High magnetic field stability in a planar graphene-NbSe$_2$ SQUID

TL;DR

This paper demonstrates a stable, atomically thin van der Waals SQUID with high in-plane magnetic field resilience, enabling detailed analysis of supercurrent distributions and revealing a stable conductance channel.

Contribution

The work introduces a novel planar graphene-NbSe$_2$ SQUID that remains stable at high magnetic fields and develops numerical methods to analyze current distributions from interference patterns.

Findings

Stable operation up to 4.5 T in high in-plane magnetic fields.

Identification of a stable, narrow conductance channel.

Field-driven transition in supercurrent distribution.

Abstract

Thin NbSe$_2$ retains superconductivity at high in-plane magnetic field up to 30 T. In this work we construct an atomically thin, all van der Waals SQUID, in which current flows between NbSe$_2$ contacts through two parallel graphene weak links. This fully planar device remains uniquely stable at high in-plane field. This enables tracing the evolution of the critical current interference patterns as a function of the field up to 4.5 T, allowing nm-scale sensitivity to deviations from a perfect atomic plane. We present numerical methods to retrieve asymmetric current distributions J$_0$ from measured interference maps, and suggest a new application of the dual junction geometry to probe the current density in the absence of phase information. The interference maps exhibit a striking field-driven transition, indicating a redistribution of supercurrents to narrow channels. Our results suggest the existence of a preferred conductance channel with an exceptional stability to in-plane magnetic field.