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Claude Cohen Tannoudji

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

Ses travaux sont à la source des recherches actuelles de l'IFRAF.



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Accueil du site > Séminaires > LKB > Reprise des séminaires du groupe « atomes froids » du LKB : Emergence of coherence in a uniform quasi-2D Bose gas

Reprise des séminaires du groupe « atomes froids » du LKB : Emergence of coherence in a uniform quasi-2D Bose gas

par Tom Bienaim

Mercredi 17 septembre 2014 de 9h30 à 10h30 salle de conférence 46 rue d’Ulm 75005 Paris

Resume

While ultra-cold gases have been traditionally confined in harmonic potentials, trapping atoms in spatially uniform potentials has recently received growing interest as it opens up new possibilities to measure long-range correlations or study the dynamics of phase transitions by looking at the establishment of phase\ coherence over the entire system. I will first describe our experimental setup which consists of a Bose-gas in an in-plane « box-potential » plus a harmonic confinement out of plane (frequency nu_z). Whereas most 2D experiments rely on completely freezing out one spatial degree of freedom (k_B*T << h*nu_z), I will discuss how dimensionality can be reduced at much higher temperatures (k_B*T > h*nu_z) by Bose condensing to lower dimensions. I will present evidence of this transverse condensation by looking at the in-plane coherence of the gas.

I will then report on a series of experiments where we study the dynamics of the coherence establishment by imposing a temperature quench on the system across the transverse condensation transition. I will show that it leads to the stochastic nucleation of topological defects (vortices) and I will compare measurements of their distribution for different cooling rate with predictions based on the Kibble-Zurek.

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