We study the influence of quantum fluctuations on the phase, density, and pair correlations in a trapped quasicondensate after a quench of the interaction strength. To do so, we derive a description similar to the stochastic Gross-Pitaevskii equation (SGPE) but keeping a fully quantum description of the low-energy fields using the positive-P representation. This allows us to treat both the quantum and thermal fluctuations together in an integrated way. A plain SGPE only allows for thermal fluctuations. The approach is applicable to such situations as finite temperature quantum quenches, but not equilibrium calculations due to the time limitations inherent in positive-P descriptions of interacting gases. One sees the appearance of antibunching, the generation of counter-propagating atom pairs, and increased phase fluctuations. We show that the behavior can be estimated by adding the T = 0 quantum fluctuation contribution to the thermal fluctuations described by the plain SGPE.
Journal of Physics B Atomic Molecular Physics
- Pub Date:
- July 2016
- Condensed Matter - Quantum Gases
- 17 pages, 18 figures. Major revision, basically a reboot. Equations are now derived rather than heuristically postulated, and the example quench is now physically realistic. The calculations presented are new, but overall results are mostly qualitatively similar. A better understanding of the interplay between quantum and thermal fluctuations has been reached