Resonant Andreev Scattering In Phase-Coherent, Superconducting Nanostructures

Analytic predictions for resonant transport in three generic structures are presented. For a structure comprising a normal (N) contact - normal dot (NDOT) - superconducting (S) contact, we predict that finite voltage, differential conductance resonances are destroyed by the switching on of superconductivity in the S-contact. In the weak coupling limit, the surviving resonances have a double-peaked line-shape. Secondly, we demonstrate that resonant Andreev interferometers can provide galvonometric magnetic flux detectors, with a sensitivity in excess of the flux quantum. Finally, for a superconducting dot (SDOT) connected to normal contacts (N), we show that the onset of superconductivity can increase the sub-gap conductance, in contrast with the usual behaviour of a tunnel junction.