Signatures of interactions in the Andreev spectrum of nanowire Josephson junctions

TL;DR

This study uses microwave spectroscopy to explore the complex Andreev spectra in InAs nanowire Josephson junctions, revealing effects of Coulomb interactions and spin-orbit coupling.

Contribution

It provides new experimental evidence of Coulomb interactions in Andreev spectra, expanding understanding beyond non-interacting models.

Findings

Identification of Coulomb interaction signatures in spectra

Observation of spin-orbit interaction effects on transition lines

Qualitative agreement between experiments and models

Abstract

We performed microwave spectroscopy of an InAs nanowire between superconducting contacts implementing a finite-length, multi-channel Josephson weak link. Certain features in the spectra, such as the splitting by spin-orbit interactions of the transition lines among Andreev states, have been already understood in terms of non-interacting models. However, we identify here additional transitions, which evidence the presence of Coulomb interactions. By combining experimental measurements and model calculations, we reach a qualitative understanding of these very rich Andreev spectra.