Eur. Phys. J. D 17, 49-55 (2001)
https://doi.org/10.1007/s100530170036

Dynamic structure factor of a superfluid Fermi gas

¹ Istituto Nazionale di Fisica della Materia and Classe di Scienze, Scuola Normale Superiore, piazza dei Cavalieri 7, 56126 Pisa, Italy
² Istituto Nazionale di Fisica della Materia and European Laboratory for Non-Linear Spectroscopy, Università di Firenze, largo E. Fermi 2, 50125 Firenze, Italy
³ Laboratoire Kastler-Brossel, École Normale Supérieure, 24 rue Lhomond, 75231 Paris, France

Corresponding author: ^a minguzzi@sns.it

Received: 28 March 2001
Published online: 15 October 2001

Abstract

We describe the excitation spectrum of a two-component neutral Fermi gas with attractive interactions in the superfluid phase at finite temperature by deriving a suitable Random-Phase approximation in the collisionless regime with the technique of functional derivatives. The obtained spectrum for the homogeneous gas at small wavevectors contains the Bogoliubov-Anderson phonon and is essentially different from the spectrum predicted by the static Bogoliubov theory, which instead shows an unphysically large response. We adapt the results for the homogeneous system to obtain the dynamic structure factor of a harmonically confined superfluid and we identify in the spectrum a unique feature of the superfluid phase.