Quasiparticle trapping at vortices producing Josephson supercurrent enhancement

TL;DR

This paper investigates how quasiparticle trapping at vortices can enhance Josephson supercurrent in superconducting devices under magnetic fields, highlighting non-topological mechanisms relevant for quantum qubit design.

Contribution

It demonstrates that quasiparticle trapping by vortices, rather than topological transitions, can cause supercurrent enhancement in superconducting junctions under magnetic fields.

Findings

Supercurrent enhancement observed in InAs nanowire Josephson junctions.

Hysteresis in switching current indicates quasiparticle trapping effects.

Non-topological quasiparticle trapping can mimic topological signatures.

Abstract

The Josephson junction of a strong spin-orbit material under a magnetic field is a promising Majorana fermion candidate. Supercurrent enhancement by a magnetic field has been observed in the InAs nanowire Josephson junctions and assigned to a topological transition. In this work we observe a similar phenomenon but discuss the non-topological origin by considering trapping of quasiparticles by vortices that penetrate the superconductor under a finite magnetic field. This assignment is supported by the observed hysteresis of the switching current when sweeping up and down the magnetic field. Our experiment shows the importance of quasiparticles in superconducting devices with a magnetic field, which can provide important insights for the design of quantum qubits using superconductors.