Tunable inverse topological heterostructure utilizing (Bi_1−xIn_x)₂Se₃ and multichannel weak-antilocalization effect

In typical topological insulator (TI) systems the TI is bordered by a non-TI insulator, and the surrounding conventional insulators, including vacuum, are not generally treated as part of the TI system. Here, we implement a material system where the roles are reversed, and the topological surface states form around the non-TI (instead of the TI) layers. This is realized by growing a layer of the tunable non-TI (Bi1-xInx)2Se3 in between two layers of the TI Bi2Se3 using the atomically precise molecular beam epitaxy technique. On this tunable inverse topological platform, we systematically vary the thickness and the composition of the (Bi1-xInx)2Se3 layer and show that this tunes the coupling between the TI layers from strongly coupled metallic to weakly coupled, and finally to a fully decoupled insulating regime. This system can be used to probe the fundamental nature of coupling in TI materials and provides a tunable insulating layer for TI devices.