Candidates for topological insulators: Pb-based chalcogenide series

We theoretically predict that the series of Pb-based layered chalcogenides, Pb(n)Bi(2)Se(n+3) and Pb(n)Sb(2)Te(n+3), are possible new candidates for topological insulators, and the topological phases are changed from a topological insulator to a band insulator with increasing n. Among the new topological insulators, we found a large bulk band gap of 0.40 eV in PbBi(2)Se(4), and that of Pb(2)Sb(2)Te(5) is located near the phase boundary between a trivial and a nontrivial topological insulator, which raises the possibility of tuning the topological phase by changing the external parameters.