title: Topological nature and the multiple Dirac cones hidden in Bismuth high-Tc superconductors.
abstract: Recent theoretical studies employing density-functional theory have predicted BaBiO3 (when doped with electrons) and YBiO3 to become a topological insulator (TI) with a large topological gap (~0.7 eV). This, together with the natural stability against surface oxidation, makes the Bismuth-Oxide family of special interest for possible applications in quantum information and spintronics. The central question, we study here, is whether the hole-doped Bismuth Oxides, i.e. Ba(1-x)K(x)BiO3 and BaPb(1-x)Bi(x)O3, which are "high-Tc" bulk superconducting near 30 K, additionally display in the further vicinity of their Fermi energy EF a topological gap with a Dirac-type of topological surface state. Our electronic structure calculations predict the K-doped family to emerge as a TI, with a topological gap above EF. Thus, these compounds can become superconductors with hole-doping and potential TIs with additional electron doping. Furthermore, we predict the Bismuth-Oxide family to contain an additional Dirac cone below EF for further hole doping, which manifests these systems to be candidates for both electron- and hole-doped topological insulators.
authors.affiliation: Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany.
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.affiliation: 1] Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany [2] Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany.
authors.forename: Binghai
authors.initials: B
authors.lastname: Yan
authors.affiliation: Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany.
authors.forename: Ronny
authors.initials: R
authors.lastname: Thomale
authors.affiliation: Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Hanke