Condens. Matter, Volume 5, Issue 1 (March 2020) – 22 articles
Cover Story (view full-size image): Spectra of collective excitations in atomic superfluids provide valuable information on their internal states. Different geometries and effective dimensionalities have been realized for ultracold gases. In our work, the sound velocity and the damping rate of the collective excitations of a 2D fermionic superfluid are determined in a non-perturbative manner. Specifically, we focus on the Anderson–Bogoliubov excitations in the BEC-BCS crossover regime. The calculation is performed within the path-integral formalism and the Gaussian pair fluctuation approximation. We derive the propagator of the collective excitations and determine their dispersion relation by locating its complex poles. Also we calculate the response functions which can be used as another way to determine the sound velocity and the damping rate. View this paper.
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