First and second sound in a highly elongated Fermi gas at unitarity

Year: 2013

Authors: Hou Y.H., Pitaevskii L.P., Stringari S.

Autors Affiliation: Dipartimento di Fisica, Università di Trento and INO-CNR BEC Center, I-38123 Povo, Italy; Kapitza Institute for Physical Problems RAS, Kosygina 2, 119334 Moscow, Russia

Abstract: We consider a Fermi gas at unitarity trapped by a highly elongated harmonic potential and solve the equations of two fluid hydrodynamics at finite temperature. The propagation of sound waves as well as the discretized solutions in the presence of weak axial trapping are considered. The relevant thermodynamic functions entering the hydrodynamic equations are discussed in the superfluid and normal regimes in terms of universal scaling functions. Both first sound and second sound solutions are calculated as a function of temperature and the role of the superfluid density is explicitly pointed out. The density fluctuations in the second sound wave are found to be large enough to be measured as a consequence of the finite thermal expansion coefficient of the gas. Emphasis is given to the comparison with recent experimental data.


Volume: 88 (4)      Pages from: 043630  to: 043630

More Information: The authors would like to acknowledge systematic discussions and fruitful collaborations with R. Grimm, M. J. H. Ku, E. R. Sanchez Guajardo, L. A. Sidorenkov, M. K. Tey, and M. W. Zwierlein. We are grateful to M. J. H. Ku and M. W. Zwierlein for providing the relevant experimental data characterizing the universal functions of the unitary Fermi gas, systematically employed in the present paper. L. P. P. wishes to thank P. Hoheneberg for an insightful discussion. This work has been supported by ERC through the QGBE grant and by the Italian MIUR through the PRIN-2009 grant.
DOI: 10.1103/PhysRevA.88.043630

Citations: 21
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