Wednesday, June 5, 2013

1306.0398 (J. Armaitis et al.)

Quantum rotor model for a Bose-Einstein condensate of dipolar molecules    [PDF]

J. Armaitis, R. A. Duine, H. T. C. Stoof
We show that a Bose-Einstein condensate of heteronuclear molecules in the regime of small and static electric fields is described by a quantum rotor model for the macroscopic electric dipole moment of the molecular gas cloud. We solve this model exactly and compare the results of this exact calculation with the usual Gross-Pitaevskii mean-field theory for Bose-Einstein condensation. This comparison shows that qualitative and experimentally observable differences exist between exact and mean-field results due to the crucial role of quantum fluctuations. In particular, the non-zero dipole moment predicted by mean-field theory is quenched by the latter fluctuations in a large part of the phase diagram. Investigation of the wavefunction of the macroscopic dipole moment reveals squeezing of the probability distribution.
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