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Claude Cohen Tannoudji

Prix Nobel en 1997 pour le ralentissement et le piégeage des atomes par la lumière laser.

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Accueil du site > Thèses et habilitations > Thermal and superfluid properties of the two-dimensional Bose gas

Thermal and superfluid properties of the two-dimensional Bose gas

Soutenance de thèse de Rémi Desbuquois (LKB)

Lundi 3 juin 2013 à 10h30, en salle E244 ( Conf IV ) à l’Ecole Normale Supérieure, 24 rue Lhomond Paris 75005.

Thèse réalisée au Laboratoire Kastler Brossel sous la direction de Jean Dalibard.

Summary :

The physical properties of a homogeneous system at the thermodynamic equilibrium are strongly constrained by its dimensionality. In this respect, the two dimensional Bose gas constitutes a particularly interesting system : while it is impossible to observe a long range order at non-zero temperatures, there exists nevertheless a phase transition to a superfluid state at low temperatures. Furthermore, owing to the reduced dimensionality, the equation of state of the weakly interacting two-dimensional Bose gas is scale invariant.

In this thesis, we present an experimental study of the two-dimensional Bose gas. We measure its equation of state with two different methods, and find a good agreement with analytic and numerical predictions. These results confirm as well the scale invariance of the system. Furthermore, one of the methods allows for a determination of the equation of state with a single adjustable parameter. We then characterize the superfluid response of the system., by showing evidence for a dissipationless response of the system to a moving perturbation. Finally, we analyze the fluctuations dynamics of the 2D Bose gas, which confirms both the suppression of density fluctuations in the superfluid phase, and the dominating contribution of phonons to the phase fluctuations.

Post-scriptum :

Département de Physique de l’École Normale Supérieure
Laboratoire Kastler Brossel
24 rue Lhomond 75005 Paris
Tel. Bureau : +331 44 32 33 07
Tel. Labo : +331 44 32 25 87

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