On the theory of superconductivity of mixed valence and heavy fermion systems

Abstract

The effective mass and the superconducting transition temperature of mixed valence and heavy fermion systems are discussed under formally equivalent Hamiltonians in the quasiparticle picture. Linearization is applied to the correlation term between up- and down-spin ƒ electrons on the same site. Mixing between ƒ and conduction electrons is decoupled through the Bogoliubov transformation. Numerical results show that proper mixing and correlation enhance the effective mass of these systems. In mixed valence system, both ƒ and conduction electrons make contributions to superconductivity, but basically only ƒ electrons are responsible for superconductivity in heavy fermion system.