Negative superfluid density: Mesoscopic fluctuations and reverse of the supercurrent through a disordered Josephson junction

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

doi:10.1103/PhysRevB.65.012504

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Negative superfluid density: Mesoscopic fluctuations and reverse of the supercurrent through a disordered Josephson junction

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

DOI 10.1103/PhysRevB.65.012504 · Physical Review B

T1

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Abstract

We calculate the Josephson coupling energy UJ(φ) [related to the supercurrent I=(2e/ħ)dUJ/dφ] for a disordered normal metal between two superconductors with a phase difference φ. We demonstrate that the symmetry of the scattering matrix of noninteracting quasiparticles in zero magnetic field implies that UJ(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.