Tononi A, Cinti F, Salasnich L
Dipartimento di Fisica e Astronomia "Galileo Galilei," Università di Padova, via Marzolo 8, Padova 35131, Italy.
Dipartimento di Fisica e Astronomia, Università di Firenze, I-50019 Sesto Fiorentino (FI), Italy.
Phys Rev Lett. 2020 Jul 3;125(1):010402. doi: 10.1103/PhysRevLett.125.010402.
The recent developments of microgravity experiments with ultracold atoms have produced a relevant boost in the study of shell-shaped ellipsoidal Bose-Einstein condensates. For realistic bubble-trap parameters, here we calculate the critical temperature of Bose-Einstein condensation, which, if compared to the one of the bare harmonic trap with the same frequencies, shows a strong reduction. We simulate the zero-temperature density distribution with the Gross-Pitaevskii equation, and we study the free expansion of the hollow condensate. While part of the atoms expands in the outward direction, the condensate self-interferes inside the bubble trap, filling the hole in experimentally observable times. For a mesoscopic number of particles in a strongly interacting regime, for which more refined approaches are needed, we employ quantum Monte Carlo simulations, proving that the nontrivial topology of a thin shell allows superfluidity. Our work constitutes a reliable benchmark for the forthcoming scientific investigations with bubble traps.
超冷原子微重力实验的最新进展极大地推动了壳状椭球玻色-爱因斯坦凝聚体的研究。对于实际的气泡陷阱参数，我们在此计算玻色-爱因斯坦凝聚的临界温度，与具有相同频率的裸简谐振子陷阱相比，该临界温度显著降低。我们用格罗斯-皮塔耶夫斯基方程模拟零温度密度分布，并研究中空凝聚体的自由膨胀。当部分原子向外膨胀时，凝聚体在气泡陷阱内部发生自干涉，在实验可观测的时间内填补空洞。对于处于强相互作用 regime 且需要更精细方法的介观粒子数，我们采用量子蒙特卡罗模拟，证明薄壳的非平凡拓扑结构允许超流性。我们的工作为即将开展的气泡陷阱科学研究提供了可靠的基准。
