Bi2Se3/Bi2Se3 and TlSe/TlSe junctions: enhanced coupling of topological interface states by intercalation

Based on first-principles calculations, we studied the coupling of topological interface states at the interface of Bi2Se3/Bi2Se3 and TlSe/TlSe junctions. From our calculations, the coupling leads to an energy gap at the Dirac point of topological interface states and the energy gap is an exponential decay function of interface spacing when the interface spacing is large enough. The law of exponential decay may be used to identify the formation of interface states from interface-bulk mixed states. It also suggests that the coupling is caused by quantum tunneling. The coupling of the interface states in TlSe/TlSe can be greatly enhanced by intercalating hexagonal BN, although hexagonal BN is often used as a 2D substrate or insulator. The intercalation of bilayer BN or single atomic Au layer can further enhance the interfacial coupling. Our calculations may be helpful for the application of junctions composed of topological insulators.