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New Candidates for Topological Insulators : Pb-based chalcogenide series

In this talk, 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 0.40eV in PbBi 2 Se 4 and that Pb 2 Sb 2 Te 5 is located near the phase boundary between trivial and non-trivial topological insulator, which raises the possibility of tuning the topological phase by changing external parameters.