Laboratoire de Physique Théorique
Toulouse - UMR 5152

I will report a study on the combined effect of thermal and quantum fluctuations in a zero dimensional superconductor. By using path integral techniques, a novel expressions for the partition function is obtained as well as the superconducting order parameter which include both types of fluctuations. These results are valid for any temperature and to leading order in \delta/\Delta_0 where \delta is the mean level spacing and \Delta_0 is the bulk energy gap. Divergences arising at low temperatures, previously reported in the literature, are avoided by identifying and treating non-perturbatively a low-energy collective mode. In the low and high temperature limit our results agrees with those from the random phase (RPA) and the static path approximation (SPA) respectively.