Highly transparent superconducting - normal junctions in a homogeneous superconductor induced by local fields of magnetic domains

TL;DR

This paper demonstrates the creation of highly transparent, tunable superconducting-normal junctions within a single superconductor using magnetic domain fields, revealing evidence of Andreev reflection and interface transparency.

Contribution

It introduces a method to induce and study superconducting-normal junctions within a homogeneous superconductor using magnetic domain fields, highlighting high interface transparency.

Findings

Evidence of Andreev reflection at the junctions

High transparency of superconductor-normal interfaces

Controlled nucleation of superconductivity above magnetic domains

Abstract

Using the highly inhomogeneous fields of a magnetic substrate, tunable junctions between superconducting and normal state regions were created inside a thin film superconductor. The investigation of these junctions, created in the same material, gave evidence for the occurrence of Andreev reflection, indicating the high transparency of interfaces between superconducting and normal state regions. For the realization of this study, a ferromagnet with magnetic stripe domains was used as a substrate, on top of which a superconducting transport bridge was prepared perpendicular to the underlying domains. The particular choice of materials allowed to restrict the nucleation of superconductivity to regions above either reverse-domains or domain walls. Moreover, due to the specific design of the sample, transport currents in the superconductor passed through a sequence of normal and superconducting regions.