Candidates for topological insulators: Pb-based chalcogenide series

We theoretically predict that the series of Pb-based layered chalcogenides, Pb_nBi₂Se_n+3and Pb_nSb ₂Te_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 PbBi₂Se₄, and that of Pb₂Sb₂Te₅ 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.