Sheet-current distribution in a dc SQUID washer probed by vortices

TL;DR

This paper introduces a new LTSEM-based vortex imaging technique to directly visualize sheet-current distributions in dc SQUID washers, providing a more direct and accurate method than previous magnetic field inversion approaches.

Contribution

The authors develop and validate a novel vortex imaging method that directly maps current distributions in dc SQUID washers using pinned vortices as local detectors.

Findings

LTSEM vortex signals relate directly to the scalar stream function J

The method yields results in good agreement with numerical calculations

It offers a more direct approach compared to previous magnetic field inversion techniques

Abstract

We present a novel method, based on vortex imaging by low-temperature scanning electron microscopy (LTSEM), to directly image the sheet-current distribution in YBa2Cu3O7 dc SQUID washers. We show that the LTSEM vortex signals are simply related to the scalar stream function describing the vortex-free circulating sheet-current distribution J. Unlike previous inversion methods that infer the current distribution from the measured magnetic field, our method uses pinned vortices as local detectors for J. Our experimental results are in very good agreement with numerical calculations of J.