Proximity-induced transport in superconductor-normal metal nanostructures

We calculate the conductance for a diffusive normal wire (N) in contact with a superconductor (S). Using a numerical scattering matrix approach and a quasiclassical Green function technique, we compare the conductance G of the system connected to two normal reservoirs when the superconductor is in its normal state with the conductance G_s in the superconducting state and predict that the difference δG = G_s - G may be negative or positive depending upon the S/N interface resistance and the interface resistance at the ends of the N wire. As the temperature T is varied, δG(T) may change sign and exhibit two maxima.