On the Josephson Coupling between a disk of one superconductor and a surrounding superconducting film of a different symmetry

TL;DR

This paper models a Josephson junction between a d-wave superconductor disk and a different symmetry superconducting film, revealing vortex formation and providing insights into the nature of superconductivity in complex materials.

Contribution

It introduces a model for a Josephson junction with spatially varying coupling, analyzing vortex formation and critical current, relevant for understanding superconductor symmetry.

Findings

System always introduces Josephson vortices to lower energy.

Calculated critical current for the junction.

Recent experiments could be explained by d-wave symmetry.

Abstract

A cylindrical Josephson junction with a spatially dependent Josephson coupling which averages to zero is studied in order to model the physics of a disk of d-wave superconductor embedded in a superconducting film of a different symmetry. It is found that the system always introduces Josepshon vortices in order to gain energy at the junction. The critical current is calculated. It is argued that a recent experiment claimed to provide evidence for s-wave superconductivity in $YBa_2Cu_3O_7$ may also be consistent with d-wave superconductivity. Figures available from the author on request.