Bragg spectroscopy and pair-breaking-continuum mode in a superfluid Fermi gas

TL;DR

This paper predicts a new collective excitation mode in superfluid Fermi gases that can be observed via Bragg spectroscopy by measuring changes in the order parameter, providing a novel way to probe superfluid properties.

Contribution

The study introduces a theoretical prediction of a pair-breaking continuum mode in superfluid Fermi gases observable through Bragg spectroscopy, focusing on the order parameter response.

Findings

Mode is observable in frequency, width, and spectral weight

Response measured on the order parameter modulus reveals the mode

Predicted in the long wavelength limit at zero temperature

Abstract

The superfluid, pair condensed spin-1/2 Fermi gases are supposed to exhibit at nonzero wave vector a still unobserved collective excitation mode in their pair-breaking continuum. Using BCS theory at zero temperature and in the long wavelength limit, we predict that this mode is quantitatively observable (in frequency, width and spectral weight) in the response of a cold atom gas to a laser Bragg excitation, if one measures the perturbation induced on the order parameter modulus rather than on the density.