Superconductivity in a strongly correlated one-band system.

Abstract

We study superconductivity in the extended Hubbard model with a strong on-site repulsion U and weak attractive density-density interaction ${\mathit{V}}_{\mathit{ij}}$. The electron correlation effects, beyond the weak-coupling regime of U, are included approximately by employing Hubbard decoupling approximations. The formulas for superconducting transition temperature ${\mathit{T}}_{\mathit{c}}$ of the present approach are compared to those obtained with the strong-coupling expansion and slave-boson techniques. The methods share some common features. We discuss behavior of ${\mathit{T}}_{\mathit{c}}$ for superconducting phases with s- and d-wave symmetry of the superconducting order parameter. In contrast to the mean-field treatment of U, we find that the strong on-site repulsion does not destroy superconductivity induced by ${\mathit{V}}_{\mathit{ij}}$0 even when U\ensuremath{\gg}|${\mathit{V}}_{\mathit{ij}}$|. \textcopyright{} 1996 The American Physical Society.