Multiband, moderate U approach to high temperature superconductivity in oxides

Abstract

We investigate a two-band superconductor model taking into account the interband BCS-like matrix elements originating in the exchange-like integral K at each atomic site as well as the usual intraband BCS interaction and the on-site Coulomb energy U. A mean field treatment reveals that K diminishes the effect of U, elevating T c substantially if K ≲ U. When K > U, it drives superconductivity with no other pairing agents. Values of the exchange-like integrals for Cu d- and O p-orbitals are tabulated. Relevance to the high T c in oxide superconductors is briefly discussed.