Induced Robust Topological Order on an Ordinary Insulator Heterostructured with a Strong Topological Insulator*

Three of V(Bi, Sb)-VI(Se, Te) binary compounds are predicted and confirmed to be strong topological insulators (STIs). The exception for Sb₂Se₃ to be an ordinary insulator (OI) is due to the weaker spin-orbit coupling. Here, we report that the rhombohedral phase of Sb₂Se₃ is successfully grown by molecular beam epitaxy on films of Bi₂Se₃ (an STI) and In₂Se₃ (an OI). Surface electronic structures of these heterostructures are investigated by angle-resolved photoemission spectroscopy. In the OI/STI heterostructure, a Dirac cone topological surface state (TSS) is found to be induced on the Sb₂Se₃ layer up to 15 nm thick, in sharp contrast with the OI/OI heterostructure where no sign of TSS can be observed.