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arXiv 2106.00835cond-mat.quant-gas
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膨胀壳状玻色-爱因斯坦凝聚体的热力学

Thermodynamics in expanding shell-shaped Bose-Einstein condensates

Brendan Rhyno, Nathan Lundblad, David C. Aveline, Courtney Lannert, Smitha Vishveshwara

备注：
18 pages, 9 figures
发表信息：
Phys. Rev. A 104, 063310 (2021)
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摘要：

受国际空间站冷原子实验室（CAL）产生的玻色-爱因斯坦凝聚体（BEC）研究的启发，我们对壳状BEC的热力学性质进行了研究。在球对称的“气泡陷阱”的潜力的背景下，我们研究了系统的演变，从小填充球中空，大，薄壳通过调整陷阱参数。我们分析了气泡陷阱的光谱和状态，并跟踪整个演化过程中径向和角向模式之间的光谱的明显变化。激发光谱的这种分离提供了在给定温度下将维度交叉量化到准2D物理的基础。使用光谱数据，对于一系列的陷阱参数，我们计算的临界温度为一个固定数量的粒子形成BEC。对于一组初始温度，我们还评估了温度的变化，将发生在绝热膨胀从小填充球到大薄壳的陷阱进行动态调整。我们表明，该系统在此膨胀过程中冷却，但临界温度的下降发生得更快，从而导致任何初始冷凝物的耗尽。我们对比我们的光谱方法与标准的半经典处理，我们发现必须谨慎使用的薄壳极限。关于相互作用，使用充满活力的考虑和Bogoliubov治疗证实，我们证明，他们将是不太重要的薄壳，由于密度降低，但涡物理将成为更占主导地位。最后，我们将我们的治疗方法应用于实际模拟CAL实验的陷阱，并借用绝热膨胀过程中理想化气泡情况下的热力学见解。

英文摘要：

Inspired by investigations of Bose-Einstein condensates (BECs) produced in the Cold Atom Laboratory (CAL) aboard the International Space Station, we present a study of thermodynamic properties of shell-shaped BECs. Within the context of a spherically symmetric `bubble trap' potential, we study the evolution of the system from small filled spheres to hollow, large, thin shells via the tuning of trap parameters. We analyze the bubble trap spectrum and states, and track the distinct changes in spectra between radial and angular modes across the evolution. This separation of the excitation spectrum provides a basis for quantifying dimensional cross-over to quasi-2D physics at a given temperature. Using the spectral data, for a range of trap parameters, we compute the critical temperature for a fixed number of particles to form a BEC. For a set of initial temperatures, we also evaluate the change in temperature that would occur in adiabatic expansion from small filled sphere to large thin shell were the trap to be dynamically tuned. We show that the system cools during this expansion but that the decrease in critical temperature occurs more rapidly, thus resulting in depletion of any initial condensate. We contrast our spectral methods with standard semiclassical treatments, which we find must be used with caution in the thin-shell limit. With regards to interactions, using energetic considerations and corroborated through Bogoliubov treatments, we demonstrate that they would be less important for thin shells due to reduced density but vortex physics would become more predominant. Finally, we apply our treatments to traps that realistically model CAL experiments and borrow from the thermodynamic insights found in the idealized bubble case during adiabatic expansion.

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