| Issue |
EPL
Volume 114, Number 6, June 2016
|
|
|---|---|---|
| Article Number | 60005 | |
| Number of page(s) | 5 | |
| Section | General | |
| DOI | https://doi.org/10.1209/0295-5075/114/60005 | |
| Published online | 15 July 2016 | |
Hydrodynamic spectrum of a superfluid in an elongated trap
1 Laboratoire Kastler Brossel, ENS-PSL Research University, CNRS, UPMC, Collège de France - 24, rue Lhomond, 75005 Paris, France
2 Département de physique, École Polytechnique - 91128 Palaiseau cedex, France
3 Laboratoire de Physique Statistique, École Normale Supérieure, PSL Research University, Université Paris Diderot Sorbonne Paris-Cité, Sorbonne Universités UPMC Univ Paris 06, CNRS - 24 rue Lhomond, 75005 Paris, France
Received: 1 June 2016
Accepted: 29 June 2016
In this article we study the hydrodynamic spectrum of a superfluid confined in cylindrical trap. We show that the dispersion relation 
of the phonon branch scales like 
at large q, leading to a vanishingly small superfluid critical velocity. In practice the critical velocity is set by the breakdown of the hydrodynamic approximation. For a broad class of superfluids, this entails a reduction of the critical velocity by a factor 
with respect to the free-space prediction (here 
is the trapping frequency and 
the chemical potential of the cloud).
PACS: 03.75.Kk – Dynamic properties of condensates; collective and hydrodynamic excitations, superfluid flow / 03.75.Ss – Degenerate Fermi gases / 37.10.Gh – Atom traps and guides
© EPLA, 2016
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