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arXiv 1712.04428cond-mat.quant-gas
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壳状凝聚体的静态和动态性质

Static and dynamic properties of shell-shaped condensates

Kuei Sun, Karmela Padavić, Frances Yang, Smitha Vishveshwara, Courtney Lannert

摘要:

中空系统的静态、动态和拓扑性质不同于那些由于与内表面相关联的边界的存在而被完全填充的中空系统。空心玻色-爱因斯坦凝聚体(BEC)自然存在于各种超冷原子系统中,也可能存在于中子星中,但由于重力凹陷,迄今为止还没有在地球上孤立地实验实现。在国际空间站冷原子实验室微重力条件下首次实现全封闭BEC壳的预期动机下,我们对球对称空心BEC以及通过中心密度耗尽从填充球BEC到薄壳的中空过渡进行了全面研究。我们采用互补的分析和数值技术,以研究平衡密度分布和集体模式结构的冷凝壳托管的一系列捕获潜力。我们确定具体和强大的签名的演变从填充到空心结构和出现的内边界的影响,包括在呼吸模式类型的集体模式频率和整个过渡的表面模式结构的重组下降。通过将我们的分析扩展到一个盘到环的二维过渡,我们表明集体模式签名是中空的一个基本特征,独立于特定的几何形状。最后,我们将我们的工作与过去和正在进行的实验努力,并考虑薄凝壳重力的影响。我们确定的条件下,重力凹陷是高度破坏性的,并研究这些壳的集体模式的微重力模式混合效应。

英文摘要:

Static, dynamic, and topological properties of hollow systems differ from those that are fully filled as a result of the presence of a boundary associated with an inner surface. Hollow Bose-Einstein condensates (BECs) naturally occur in various ultracold atomic systems and possibly within neutron stars but have hitherto not been experimentally realized in isolation on Earth because of gravitational sag. Motivated by the expected first realization of fully closed BEC shells in the microgravity conditions of the Cold Atomic Laboratory aboard the International Space Station, we present a comprehensive study of spherically symmetric hollow BECs as well as the hollowing transition from a filled sphere BEC into a thin shell through central density depletion. We employ complementary analytic and numerical techniques in order to study equilibrium density profiles and the collective mode structures of condensate shells hosted by a range of trapping potentials. We identify concrete and robust signatures of the evolution from filled to hollow structures and the effects of the emergence of an inner boundary, inclusive of a dip in breathing-mode-type collective mode frequencies and a restructuring of surface mode structure across the transition. By extending our analysis to a two-dimensional transition of a disk to a ring, we show that the collective mode signatures are an essential feature of hollowing, independent of the specific geometry. Finally, we relate our work to past and ongoing experimental efforts and consider the influence of gravity on thin condensate shells. We identify the conditions under which gravitational sag is highly destructive and study the mode-mixing effects of microgravity on the collective modes of these shells.

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