Theory of heterotic SIS Josephson junctions between single- and multi-gap superconductors

TL;DR

This paper develops a theoretical framework for heterotic SIS Josephson junctions involving single- and multi-gap superconductors, revealing unique collective modes and symmetry-dependent properties.

Contribution

It introduces a novel theory predicting collective oscillation modes and symmetry effects in heterotic Josephson junctions between single- and multi-gap superconductors.

Findings

Identification of in-phase and out-of-phase collective modes

Reduction of Josephson plasma frequency for ± s-wave symmetry

Critical current and Fraunhofer pattern dependence on superconductor symmetry

Abstract

Using the functional integral method, we construct a theory of heterotic SIS Josephson junctions between single- and two-gap superconductors. The theory predicts the presence of in-phase and out-of-phase collective oscillation modes of superconducting phases. The former corresponds to the Josephson plasma mode whose frequency is drastically reduced for $\pm$ s-wave symmetry, and the latter is a counterpart of Leggett's mode in Josephson junctions. We also reveal that the critical current and the Fraunhofer pattern strongly depend on the symmetry type of the two-gap superconductor.