Interaction effects in superconductor–normal quantum dot–superconductor structures

We consider a system consisting of two macroscopic superconductors coupled to each other through a weak link that incorporates a non-superconducting two-dimensional quantum dot. We find that Coulomb interactions between mid-gap states and electrons in the quantum dot give rise to a new phase-dependent contribution to the total energy of the system, and hence to the supercurrent. Since the number of electrons confined in the quantum dot depends on the gate voltage Vg, even the supercurrent can be controlled with Vg.