SPIN SINGLET AND TRIPLET SUPERCONDUCTIVITY INDUCED BY CORRELATED HOPPING INTERACTIONS

Abstract

In this article, we show that the Bardeen-Cooper-Schrieffer (BCS) formalism applied to a Hubbard model is capable to predict the s-, p- and d-wave superconductivity within a single theoretical scheme. This study is performed on a square lattice described by a generalized Hubbard Hamiltonian, in which correlated-hopping interactions are included in addition to the repulsive Coulombic one. Within the BCS formalism using a variable chemical potential, the superconducting ground states are determined by two coupled integral equations, whose integrand functions have main contributions around the Fermi surface. We observe the existence of a maximum critical temperature for s-, p- and d-wave superconducting channels that occur at the medium, low and high electron densities, respectively. Furthermore, the p- and d-wave superconducting specific heats show a power-law temperature dependence, instead of the exponential one for the s channel. Finally, the smallness of the anisotropic single-energy-excitation-gap minima is essential for the specific heat behavior, and this fact allows to understand the experimental data obtained from Sr2RuO4 and La2-xSrxCuO4 superconductors.