Emergent <i>Z</i>₂ topological phases in (001) oxide superlattices

Complex oxides exhibit many exotic properties, including high-temperature superconductivity, colossal magnetoresistance, metal-insulator transition, etc. However, the intensively studied Z₂ topological insulating state has yet to be realized in complex oxides. In this work, we combine first-principle calculations and model analysis to show that, in a number of (001) (ABO₃)₁/(AB’O₃)₁ oxide superlattices, a proper band alignment can induce a parity inversion between B-d and B’-d states. Spin-orbit coupling opens a topologically nontrivial gap in the superlattice and results in a three-dimensional topological insulating state with Z₂ index 1(001). Our work shows that, while two bulk constituent oxides are topologically trivial, the superlattices they compose can have non-trivial topological properties -- a demonstration of emergent phenomena in oxide heterostructures.