Superconductivity in the extended two-dimensional Hubbard model: Strong-coupling regime and hybridization effects

In this work we have considered a two-dimensional two-band Hubbard model (extended Hubbard model) to study the effect of the nonlocal hybridization V-k on the superconductivity. In the strong-coupling regime and for a d-wave superconducting gap, we have obtained the superconducting critical temperature T-c and the zero-temperature superconducting gap Delta(0) for different hybridizations. We have adopted hopping parameters suitable to describe the high-temperature superconductor materials. The results show that for a fixed value of the hybridization and the intraband d-d attractive potential U, the gap increases for low temperatures and diminishes as the temperatures increase toward T-c. As the hybridization increases both, Delta(0) and T-c, diminish. For each hybridization, the quantity 2 Delta(0)/k(B)T(c) increases and saturates in a particular value as U increases. The relation between applied pressure P and hybridization in the strong-coupling regime is also discussed.