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A: Fachverband Atomphysik

A 1: Quantengase (jointly with Q)

A 1.3: Vortrag

Montag, 19. März 2007, 11:00–11:15, 6J

Critical behavior of a trapped interacting Bose gas — •Tobias Donner, Stephan Ritter, Thomas Bourdel, Ferdinand Brennecke, Anton Öttl, Michael Köhl, and Tilman Esslinger — Institut für Quantenelektronik, ETH Zürich, 8093 Zürich, Schweiz

In the vicinity of a phase transition minute variations in the controlling parameters can dramatically change the properties of a system. Using a trapped Bose gas we have entered the critical regime of Bose-Einstein condensation and gained access to its beyond mean-field physics. This regime is characterized by fluctuations extending far beyond the thermal de Broglie wavelength: The length scale over which the system behaves coherently diverges, which is directly reflected in the shape of the spatial first order correlation function.

Using matter-wave interference we measure the correlation length of these fluctuations as a function of temperature. We study the divergence of the correlation length of the order parameter as the temperature approaches the critical point and determine its critical exponent for a trapped, weakly interacting Bose gas to be ν=0.67±0.13.