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- Variational theory of two-fluid hydrodynamic modes at unitarity
- Taylor, E.; Hu, H.; Liu, X.-J.; Griffin, A.
- We present the results of a variational calculation of the frequencies of the low-lying Landau two-fluid hydrodynamic modes in a trapped Fermi superfluid gas at unitarity. Landau's two-fluid hydrodynamics is expected to be the correct theory of Fermi superfluids at finite temperatures close to unitarity, where strong interactions give rise to collisional hydrodynamics. Two-fluid hydrodynamics predicts the existence of in-phase modes in which the superfluid and normal fluid components oscillate together, as well as out-of-phase modes where the two components move against each other. We prove that, at unitarity, the dipole and breathing in-phase modes are locally isentropic. Their frequencies are independent of temperature and are the same above and below the superfluid transition, a feature due as much to the harmonic trapping potential as to the thermodynamic properties at unitarity. The out-of-phase modes, in contrast, are strongly dependent on temperature and hence can be used to test the thermodynamic properties and superfluid density of a Fermi gas at unitarity. We give numerical results for the frequencies of these modes as function of temperature in an isotropic trap at unitarity.
- Publication type
- Journal article
- Physical Review A: Atomic, Molecular, and Optical Physics, Vol. 77, no. 3 (Mar 2008), article no. 033608
- Publication year
- FOR Code(s)
- 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0204 Condensed Matter Physics; 0205 Optical Physics
- Charge trapping; Fermi level; Hydrodynamics; Isotropic trap; Phase transitions; Two phase flow; Two-fluid hydrodynamic; Variational techniques; Variational theory
- American Physical Society
- Publisher URL
- Copyright © 2008 The American Physical Society. The accepted manuscript of the paper is reproduced here for noncommerical purposes only in accordance with the copyright policy of the publisher.
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