title: Two-orbital model explains the higher transition temperature of the single-layer Hg-cuprate superconductor compared to that of the La-cuprate superconductor.
abstract: In order to explore the reason why the single-layered cuprates, La(2-x)(Sr/Ba)(x)CuO4 (T(c)≃40  K) and HgBa2CuO(4+δ) (T(c)≃90  K) have such a significant difference in T(c), we study a two-orbital model that incorporates the d(z2) orbital on top of the d(x2-y2) orbital. It is found, with the fluctuation exchange approximation, that the d(z2) orbital contribution to the Fermi surface, which is stronger in the La system, works against d-wave superconductivity, thereby dominating over the effect of the Fermi surface shape. The result resolves the long-standing contradiction between the theoretical results on Hubbard-type models and the experimental material dependence of T(c) in the cuprates.
authors.affiliation: Department of Applied Physics and Chemistry, The University of Electro-Communications, Chofu, Tokyo 182-8585, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Sakakibara
authors.forename: Hidetomo
authors.initials: H
authors.lastname: Usui
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Kuroki
authors.forename: Ryotaro
authors.initials: R
authors.lastname: Arita
authors.forename: Hideo
authors.initials: H
authors.lastname: Aoki