Supercurrent in a double quantum dot

TL;DR

This paper reports the experimental observation of the Josephson effect in a double quantum dot system, revealing a honeycomb stability pattern and ground state transitions, consistent with the two-impurity Anderson model.

Contribution

First demonstration of supercurrent in a double quantum dot with detailed correlation to theoretical models.

Findings

Honeycomb pattern in supercurrent stability diagram

Discontinuities in critical current at ground state transitions

Maximum critical current at zero energy level detuning

Abstract

We demonstrate the Josephson effect in a serial double quantum dot defined in a nanowire with epitaxial superconducting leads. The supercurrent stability diagram adopts a honeycomb pattern with electron-hole and left-right reflection symmetry. We observe sharp discontinuities in the magnitude of the critical current, $I_c$, as a function of dot occupation, related to doublet to singlet ground state transitions. Detuning of the energy levels offers a tuning knob for $I_c$, which attains a maximum at zero detuning. The consistency between experiment and theory indicates that our device is a faithful realization of the two-impurity Anderson model.