Low-temperature transport through a quantum dot coupled to two superconducting leads

We calculate the nonlinear dc conductance as well as the total current through a nonequilibrium quantum dot coupled to two superconducting leads. We show that the Kondo effect manifests itself in the appearence of two bound states inside the superconducting gap $[-2\Delta ,2\mathrm{}\Delta ]$ and discuss the influence of these bound states on the transport properties of the dot. The relation to the real systems is also briefly considered.