Josephson Interference due to Orbital States in a Nanowire Proximity Effect Junction

TL;DR

This paper reports on experimental observations of Josephson interference caused by orbital states in a nanowire junction, revealing a novel multi-band effect that influences supercurrent modulation under magnetic fields.

Contribution

It introduces a semi-classical multi-band model explaining the orbital-induced Josephson interference observed in Nb-InAs nanowire junctions.

Findings

Critical current oscillations due to orbital states were observed.

A semi-classical model successfully reproduces experimental data.

Orbital effects dominate over spin-orbit and Zeeman effects in this system.

Abstract

The Josephson supercurrent in a Nb-InAs nanowire-Nb junction was studied experimentally. The nanowire goes superconducting due to the proximity effect, and can sustain a phase coherent supercurrent. An unexpected modulation of the junction critical current in an axial magnetic field is observed, which we attribute to a novel form of Josephson interference, due to the multi-band nature of the nanowire. Andreev pairs occupying states of different orbital angular momentum acquire different superconducting phases, producing oscillations of the critical current versus magnetic flux. We develop a semi-classical multi-band model that reproduces the experimental data well. While spin-orbit and Zeeman effects are predicted to produce similar behaviour, the orbital effects are dominant in the device studied here. This interplay between orbital states and magnetic field should be accounted for in the study of multi-band nanowire Josephson junctions, in particular, regarding the search for signatures of topological superconductivity in such devices.