Gapless Higgs mode in the Fulde-Ferrell-Larkin-Ovchinnikov state of a superconductor

The Higgs mode associated with amplitude fluctuations of the superconducting gap in uniform superconductors is usually 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 originates from the Goldstone mode associated with 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.

Automated summary

This study reports the existence of a gapless Higgs mode in the Fulde-Ferrell-Larkin-Ovchinnikov states. The Higgs mode associated with amplitude fluctuations of the superconducting gap is usually heavy, but in this particular state, it becomes gapless. The existence of the gapless Higgs mode is demonstrated and it is found to be more stable and detectable.