Superconducting instabilities in the finite U Anderson lattice model

We have investigated superconducting instabilities in the finite U Anderson lattice model within the Zou-Anderson slave boson representation in the Kondo lattice limit appropriate for heavy fermion systems. We found Cooper instability in the p channel and a repulsion in both the s and d channels. Based on the above mechanism of pairing, we have derived a ratio of the Gruneisen parameters Γ(Tc)/Γ(TK) which can be negative or positive, consistent with the experimental data. This result cannot be achieved in the U = ∞ limit, which gives only positive values for this ratio.