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

R Bisset, M Davis, Tapio Simula, P Blakie

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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 TBKT as where the system phase-space density satisfies a critical value. We observe that density fluctuations are suppressed in the system well above TBKT when a quasicondensate forms as the first occurrence of degeneracy. At lower temperatures, but still above TBKT, 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 TBKT 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.
Original languageEnglish
Pages (from-to)033626-1 - 033626-8
Number of pages8
JournalPhysical Review A
Volume79
Issue number3
DOIs
Publication statusPublished - 2009
Externally publishedYes

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