准二维囚禁玻色气体的准凝聚和相干性
Quasicondensation and coherence in the quasi-two-dimensional trapped Bose gas
摘要：
我们用经典场方法模拟了准二维玻色气体的囚禁。为了解释我们的结果，我们确定了均匀的Berezinskiii-Kosterlitz无（BKT）温度$T_{BKT}$的系统相空间密度满足一个临界值。我们观察到，密度波动被抑制在系统远高于$T_{BKT}$时，准冷凝形式作为第一次发生的简并。在较低的温度下，但仍然高于$T_{BKT}$，我们观察到的发展可观的相干性作为一个突出的有限尺寸效应，表现为双峰的动量分布的系统。在$T_{BKT}$，非对角相关的代数衰减发生在陷阱中心附近，指数为0.25，正如均匀系统所预期的那样。我们的结果表征了低温相图的准二维玻色气体被困，并在最近的实验中所作的观察是一致的。
英文摘要：
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 quasi-condensate 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-2D Bose gas and are consistent with observations made in recent experiments.
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