Wang Yunfei, Li Yuqing, Wu Jizhou, Liu Wenliang, Hu Jiazhong, Ma Jie, Xiao Liantuan, Jia Suotang
Opt Express. 2021 Apr 26;29(9):13960-13967. doi: 10.1364/OE.419854.
The Bose-Einstein condensation (BEC) of Cs atoms offers an appealing platform for studying the many-body physics of interacting Bose quantum gases, owing to the rich Feshbach resonances that can be readily achieved in the low magnetic field region. However, it is notoriously difficult to cool Cs atoms to their quantum degeneracy. Here we report a hybrid evaporative cooling of Cs atoms to BEC. Our approach relies on a combination of the magnetically tunable evaporation with the optical evaporation of atoms in a magnetically levitated optical dipole trap overlapping with a dimple trap. The magnetic field gradient is reduced for the magnetically tunable evaporation. The subsequent optical evaporation is performed by lowering the depth of the dimple trap. We study the dependence of the peak phase space density (PSD) and temperature on the number of atoms during the evaporation process, as well as how the PSD and atom number vary with the trap depth. The results are in excellent agreement with the equation model for evaporative cooling.
由于在低磁场区域能够很容易地实现丰富的费什巴赫共振，铯原子的玻色 - 爱因斯坦凝聚（BEC）为研究相互作用的玻色量子气体的多体物理提供了一个有吸引力的平台。然而，将铯原子冷却到量子简并态是出了名的困难。在此，我们报告了一种将铯原子混合蒸发冷却至玻色 - 爱因斯坦凝聚的方法。我们的方法依赖于磁可调蒸发与处于磁悬浮光偶极阱中且与酒窝阱重叠的原子的光蒸发相结合。对于磁可调蒸发，磁场梯度会降低。随后通过降低酒窝阱的深度来进行光蒸发。我们研究了蒸发过程中峰值相空间密度（PSD）和温度对原子数的依赖性，以及PSD和原子数如何随阱深度变化。结果与蒸发冷却的方程模型高度吻合。
