Multiband superconductivity: A mapping to the extended attractive Hubbard model

Abstract

Following our recent work which shows that purely repulsive multiband systems effectively reduce to the extended attractive Hubbard model having the on-site repulsion along with nearest-neighbor$(\tilde V)$ and next-nearst-neighbor$(\tilde W)$ attraction for the cuprate structures, we study the latter model in the mean-field theory.T _c against band filling for various symmetries of pairing is numerically calculated. The results show that, for the region of$\tilde V$ and$\tilde W$ expected for the mapping from the original multiband model,T _c has maximum values of the order of 100 K, which is consistent with the experimental results. For certain values of parameters,s- and$d_{x^2 - y^2 }$-wave pairing have similar values of T_c, which may suggest the possibility of a mixed phase of the two.