Superconductor-quantum dot-superconductor junction in the Kondo regime

Electron transport between two superconductors through an Anderson impurity in the Kondo regime is investigated within the slave boson mean-field approximation. The current, shot-noise power and Fano factor are displayed versus the applied bias voltage in the subgap region and found to be strongly dependent on the ratio between the Kondo temperature $T_K$ and the superconducting gap $\Delta .$ In particular, the $I-V$ curve exposes an excess current in the limit $T_K/\Delta \gg 1.$