Measurement of critical current flow and connectivity in systems of joined square superconducting plates

TL;DR

This paper introduces a magneto-optical imaging method to measure electrical connectivity in systems of joined superconducting plates by analyzing current flow discontinuities caused by weak links.

Contribution

It presents a novel imaging-based technique to quantify electrical connectivity between superconducting plates with weak links, demonstrated on Nb films with focused ion beam modifications.

Findings

Current flow patterns reveal connectivity levels.

Discontinuity lines indicate weak link effects.

Method applicable to superconducting systems with weak interfaces.

Abstract

A method to measure the electrical connectivity between square superconducting plates joined by weak link interfaces is presented. It is based on observation of lines where the flow of critical current abruptly changes direction due to the presence of weak links, and the confinement created by the shape of the sample. The method is demonstrated using magneto-optical imaging (MOI) of systems consisting of up to 2 X 2 plates joined to form a larger square. Common features are found in the current flow patterns, which allow to measure the electrical connectivity between the plates by observing an angle between pairs of lines indicating where the current abruptly changes flow direction, so-called discontinuity, or d-lines. The samples used in this study are Nb films with weak links created by focused ion beam machining.