Anomalous modulation of Josephson radiation in nanowire-based Josephson junctions

TL;DR

This study explores how magnetic fields influence Josephson radiation in nanowire-based junctions, revealing anomalous behaviors that could aid in probing topological states.

Contribution

It demonstrates magnetic field-induced modulation of Josephson radiation spectra in nanowire junctions, linking these effects to changes in the superconducting circuit environment.

Findings

Josephson emission follows expected frequency at zero field

Deviations and enhancements occur above 300 mT magnetic field

Modulations are attributed to trivial circuit changes, not topological effects

Abstract

We investigate the Josephson radiation of nanowire (NW)-based Josephson junctions in a parallel magnetic field. The Josephson junction made of an InAs NW with superconducting Al leads shows the emission spectra which follow the Josephson frequency $f_{J}$ over the range 4-8 GHz at zero magnetic field. We observe an apparent deviation of the emission spectra from the Josephson frequency which is accompanied by a strong enhancement of the switching current above a magnetic field of $\sim 300$ mT. The observed modulations can be understood to reflect trivial changes in the superconducting circuit surrounding the device which is strongly affected by the applied magnetic field. Our findings will provide a way to accurately investigate topological properties in NW-based systems.