Theory of vortex structure in Josephson junctions with multiple tunneling channels: Vortex enlargement as a probe of $\pm s$-wave superconductivity

TL;DR

This paper develops a theoretical framework for Josephson vortex structures in multigap superconductors with multiple tunneling channels, revealing vortex enlargement as a signature of $ ext{±}s$-wave pairing symmetry.

Contribution

It introduces coupled sine-Gordon equations for multichannel Josephson junctions and demonstrates vortex enlargement as a probe for $ ext{±}s$-wave superconductivity.

Findings

Vortex magnetic field distribution is more enlarged in $ ext{±}s$-wave than in s-wave.

Cancellation of multiple Josephson currents causes vortex enlargement.

Proposes experimental evaluation of vortex enlargement as a superconductivity probe.

Abstract

We theoretically study Josephson vortex structures in Josephson junctions which have multiple tunneling channels caused by multiple superconducting gaps. Deriving "coupled sine-Gordon equations" from the free-energy taking account of the multiple tunneling channels, we examine two typical situations, a heterotic junction composed of multigap-superconductor, insulator, and single-gap superconductor, and a grain-boundary junction formed by two identical multigap superconductors. Then, we reveal in both situations that the magnetic field distribution of the Josephson vortex for $\pm s$-wave superconductivity is more enlarged than that for s-wave without sign change between the order parameters. Its mechanism is ascribed to a cancellation of the multiple Josephson currents. We display such an anomalous Josephson vortex and suggest how to evaluate the enlargement.