Ross J A, Deuar P, Shin D K, Thomas K F, Henson B M, Hodgman S S, Truscott A G
Research School of Physics, Australian National University, Canberra, 0200, Australia.
Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, 02-688, Warsaw, Poland.
Sci Rep. 2022 Aug 1;12(1):13178. doi: 10.1038/s41598-022-16477-9.
We present observations of the high momentum tail in expanding Bose-Einstein condensates of metastable Helium atoms released from a harmonic trap. The far-field density profile exhibits features that support identification of the tails of the momentum distribution as originating in the in-situ quantum depletion prior to release. Thus, we corroborate recent observations of slowly-decaying tails in the far-field beyond the thermal component. This observation is in conflict with the hydrodynamic theory, which predicts that the in-situ depletion does not survive when atoms are released from a trap. Indeed, the depleted tails even appear stronger in the far-field than expected before release, and we discuss the challenges of interpreting this in terms of the Tan contact in the trapped gas. In complement to these observations, full quantum simulations of the experiment show that, under the right conditions, the depletion can persist into the far field after expansion. Moreover, the simulations provide mechanisms for survival and for the the large-momentum tails to appear stronger after expansion due to an acceleration of the depleted atoms by the mean-field potential. However, while in qualitative agreement, the final depletion observed in the experiment is much larger than in the simulation.
我们展示了从谐波阱中释放的亚稳态氦原子的膨胀玻色-爱因斯坦凝聚体中高动量尾部的观测结果。远场密度分布呈现出的特征支持将动量分布的尾部识别为源于释放前的原位量子耗尽。因此，我们证实了最近在远场中超出热成分的缓慢衰减尾部的观测结果。这一观测结果与流体动力学理论相冲突，该理论预测当原子从阱中释放时，原位耗尽不会留存。实际上，耗尽的尾部在远场中甚至比释放前预期的更强，并且我们讨论了根据捕获气体中的谭接触来解释这一现象的挑战。作为这些观测结果的补充，该实验的全量子模拟表明，在合适的条件下，耗尽在膨胀后可以持续到远场。此外，模拟提供了耗尽持续存在以及由于平均场势对耗尽原子的加速作用，使得大动量尾部在膨胀后显得更强的机制。然而，尽管在定性上一致，但实验中观测到的最终耗尽比模拟中的要大得多。
