Constructing classical field for a Bose-Einstein condensate in arbitrary trapping potential; quadrupole oscillations at nonzero temperatures

Abstract

We optimize the classical field approximation of the version described in J. Phys. B 40, R1 (2007) for the oscillations of a Bose gas trapped in a harmonic potential at nonzero temperatures, as experimentally investigated by Jin et al. [Phys. Rev. Lett. 78, 764 (1997)]. Similarly to experiment, the system response to external perturbations strongly depends on the initial temperature and on the symmetry of perturbation. While for lower temperatures the thermal cloud follows the condensed part, for higher temperatures the thermal atoms oscillate rather with their natural frequency, whereas the condensate exhibits a frequency shift toward the thermal cloud frequency (m=0 mode), or in the opposite direction (m=2 mode). In the latter case, for temperatures approaching critical, we find that the condensate begins to oscillate with the frequency of the thermal atoms, as in the m=0 mode. A broad range of frequencies of the perturbing potential is considered.

10 pages, 9 figures, added references, changed content, improved English

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• The superfluid fountain effect in a Bose-Einstein condensate
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• Classical fields in the one-dimensional Bose gas: applicability and determination of the optimal cutoff
• Continuum of classical-field ensembles from canonical to grand canonical and the onset of their equivalence
• Complex wave fields in the interacting one-dimensional Bose gas
• Free expansion of a Bose-Einstein condensate at the presence of a thermal cloud
• Density fluctuations in a quasi-one-dimensional Bose gas as observed in free expansion
• Condensate losses and oscillations induced by Rydberg atoms