Superconductivity Due to Interband Attraction: Competition between Diagonal and Off-Diagonal Long-Range Orders

Abstract

The phase diagram for spin 1/2 fermions with attractive interband interactions (−V) is obtained for the two-band Hubbard model in the space of −V, intraband repulsion (U), and the band filling from the quantum Monte Carlo calculation along with the mean-field theory in one dimension. The competition of an off-diagonal long-range order with diagonal orders (CDW and SDW) is shown to result in a superconducting ground state arising from interband pairing (i) in the presence of U of right magnitude (∼V) and (ii) in non-half-filled bands.