Variety of c-axis collective excitations in layered multigap superconductors

TL;DR

This paper develops a dynamical theory for phase differences in layered multigap superconductors, predicting unique collective excitations including Leggett modes, which differ from those in single-gap systems.

Contribution

It introduces a novel theoretical framework for understanding collective excitations in multigap layered superconductors, highlighting the existence of Leggett modes.

Findings

Prediction of Leggett mode excitations in multigap superconductors

Explicit dispersion relations for collective modes

Demonstration of unique properties of Leggett modes

Abstract

We present a dynamical theory for the phase differences along a stacked direction of intrinsic Josephson junctions (IJJ's) in layered multigap superconductors, motivated by the discovery of highly-anisotropic iron-based superconductors with thick perovskite-type blocking layers. The dynamical equations describing AC and DC intrinsic Josephson effects peculiar to multigap IJJ's are derived, and collective Leggett mode excitations in addition to the Josephson plasma established in single-gap IJJ's are predicted. The dispersion relations of their collective modes are explicitly displayed, and the remarkable peculiarity of the Leggett mode is demonstrated.