Proximity Effects on Topological Surface States in Topological Insulators and Semimetals from First Principles
Topological insulators and topolgical semimetals have drawn a lot of attention due to topological invariants and resultant topologically protected surface states, as well as due to applications for spintronics and thermoelectrics. Various heterostructures involving topological materials have been built such as II-VI semiconductor ZnxCd1-xSe layers, Bi bilayers, graphene, boron nitride, and ferromagnetic insulators on top of topological insulator Bi2Se3, to name a few. In the heterostructures it is critical to understand how the topological surface states are influenced by various interfaces. The topological surface states can be coupled to bulk-like states or two-dimensional quantum-well states at the interface. Charge transfer may occur between the topological insulator and a non-topological substrate or overlayer at the interface. I will present effects of non-magnetic and magnetic interfaces on the characteristics of the surface-state Dirac cones in Bi2Se3, by using first-principles calculations, and compare with experiment. I will also discuss effects of asymmetric charge transfer on a thin Dirac semimetal film from first-principles calculations.