Engineering Topological Superlattices: Prospects and Limitations

We developed a new artificial topological insulator (TI) system in heterostructure films consisting of alternating Bi₂Se₃ (topological) and In₂Se₃ (trivial) layers grown via molecular beam epitaxy (MBE). Building upon our past work on similar superlattices, here we systematically explore both the prospects and limitations of this model. Due to weak interlayer bonding energies in these van der Waals systems, we find that this topological superlattice structure tends to develop non-ideal, wavy interfaces as the number of superlattices grows. However, despite such structural imperfections, we discover that some of the electronic transport properties such as the weak antilocalization (WAL) effect robustly represent the well-defined quantized values of superlattice unit cells. The particularly remarkable robustness of the WAL effect allows us to map out a phase diagram for this artificial topological material as a function of intra- and inter- coupling strengths between the topological and trivial unit layers.