Controlling the Sign of Magnetoconductance in Andreev Quantum Dots

TL;DR

This paper develops a theory for quantum transport in Andreev quantum dots, revealing how conductance corrections can change sign based on lead channels or magnetic flux, with implications for experimental magnetoconductance behavior.

Contribution

It introduces a comprehensive theoretical framework for understanding sign changes in conductance corrections in Andreev quantum dots due to magnetic flux and lead channels.

Findings

Quantum correction to conductance can change sign depending on channels or flux.

Magnetic flux influences the sign of conductance correction, not just its magnitude.

Experimental signatures include non-monotonic magnetoconductance and temperature dependence transition.

Abstract

We construct a theory of coherent transport through a ballistic quantum dot coupled to a superconductor. We show that the leading-order quantum correction to the two-terminal conductance of these Andreev quantum dots may change sign depending on (i) the number of channels carried by the normal leads or (ii) the magnetic flux threading the dot. In contrast, spin-orbit interaction may affect the magnitude of the correction, but not always its sign. Experimental signatures of the effect include a non-monotonic magnetoconductance curve and a transition from an insulator-like to a metal-like temperature dependence of the conductance. Our results are applicable to ballistic or disordered dots.