Andreev quantum dot with several conducting channels

TL;DR

This paper investigates an Andreev quantum dot with multiple conducting channels, analyzing its ground state degeneracy, charge, and Josephson current, revealing potential for sensitive magnetic flux detection and transistor applications.

Contribution

It provides a detailed analysis of multi-channel Andreev quantum dots, including Coulomb interactions, and explores their enhanced sensitivity for practical quantum device applications.

Findings

Sensitivity increases with the number of channels

Coulomb interactions affect degeneracy and charge

Potential use as magnetic flux detector or Josephson transistor

Abstract

We study an Andreev quantum dot, that is a quantum dot inserted in a superconducting ring, with several levels or conducting channels. We analyze the degeneracy of the ground state as a function of the phase difference and of the gate voltage and find its dependence on the Coulomb interaction within and between channels. We compute a (non integer) charge of the dot region and Josephson current. The charge-to-phase and current-to-gate voltage sensitivities are studied. We find that, even in the presence of Coulomb interaction between the channels, the sensitivity increases with the number of channels, although it does not scale linearly as in the case with no interactions. The Andreev quantum dot may therefore be used as a sensitive detector of magnetic flux or as a Josephson transistor.