First and second sound in a strongly interacting Fermi gas

Abstract

Using a variational approach, we solve the equations of two-fluid hydrodynamics for a uniform and trapped Fermi gas at unitarity. In the uniform case, we find that the first and second sound modes are remarkably similar to those in superfluid Helium, a consequence of strong interactions. In the presence of harmonic trapping, first and second sound become degenerate at certain temperatures. At these points, second sound hybridizes with first sound and is strongly coupled with density fluctuations, giving a promising way of observing second sound. We also discuss the possibility of exciting second sound by generating local heat perturbations.

Published version. 7 pages, 4 figures

References in corpus (7)

• Theory of ultracold Fermi gases
• Strongly paired fermions: Cold atoms and neutron matter
• Finite-Temperature Collective Dynamics of a Fermi Gas in the BEC-BCS Crossover
• Thermodynamics of a Trapped Unitary Fermi Gas
• Is a gas of strongly interacting atomic fermions a nearly perfect fluid?
• Temperature of a trapped unitary Fermi gas at finite entropy
• Variational theory of two-fluid hydrodynamic modes at unitarity