title: New Class of 3D Topological Insulator in Double Perovskite.
abstract: We predict a new class of 3D topological insulators (TIs) in which the spin-orbit coupling (SOC) can more effectively generate band gap. Band gap of conventional TI is mainly limited by two factors, the strength of SOC and, from electronic structure perspective, the band gap when SOC is absent. While the former is an atomic property, the latter can be minimized in a generic rock-salt lattice model in which a stable crossing of bands at the Fermi level along with band character inversion occurs in the absence of SOC. Thus large-gap TIs or TIs composed of lighter elements can be expected. In fact, we find by performing first-principles calculations that the model applies to a class of double perovskites A2BiXO6(A = Ca, Sr, Ba; X = Br, I) and the band gap is predicted up to 0.55 eV. Besides, surface Dirac cones are robust against the presence of dangling bond at boundary.
authors.affiliation: Department of Physics and Astronomy, University of California , Irvine, California 92697-4575, United States.
authors.forename: Shu-Ting
authors.identifier: http://orcid.org/0000-0003-2737-3969
authors.initials: ST
authors.lastname: Pi
authors.affiliation: Department of Physics and Astronomy, University of California , Irvine, California 92697-4575, United States.
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Physics and Astronomy, University of California , Irvine, California 92697-4575, United States.
authors.forename: Jeongwoo
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Physics and Astronomy, University of California , Irvine, California 92697-4575, United States.
authors.forename: Ruqian
authors.initials: R
authors.lastname: Wu
authors.affiliation: Center of General Education, National Taiwan Normal University , Taipei 116, Taiwan.
authors.forename: Yin-Kuo
authors.initials: YK
authors.lastname: Wang
authors.affiliation: Department of Physics, National Taiwan Normal University , Taipei 11677, Taiwan.
authors.forename: Chi-Ken
authors.identifier: http://orcid.org/0000-0003-1329-6069
authors.initials: CK
authors.lastname: Lu