[Réflexions sur les fluides quantiques dipolaires]
Nous donnons une description thermodynamique des gaz froids en interaction dipolaire qui tient compte de la longue portée de ces interactions et de leur absence d’invariance par rotation. Elle fait intervenir un champ thermodynamique supplémentaire conjugué à l’extension linéaire du gaz selon la direction des dipôles. La pression uniaxiale associée se manifeste par un écart à la relation de Gibbs–Duhem dans le profil de densité du gaz piégé. Elle doit s’annuler dans les gouttelettes (des états liés du système), une condition qui détermine la dépendance observée du rapport d’aspect avec le nombre de particules. Une généralisation tensorielle du théorème du viriel et un certain nombre d’autres relations thermodynamiques exactes sont obtenues. Enfin, en étendant un modèle dû à Nozières, on aboutit à un critère simple pour la transition de solidification vers une onde de densité de masse superfluide.
We present a thermodynamic description of ultracold gases with dipolar interactions which properly accounts for the long-range nature and broken rotation invariance of the interactions. It involves an additional thermodynamic field conjugate to the linear extension of the gas along the direction of the dipoles. The associated uniaxial pressure shows up as a deviation from the Gibbs–Duhem relation in the density profile of a trapped gas. It has to vanish in self-bound droplets, a condition which determines the observed dependence of the aspect ratio on particle number. A tensorial generalization of the virial theorem and a number of further exact thermodynamic relations are derived. Finally, extending a model due to Nozières, a simple criterion for the freezing transition to a superfluid mass density wave is given.
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Mots-clés : Atomes froids, Fluides dipolaires, Supersolides, Limite thermodynamique, Interactions à longue portée
Wilhelm Zwerger 1
CC-BY 4.0
@article{CRPHYS_2024__25_G1_389_0,
author = {Wilhelm Zwerger},
title = {Reflections on dipolar quantum fluids},
journal = {Comptes Rendus. Physique},
pages = {389--413},
publisher = {Acad\'emie des sciences, Paris},
volume = {25},
year = {2024},
doi = {10.5802/crphys.222},
language = {en},
}
Wilhelm Zwerger. Reflections on dipolar quantum fluids. Comptes Rendus. Physique, Volume 25 (2024), pp. 389-413. doi : 10.5802/crphys.222. https://comptes-rendus.academie-sciences.fr/physique/articles/10.5802/crphys.222/
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