Current and shot noise in superconducting junctions with a quantum dot in the Kondo regime

Transport through an Anderson impurity in the Kondo regime situated between two superconductors is considered. Here the analysis is performed within the slave boson mean field approximation. The new physics follows due to multiple Andreev reflections at the boundary between the dot and superconductor. The important new parameter which enters the transport characteristics is the ratio of the Kondo temperature to the superconducting gap. The current, shot noise power are displayed versus the applied bias voltage in the subgap region and found to be strongly dependent on this ratio. In particular, the I–V curve exposes an excess current in the limit of high Kondo temperature.