Abstract
Anisotropic superconductivity of strongly correlated electrons is studied in the 1⁄d expansion, with d being the spatial dimensionality. Kondo-effect-type local spin fluctuations are of the leading order in 1⁄d. They are responsible for the formation of Gutzwiller’s heavy electrons. Superconductivity is of higher order in 1⁄d. The superexchange interaction causes superconductivity of s or dγ wave, while a three-site exchange interaction causes that of s or p wave. Within the mean-field approximation which is one of the simplest schemes of the 1⁄d expansion, the highest critical temperature is obtained for dγ wave, two dimensions, and almost half filling where the effective mass of heavy electrons is large and the three-site exchange interaction is relatively ineffective through the enhancement of vertex functions for spin channels. An argument is given in connection with high-Tc superconductivity in the cuprate oxides.
