MESOSCOPIC NORMAL METAL-SUPERCONDUCTOR JUNCTION SYSTEMS - THE EFFECTIVE ACTION APPROACH

Single electron charging effects in systems containing small normal an d superconducting islands have recently attracted much interest. The t heoretical description of these effects usually involves a perturbatio n theory in the tunneling conductance. While this perturbation theory can be developed on a case-by-case basis, the effective action approac h provides a unified and transparent formulation. We use this approach to discuss single electron tunneling, Andreev reflection, the proximi ty effect and the supercurrent through normal-superconductor systems i n the presence of charging effects. We also show that in a real-time f ormulation the effective action approach can be used to calculate sing le electron tunneling and co-tunneling rates.