Superconductivity in an extended Hubbard model with attractive interaction

Abstract

In this work, a two-dimensional one-band Hubbard model is investigated withina two-pole approximation. The model presents a non-local attractive potentialU (U < 0) that allows the study of d-wave superconductivity and also includes hopping up tosecond-nearest neighbors. The two-pole scheme has been proposed to improve theHubbard-I approximation. The analytical results show a more complex form for the gapΔ(T), when compared to the one obtained in the latter approximation. Indeed, new anomalouscorrelation functions associated with the superconductivity are involved in the calculation ofΔ(T). Numerical results in a range of temperatures are presented. Moreover, the structure of thequasiparticle bands and the topology of the Fermi surface are studied in detail inthe normal state. Connections with some experimental results are also included.