Intrinsic Rashba-like splitting in asymmetric Bi₂Te ₃/Sb₂Te₃ heterogeneous topological insulator films

We show by density functional theory calculations that asymmetric hetero-stacking of Bi₂Te₃/Sb₂Te₃ films can modulate the topological surface states. Due to the structure inversion asymmetry, an intrinsic Rashba-like splitting of the conical surface bands is aroused. While such splitting in homogeneous Bi₂Te ₃-class topological insulators can be realized in films with more than three quintuple layers under external electric fields, the hetero-stacking breaks the limit of thickness for preserving the topological nature into the thinnest two quintuple layers. These results indicate that the hetero-stacking can serve as an efficient strategy for spin-resolved band engineering of topological insulators.