The fluctuating and dissipative dynamics of matter-wave dark solitons within harmonically trapped, partially condensed Bose gases is studied both numerically and analytically. A study of the stochastic Gross-Pitaevskii equation, which correctly accounts for density and phase fluctuations at finite temperatures, reveals dark-soliton decay times to be lognormally distributed at each temperature, thereby characterizing the previously predicted long-lived soliton trajectories within each ensemble of numerical realizations [S. P. Cockburn , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.174101 104, 174101 (2010)]. Expectation values for the average soliton lifetimes extracted from these distributions are found to agree well with both numerical and analytic predictions based upon the dissipative Gross-Pitaevskii model (with the same ab initio damping). Probing the regime for which 0.8 kBT<μ<1.6 kBT, we find average soliton lifetimes to scale with temperature as τ∼T-4, in agreement with predictions previously made for the low-temperature regime kBT≪μ. The model is also shown to capture the experimentally relevant decrease in the visibility of an oscillating soliton due to the presence of background fluctuations.
Physical Review A
- Pub Date:
- October 2011
- Ultracold gases trapped gases;
- Tunneling Josephson effect Bose-Einstein condensates in periodic potentials solitons vortices and topological excitations;
- Condensed Matter - Quantum Gases
- 17 pages, 14 figures