Tunable Josephson supercurrent through a two level quantum dot superconductor tunnel junction

The present paper deals with the study of Josephson supercurrent across a two level quantum dot (QD) sandwiched between the s-wave superconductors. The renormalized Anderson model used that includes the contribution towards attractive BCS type effective interaction in the superconducting leads responsible for s-wave pairing, electron tunneling energy term representing coupling of superconducting leads with the dot energy levels responsible for Josephson Cooper pair tunneling between two superconductors. The Green’s function meanfield technique is employed within the framework of Ambegaokar–Baratoff approach to analyze the Josephson supercurrent across such a junction. It is pointed out that the Josephson supercurrent is suppressed when additional QD level(s) are switched on.