Resonant Andreev Scattering In Phase-Coherent, Superconducting Nanostructures

TL;DR

This paper analytically studies resonant transport in superconducting nanostructures, revealing how superconductivity affects conductance resonances, proposes flux detection using Andreev interferometers, and shows superconductivity can enhance sub-gap conductance.

Contribution

It provides new analytic predictions for resonant transport behaviors in various superconducting nanostructures, including effects of superconductivity on conductance and flux detection capabilities.

Findings

Superconductivity destroys certain differential conductance resonances in N-NDOT-S structures.

Resonant Andreev interferometers can detect magnetic flux with high sensitivity.

Superconducting dots can increase sub-gap conductance, contrary to typical tunnel junction behavior.

Abstract

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.