Nonlinearity in normal-metal–superconductor transport: Scattering-matrix approach

G. B. Lesovik; A. L. Fauch`ere; G. Blatter

doi:10.1103/PhysRevB.55.3146

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Nonlinearity in normal-metal–superconductor transport: Scattering-matrix approach

G. B. Lesovik, A. L. Fauch`ere, G. Blatter

DOI 10.1103/PhysRevB.55.3146 · Physical Review B

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Abstract

A general formula for the current through a disordered normal-superconducting junction is derived, which is valid at finite temperature and includes the full voltage dependence. The result depends on a multichannel scattering matrix, which describes elastic scattering in the normal region, and accounts for the Andreev scattering at the normal-metal–superconductor interface. The symmetry of the current with respect to sign reversal in the subgap regime is discussed. The Andreev approximation is used to derive a spectral conductance formula, which applies to voltages both below and above the gap. In a case study the spectral conductance formula is applied to the problem of a normal-metal–insulator–normal-metal–insulator–superconductor double barrier junction.