Geometry-related magnetic interference patterns in longSNSJosephson junctions

Abstract

We have measured the critical current dependence on the magnetic flux of two long $SNS$ junctions differing by the normal wire geometry. The samples are made by a Au wire connected to W contacts, via focused ion beam assisted deposition. We could tune the magnetic pattern from the monotonic Gaussian-like decay of a quasi-one-dimensional (1D) normal wire to the Fraunhofer-like pattern of a square normal wire. We explain the monotonic limit with a semiclassical 1D model, and we fit both field dependencies with numerical simulations of the two-dimensional Usadel equations. Furthermore, we observe both integer and fractional Shapiro steps. The magnetic flux dependence of the integer steps reproduces as expected that of the critical current ${I}_{c}$, while fractional steps decay slower with the flux than ${I}_{c}$.