Coexistence of spin polarization and pairing correlations in metallic grains

We investigate the competition between magnetic depairing interactions, due to spin-exchange mechanism and∕or to spin-dependent asymmetric bandwidths, and pairing coupling in metallic grains. We present a detailed analysis of the quantum ground state in different regimes arising from the interplay between ferromagnetic and pairing correlations for different fillings. We find out that the occurrence of a ground state with coexisting spin-polarization and pairing correlations is enhanced when the asymmetric spin-dependent distribution of the single-particle energies is considered. The mechanisms leading to such a stable quantum state are finally clarified.