Fluxon Dynamics of a Long Josephson Junction with Two-gap Superconductors

TL;DR

This paper explores the complex phase dynamics in long Josephson junctions with two-gap superconductors, revealing how interband effects lead to modulated critical currents and electromagnetic radiation emission.

Contribution

It introduces the concept of stable 2π-phase textures caused by interband Josephson effects and analyzes their impact on vortex behavior and electromagnetic emission.

Findings

Critical current becomes spatially and temporally modulated.

Josephson vortex trajectories are altered by phase textures.

Electromagnetic radiation is emitted during vortex passage.

Abstract

We investigate the phase dynamics of a long Josephson junction (LJJ) with two-gap superconductors. In this junction, two channels for tunneling between the adjacent superconductor (S) layers as well as one interband channel within each S layer are available for a Cooper pair. Due to the interplay between the conventional and interband Josephson effects, the LJJ can exhibit unusual phase dynamics. Accounting for excitation of a stable 2$\pi$-phase texture arising from the interband Josephson effect, we find that the critical current between the S layers may become both spatially and temporally modulated. The spatial critical current modulation behaves as either a potential well or barrier, depending on the symmetry of superconducting order parameter, and modifies the Josephson vortex trajectories. We find that these changes in phase dynamics result in emission of electromagnetic waves as the Josephson vortex passes through the region of the 2$\pi$-phase texture. We discuss the effects of this radiation emission on the current-voltage characteristics of the junction.