Effect of local correlations on s-wave symmetry superconductivity

We derive superconducting mean-field equations for an attractive interaction V in the s-wave channel when local Coulomb interactions are taken into account for any value of U. Results show that Coulomb repulsion diminishes the critical temperature T-c to the order parameter Delta (T) for values of U greater than or equal to \V\. Furthermore, the results are also quite sensible to band filling. In the presence of local correlations, 2 Delta (O)/T-c differs from the BCS ratio since Coulomb interactions affect much more superconducting critical temperature T-c than superconducting order parameter Delta (T). Some consequences of our findings for experimental measurements in narrow band systems are discussed.