Real space pairing within the strong correlation limit of the Anderson model

Abstract

We present a model calculation for phonon induced attractive interactions among heavy fermions on a single cubic lattice. The formation of heavy quasi-particles in the Anderson lattice is described with the help of the slave-boson concept within the mean field approximation. The Kondo volume concept is used to derive interactions between heavy fermions and phonons. Then, with varying electron-phonon coupling strength, determined by an enhancement factor η, the self-consistent solutions lead to competing superconducting states with different symmetries. In a first approach, a quite general k-dependence of the electron-phonon interaction is considered. In this case, Cooper pairs with s-like symmetry dominate for small values of η, while pairs withd _γ-like symmetry are favoured with increase in η. In a second approach, by restricting the electron-phonon interactions to those, whose coupling functions solely depend on momentum transfer, we obtain in addition pairs with p-like symmetry. In this case,d _γ-like pairing can be strongly suppressed, and pairs with s- or p-like symmetry can dominate.