Superconductivity in the Anderson lattice: a finite-U slave boson description

Using the Kotliar and Ruckenstein slave boson formalism we consider the finite-U Anderson lattice. We study the appearance of superconductivity as a function of the Coulomb repulsion, density and f-level location for s-wave and d-wave pairing symmetries. The results extend previous studies where the infinite-U limit was considered, confirming that superconductivity remains as the Coulomb coupling increases, if the attractive interaction is not weak. Superconductivity disappears for large U as the filling of the heavy particles approaches one, as expected. Since U is finite, superconductivity occurs, in general, for any band-filling being depressed near half-filling, particularly for d-wave symmetry.