Gapless Higgs Mode in the Fulde-Ferrell-Larkin-Ovchinnikov State of a Superconductor

TL;DR

This paper predicts a stable, detectable gapless Higgs mode in Fulde-Ferrell-Larkin-Ovchinnikov superconducting states, arising from translation symmetry breaking, unlike the heavy Higgs mode in uniform superconductors.

Contribution

It demonstrates the existence of a gapless Higgs mode in FFLO states using phenomenological and microscopic BCS models, a novel finding in superconductor physics.

Findings

Gapless Higgs mode exists in FFLO states.

The mode is stable and detectable.

Originates from translation symmetry breaking.

Abstract

The Higgs mode associated with amplitude fluctuations of the superconducting gap in uniform superconductors usually is heavy, which makes its excitation and detection difficult. We report on the existence of a gapless Higgs mode in the Fulde-Ferrell-Larkin-Ovchinnikov states. This feature is originated from the Goldstone mode associated with the translation symmetry breaking. The existence of the gapless Higgs mode is demonstrated by using both a phenomenological model and microscopic Bardeen-Cooper-Schrieffer (BCS) theory. The gapless Higgs mode can avoid the decay into other low energy excitations, which renders it stable and detectable.