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4시 20분부터 제1과학관 31214 e+강의실에서 간단한 다과를 제공합니다.

아 래

Title: Manipulating spins in topological insulators

Speaker: 이  준  수  박사님 (California NanoSystems Institute, University of California)

Date & Time: Sep. 7(Wed.) 2016, 4:30 PM

Place: Natural Science 1,  Room No. 31214

Abstract: 

In three-dimensional topological insulators, a band inversion by a strong spin-orbit coupling induces metallic surface states in the bulk band gap. The inherently spin-polarized surface state is robust(“topologically protected”) against back scattering, which has attracted much attention from condensed matter physics and spintronics communities. Indeed, it has been experimentally demonstrated that topological insulators are promising materials for spintronics: a spin-transfer torque of record efficiency was reported[1], and spin pumping measurements suggest a spin Hall angle of a topological insulator is larger than in many currently studied materials [2]. Current issues in ‘topological spintronics” include electrical detection and manipulation of the spin-polarized topological surface state. In this talk, I will discuss recent studies of the direct electrical detection of the current-induced spin polarization in topological insulators. A control of spin signals by changing the current direction and by tuning the chemical potential will be demonstrated [3]. I will also discuss a different approach to manipulate the spin-textured surface state by breaking time-reversal symmetry in a topological insulator interfaced with a ferromagnetic semiconductor. The resulting magnetic gap at the Dirac point is evidenced as the chemical potential approaches the Dirac point or as temperature lowers. If time allows, I will briefly talk about another topic of my current studies: epi-superconductor/2D semiconductor hybrid systems towards topological superconductivity and quantum computing applications.

[1] A. Mellnik, J.S.LEE et al., Nature 511, 449 (2014)

[2] M. Jamali, J.S.LEE et al., Nano Lett., 15, 7126 (2015)

[3] J.S.Lee et al., Phys Rev B, 92, 155312 (2015)