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arXiv 1202.5869cond-mat.quant-gas
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波混沌作为玻色-爱因斯坦凝聚体耗尽的特征

Wave chaos as signature for depletion of a Bose-Einstein condensate

Iva Brezinova, Axel U. J. Lode, Alexej I. Streltsov, Ofir E. Alon, Lorenz S. Cederbaum, Joachim Burgdörfer

摘要:

研究了一维浅势场中排斥相互作用玻色-爱因斯坦凝聚体的膨胀。我们表明,这些系统中的Gross-Pitaevskii方程(GPE),即在希尔伯特空间的两个附近的凝聚波函数的指数分离的发病波混沌的发病,可以被用来作为指示的BEC的耗尽和占领内的多体描述的激发模式的发病。多组态含时Hartree玻色子(MCTDHB)方法和GPE之间的比较揭示了一个广泛的单粒子外部势的耗尽多体效应和波混沌的平均场效应之间的密切对应关系。在波动混沌中,GPE不能解释精细尺度的量子涨落,因为超出GPE有效性的多体效应是不可忽略的。令人惊讶的是,尽管GPE未能解释耗尽,但单粒子密度的粗粒度期望值(如原子云的总宽度)与多体模拟非常一致。冷凝物的时间依赖性消耗可以通过实验研究,例如,通过膨胀的原子云的相干性的衰减。

英文摘要:

We study the expansion of repulsively interacting Bose-Einstein condensates (BECs) in shallow one-dimensional potentials. We show for these systems that the onset of wave chaos in the Gross-Pitaevskii equation (GPE), i.e. the onset of exponential separation in Hilbert space of two nearby condensate wave functions, can be used as indication for the onset of depletion of the BEC and the occupation of excited modes within a many-body description. Comparison between the multiconfigurational time-dependent Hartree for bosons (MCTDHB) method and the GPE reveals a close correspondence between the many-body effect of depletion and the mean-field effect of wave chaos for a wide range of single-particle external potentials. In the regime of wave chaos the GPE fails to account for the fine-scale quantum fluctuations because many-body effects beyond the validity of the GPE are non-negligible. Surprisingly, despite the failure of the GPE to account for the depletion, coarse grained expectation values of the single-particle density such as the overall width of the atomic cloud agree very well with the many-body simulations. The time dependent depletion of the condensate could be investigated experimentally, e.g., via decay of coherence of the expanding atom cloud.

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