Topological nature and the multiple Dirac cones hidden in Bismuth high-Tc superconductors

Gang Li; Binghai Yan; Ronny Thomale; Werner Hanke

doi:10.1038/srep10435

paper

Topological nature and the multiple Dirac cones hidden in Bismuth high-Tc superconductors

arXiv:1410.0821 · doi:10.1038/srep10435

Abstract

Recent theoretical studies employing density-functional theory have predicted BaBiO $_{3}$ (when doped with electrons) and YBiO $_{3}$ 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 $_{x}$ BiO $_{3}$ and BaPb $_{1 - x}$ Bi $_{x}$ O $_{3}$ , which are "high-Tc" bulk superconducting near 30 K, additionally display in the further vicinity of their Fermi energy $E_{F}$ 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 $E_{F}$ . 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 $E_{F}$ for further hole doping, which manifests these systems to be candidates for both electron- and hole-doped topological insulators.

8 pages, 5 figures, 1 table. Published version, open access

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Superconducting proximity effect and Majorana fermions at the surface of a topological insulator

Topological nature and the multiple Dirac cones hidden in Bismuth high-Tc superconductors

Abstract

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