Scattering of light and atoms in a Fermi-Dirac gas with BCS pairing

TL;DR

This paper investigates how superfluidity in a Fermi-Dirac gas affects its optical properties, including scattering, susceptibility, and Bragg diffraction, highlighting the impact of BCS pairing on these phenomena.

Contribution

It provides a theoretical analysis of quantum-statistical corrections and the influence of BCS pairing on optical responses in a superfluid Fermi gas.

Findings

BCS pairing enhances incoherent scattering processes.

Superfluidity causes broadening and shifting of absorption linewidth.

Superfluidity significantly increases the static structure function in Bragg spectroscopy.

Abstract

We theoretically study the optical properties of a Fermi-Dirac gas in the presence of a superfluid state. We calculate the leading quantum-statistical corrections to the standard column density result of the electric susceptibility. We also consider the Bragg diffraction of atoms by means of light-stimulated transitions of photons between two intersecting laser beams. Bardeen-Cooper-Schrieffer pairing between atoms in different internal levels magnifies incoherent scattering processes. The absorption linewidth of a Fermi-Dirac gas is broadened and shifted. Bardeen-Cooper-Schrieffer pairing introduces a collisional local-field shift that may dramatically dominate the Lorentz-Lorenz shift. For the case of the Bragg spectroscopy the static structure function may be significantly increased due to superfluidity in the nearforward scattering.