Séminaire (physique) "Quench-induced vortices in a uniform Bose gas"

Organisé par l'Institut Nonlinéaire de Nice. Par Tom Bienaimé ENS - Paris
Quand ? Le 04-07-2014,
de 11:00 à 11:00
Où ? Institut Nonlinéaire de Nice, 361 routes des Lucioles, Sophia Antipolis, Valbonne
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Quench-induced vortices in a uniform Bose gas

While ultra-cold gases have been traditionally confined into harmonic potentials, trapping atoms in spatially uniform potentials has recently received growing interest as they open up new perspectives to simulate many-body systems. To further explore the physics of two-dimensional Bose gases in which our group has a long standing interest, we have developed a technique to confine an atomic gas in a 2D "box potential" with arbitrary geometry. After presenting the experimental setup, I will discuss a series of experiments where we study temperature quenches of a Bose gas across the normal-to-superfluid transition for two different geometries: an annulus and a square.

Quenches across a phase transition lead to the stochastic production of topological defects as it was put forward by Kibble and Zurek. In the annular geometry these topological defects are quantized supercurrents, whose amplitude and chirality are measured by a new interferometric method. For the square, the topological defects manifest themselves as free "bulk" vortices which are revealed using a standard time-of-flight technique. I will demonstrate the stochastic nature of these topological defects and I will compare measurements of their distribution for different quench times with predictions based on the Kibble-Zurek mechanism.