Propagation of Second sound in a superfluid Fermi gas in the unitary limit

Abstract

We study sound propagation in a uniform superfluid gas of Fermi atoms in the unitary limit. The existence of normal and superfluid components leads to appearance of two sound modes in the collisional regime, referred to as first and second sound. The second sound is of particular interest as it is a clear signal of a superfluid component. Using Landau's two-fluid hydrodynamic theory, we calculate hydrodynamic sound velocities and these weights in the density response function. The latter is used to calculate the response to a sudden modification of the external potential generating pulse propagation. The amplitude of a pulse which is proportional to the weight in the response function, is calculated the basis of the approach of Nozieres and Schmitt-Rink (NSR) for the BCS-BEC crossover. We show that, in a superfluid Fermi gas at unitarity, the second sound pulse is excited with an appreciate amplitude by density perturbations.

12 pages, 9 figures. This version includes an erratum concerning the temperature dependence of hydrodynamic sound weights in Phys. Rev. A 80, 043613 (2009)

References in corpus (6)

• Weakly bound dimers of fermionic atoms
• Collective excitations of a degenerate gas at the BEC-BCS crossover
• Pairing fluctuations and the superfluid density through the BCS-BEC crossover
• Temperature of a trapped unitary Fermi gas at finite entropy
• Sound propagation in elongated superfluid fermion clouds
• Variational theory of two-fluid hydrodynamic modes at unitarity

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• Second sound and the density response function in uniform superfluid atomic gases
• First and second sound in cylindrically trapped gases
• Second sound in 2D Bose gas: from the weakly interacting to the strongly interacting regime
• Shell-shaped atomic gases
• Pair excitations and parameters of state of imbalanced Fermi gases at finite temperatures
• Low-momentum dynamic structure factor of a strongly interacting Fermi gas at finite temperature: A two-fluid hydrodynamic description
• Propagation of first and second sound in a two-dimensional Fermi superfluid
• Translational-invariant bipolarons and superconductivity
• Superconducting properties of 3D low-density TI-bipolaron gas in magnetic field
• Dynamic Structure Factor of Normal Fermi Gas from Collisionless to Hydrodynamic Regime
• Two-fluid theory for superfluid system with anisotropic effective masses