Strain Effects in Topological Insulators: Topological Order and the Emergence of Switchable Topological Interface States in Sb$_2$Te$_3$/Bi$_2$Te$_3$ Heterojunctions

摘要

Strain can induce a topological phase transition in bismuth dichalcogenides.We present the phase diagram for 3D topological insulators Bi$_2$Te$_3$,Sb$_2$Te$_3$, Bi$_2$Se$_3$ and Sb$_2$Se$_3$ with uniaxial and biaxal strain,which show metallic and insulating phases, both topologically trivial andnon-trivial. In particular, uniaxial tension can drive Sb$_2$Te$_3$ into atopologically trivial insulating phase. Thus, we propose aSb$_2$Te$_3$/Bi$_2$Te$_3$ heterojunction in which a topological interface statearises in the common gap of this topological insulator-normal insulatorheterojunction that can be switched on or off by means of uniaxial strain. Thisinterface state is confined in the Sb$_2$Te$_3$ subsystem and is physicallyprotected from ambient impurities. Therefore, Sb$_2$Te$_3$/Bi$_2$Te$_3$heterojunctions can host robust helical interface states with promisingspintronic applications.