Hannover 2010 – scientific programme

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A: Fachverband Atomphysik

A 23: Poster II

A 23.36: Poster

Thursday, March 11, 2010, 16:30–19:00, Lichthof

The thermal Bose gas - a stochastic approach — •Sigmund Heller and Walter T. Strunz — TU Dresden

Temperature dependent quantities like spatial correlation functions [1,2] density fluctuations [3] and interference contrast [4] are measured in current experiments with ultracold Bose gases. In order to describe these experiments, we present a novel stochastic evolution equation which enables us to obtain the thermal state of the canonical ensemble. The equation provides a full quantum field description and therefore does not suffer from cutoff problems which often occur for classical field equations. Furthermore, it is possible to solve the equation in position space - no knowledge of eigenfunctions or eigenenergies of the external potential is required. The equation is derived for the non interacting case, but drawing on analogies with the classical case, it is more than tempting to include the interaction in a mean field sense. Apart from exact results that we obtain for the ideal gas case, we show calculations for an interacting gas in one and three dimensions and obtain good agreement with experimental [2] and theoretical [5,6] work. Results for ground state occupancy, spatial correlation functions and equilibrium density profiles are presented.

[1] I. Bloch et al., Nature 403, 166 (2000).

[2] S. Hofferberth et al., Nature 4, 489-495 (2008).

[3] J. Esteve et al., Phys. Rev. Lett. 96, 130403 (2006).

[4] R. Gati et al., Phys. Rev. Lett. 96, 130404 (2006).

[5]S. Giogini et al., Phys. Rev. A 54, 4633 (1996).

[6] A. Imambekov et al., Phys Rev. A 80, 033604 (2009).