI layer. I will discuss the role of the TI surface states in spin-to-charge conversion process and a consequence of breaking time-reversal symmetry using TI/insulating-FM systems.