연사: 노한진교수(전남대학교 물리학과)
제목: Exploring Unique Properties of Topological Surface States by ARPES
초록:
Discovery of topological insulators (TIs) evokes renewed interest on unique physical properties of metallic surface/interface states at TI interfaces, which originates from topological invariants. Experimental efforts to confirm those properties of topological surface states (TSSs) in various environments lead to find unusual robustness of TSSs and formation of two dimensional electron gas (2DEG) states in Bi2X3 (X=Se, Te) (111) surfaces. In this talk, I will briefly introduce the basic concept of topological insulators and angle-resolved photoemission spectroscopy (ARPES), and present our two case studies for the unique properties of TSS’s. One is for the persistence of the TSS in Bi0.9Sb0.1[1], and the other is for controllability of the 2DEGs at a metal/Bi2Se3 interface[2]. In both studies, we evaporated pure magnetic/nonmagnetic metal atoms (Cu, Mn, In) on an in-situ cleaved TI surface and observed an evolution/devolution of the TSS’s by ARPES. The TSSs in Bi0.9Sb0.1 show unusual persistence against the surface impurities as is expected in a topological argument, and the TSSs in Bi2Se3 develop into 2DEG states as reported in literatures but they can be controlled by choosing an appropriate kind of metal elements and by applying a low temperature evaporation procedure.