Can mesoscopic fluctuations reverse the supercurrent through a disordered Josephson junction?

Titov, M.; Jacquod, Ph.; Beenakker, C. W. J.

Can mesoscopic fluctuations reverse the supercurrent through a disordered Josephson junction?

Authors

Titov, M.

Jacquod, Ph.

Beenakker, C. W. J.

Description

We calculate the Josephson coupling energy $U_J(ϕ)$ (related to the supercurrent $I=(2e/\hbar) dU_J/dϕ$) for a disordered normal metal between two superconductors with a phase difference $ϕ$. We demonstrate that the symmetry of the scattering matrix of non-interacting quasiparticles in zero magnetic field implies that $U_J(ϕ)$ has a minimum at $ϕ=0$. A maximum (that would lead to a $π$-junction or negative superfluid density) is excluded for any realization of the disorder.
2 pages