Quasicondensation and coherence in the quasi-two-dimensional trapped Bose gas

2008/04/30 by R. N. Bisset, Matthew J. Davis, M. J. Davis +3
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Quantum, superfluid, helium dynamics #Strong Light-Matter Interactions #cond-mat.other #cond-mat.quant-gas

paper · pdf · doi:10.1103/physreva.79.033626

published as Phys. Rev. A 79, 033626 (2009) · 9 pages, 7 figures

openalex publication_date 2009/03/30 · arxiv created 2011/08/30 · arxiv updated 2011/08/31 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

We simulate a trapped quasi-two-dimensional Bose gas using a classical field method. To interpret our results we identify the uniform Berezinskii-Kosterlitz-Thouless (BKT) temperature T_BKT as where the system phase-space density satisfies a critical value. We observe that density fluctuations are suppressed in the system well above T_BKT when a quasicondensate forms as the first occurrence of degeneracy. At lower temperatures, but still above T_BKT, we observe the development of appreciable coherence as a prominent finite-size effect, which manifests as bimodality in the momentum distribution of the system. At T_BKT algebraic decay of off-diagonal correlations occurs near the trap center with an exponent of 0.25, as expected for the uniform system. Our results characterize the low-temperature phase diagram for a trapped quasi-two-dimensional Bose gas and are consistent with observations made in recent experiments.

Citations

• Projected Gross-Pitaevskii equation theory of finite-temperature collective modes for a trapped Bose gas
• Transition from the Bose–Einstein condensate to the Berezinskii–Kosterlitz–Thouless phase
• Existence of Long-Range Order in One and Two Dimensions
• Two-point correlations of a trapped interacting Bose gas at finite temperature
• Numerical method for evolving the projected Gross-Pitaevskii equation
• Kosterlitz-Thouless Transition of the Quasi-Two-Dimensional Trapped Bose Gas
• Calculation of the microcanonical temperature for the classical Bose field
• Ordering, metastability and phase transitions in two-dimensional systems
• Critical Temperature of a Trapped Bose Gas: Comparison of Theory and Experiment