title: Superconductivity in defective pyrite-type iridium chalcogenides Ir(x)Ch2 Ch = Se and Te.
abstract: We report superconductivity in defective pyrite-type iridium chalcogenides Ir(x)Ch2 (Ch = Se and Te). Maximum values of T(c) of 6.4 K for Ir(0.91)Se(2) and 4.7 K for Ir(0.93)Te(2) were observed. It was found that Ir(0.75)Ch(2) (Ir(3)Ch(8)) is close to the boundary between metallic and insulating states and Ir(x)Ch(2) systems undergo nonmetal to metal transitions as x increases. On the basis of density functional theory calculations and the observed large variation in the Ch-Ch distance with x, we suggest that Ir(0.75)Ch(2) (Ir(3)Ch(8)) is the parent compound for the present superconductors.
authors.affiliation: Frontier Research Center, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan.
authors.forename: Yanpeng
authors.initials: Y
authors.lastname: Qi
authors.forename: Satoru
authors.initials: S
authors.lastname: Matsuishi
authors.forename: Jiangang
authors.initials: J
authors.lastname: Guo
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Mizoguchi
authors.forename: Hideo
authors.initials: H
authors.lastname: Hosono