Zou Y-Q, Bakkali-Hassani B, Maury C, Le Cerf É, Nascimbene S, Dalibard J, Beugnon J
Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL Research University, Sorbonne Université, 11 Place Marcelin Berthelot, 75005, Paris, France.
Nat Commun. 2021 Feb 3;12(1):760. doi: 10.1038/s41467-020-20647-6.
Tan's contact is a quantity that unifies many different properties of a low-temperature gas with short-range interactions, from its momentum distribution to its spatial two-body correlation function. Here, we use a Ramsey interferometric method to realize experimentally the thermodynamic definition of the two-body contact, i.e., the change of the internal energy in a small modification of the scattering length. Our measurements are performed on a uniform two-dimensional Bose gas of Rb atoms across the Berezinskii-Kosterlitz-Thouless superfluid transition. They connect well to the theoretical predictions in the limiting cases of a strongly degenerate fluid and of a normal gas. They also provide the variation of this key quantity in the critical region, where further theoretical efforts are needed to account for our findings.
谭接触是一个将具有短程相互作用的低温气体的许多不同性质统一起来的量，从其动量分布到其空间两体关联函数。在这里，我们使用拉姆齐干涉测量方法通过实验实现两体接触的热力学定义，即散射长度的微小改变中内能的变化。我们的测量是在跨越贝雷津斯基 - 科斯特利茨 - Thouless超流转变的均匀二维铷原子玻色气体上进行的。它们在强简并流体和正常气体的极限情况下与理论预测吻合得很好。它们还提供了这个关键量在临界区域的变化情况，在该区域需要进一步的理论研究来解释我们的发现。
