Josephson systems based on ballistic point contacts between single-band and multi-band superconductors

TL;DR

This paper investigates the Josephson effect in ballistic point contacts between single-band and multi-band superconductors, revealing frustration and multiple energy minima, and explores the behavior of dc SQUIDs based on these junctions, providing tools for detecting multi-band structures and BTRS.

Contribution

It introduces the analysis of Josephson junctions involving multi-band superconductors and demonstrates how their unique properties affect SQUID behavior, aiding experimental detection of multi-band and BTRS states.

Findings

Josephson junctions become frustrated with multiple energy minima.

Behavior of dc SQUIDs varies with multi-band superconductor type.

Features in critical current and magnetic flux dependences differ from conventional SQUIDs.

Abstract

The Josephson effect in ballistic point contacts between single-band and multi-band superconductors was investigated. It was found that in the case of Josephson junctions formed by a single-band and an $s_\pm$-wave two-band superconductor as well as by a single-band and a three-band superconductor the junctions become frustrated, demonstrating the $\phi$-contact properties. Depending on the ground state of a three-band superconductor with broken time-reversal symmetry (BTRS), the Josephson junction can have from one to three energy minima, some of which can be locally stable. We also study the behavior of a dc SQUID based on the Josephson junctions between single-band and multi-band superconductors. Some features on the dependences of the critical current and the total magnetic flux on the applied flux of a dc SQUID based on the Josephson point contacts between a single-band superconductor and an $s_\pm$-wave superconductor, three-band superconductor with BTRS and three-band superconductor without BTRS as compared to the conventional dc SQUIDs based on single-band superconductors were found. The results can be used as an experimental tool to detect the existence of multi-band structure and BTRS.