Josephson effect between a two-band superconductor with s++ or s± pairing symmetry and a conventional s-wave superconductor

Abstract

In this work, we investigate the Josephson effect between a two-band superconductor either with the s++ (two energy gaps have the same sign and are fully gapped) pairing symmetry or s± (two energy gaps have π phase difference and are fully gapped) pairing symmetry and a conventional s-wave superconductor. The ground state, critical current, plasma modes, flux-flow dynamics, response to external ac electric field, and possible soliton solutions are investigated. For junctions with the charge neutrality breaking, we find a new plasma mode for junctions, which gives rise to new resonance peaks in the Josephson flux-flow region. Because of the frustrated interaction in junctions with s± pairing symmetry, time-reversal symmetry (TRS) can be broken if the frustration is optimized. In the TRS broken (TRSB) state, there is a nontrivial phase difference between the two Josephson tunneling channels, which results in a nontrivial interference. Furthermore, we find a massless plasma mode at the TRSB transition for junctions with the charge neutrality breaking. In the TRSB state, a spontaneous magnetic flux appears where there is a spatial inhomogeneity in the Josephson coupling, thus providing a possible smoking-gun evidence for the underlying pairing symmetry.

Source-reported materials — not catalogue approval

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