Weak topological insulators in PbTe/SnTe superlattices

It is desirable to realize topological phases in artificial structures by engineering electronic band structures. In this paper we investigate (PbTe)m(SnTe)2n_-m superlattices along the [001] direction and find a robust weak topological insulator phase for a large variety of layer numbers m and 2n-m. We confirm this topologically nontrivial phase by calculating Z₂ topological invariants and topological surface states based on the first-principles calculations. We show that the folding of Brillouin zone due to the superlattice structure plays an essential role in inducing topologically nontrivial phases in this system. This mechanism can be generalized to other systems in which band inversion occurs at multiple momenta, and gives us a brand new way to engineer topological materials in artificial structures.