KONDO EFFECT COUPLED TO SUPERCONDUCTIVITY IN ULTRASMALL GRAINS

We investigate the Kondo effect and superconductivity in ultrasmall grains by using a model, which consists of sd and BCS Hamiltonians with the introduction of a pseudofermion. We discuss physical properties of the condensation energy and behavior of the gap function and the spin singlet order parameter corresponding to the Kondo effect in relation to the critical level spacing and coexistence. We find that strong local magnetic moments from the impurities makes the transition temperature for superconductivity reduced. However, weak couplings lambda of the superconductivity do not destroy the spin singlet order parameter at all. Finally we derive the exact equation for the Kondo regime in nanosystem and discuss the condensation energy from the viewpoint of the energy level.