Charge Pumping in Mesoscopic Systems coupled to a Superconducting Lead

TL;DR

This paper develops a scattering-matrix formula to analyze charge pumping in mesoscopic systems connected to superconductors, revealing how Andreev reflection can significantly enhance pumped currents.

Contribution

The paper introduces a general scattering-matrix approach for pumped current in mesoscopic systems with superconducting leads, including specific calculations for various device configurations.

Findings

Andreev reflection can boost pumped current by up to a factor of 4

Asymmetric coupling further increases current enhancement

Derived formula applicable to multiple mesoscopic device types

Abstract

We derive a general scattering-matrix formula for the pumped current through a mesoscopic region attached to a normal and a superconducting lead. As applications of this result we calculate the current pumped through (i) a pump in a wire, (ii) a quantum dot in the Coulomb blockade regime, and (iii) a ballistic double-barrier junction, all coupled to a superconducting lead. Andreev reflection is shown to enhance the pumped current by up to a factor of 4 in case of equal coupling to the leads. We find that this enhancement can still be further increased for slightly asymmetric coupling.