Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Phys Rev Lett. 2011 Nov 4;107(19):190403. doi: 10.1103/PhysRevLett.107.190403. Epub 2011 Nov 2.
We study the condensed fraction of a harmonically trapped atomic Bose gas at the critical point predicted by mean-field theory. The nonzero condensed fraction f(0) is induced by critical correlations which increase the transition temperature T(c) above T(c) (MF). Unlike the T(c) shift in a trapped gas, f(0) is sensitive only to the critical behavior in the quasiuniform part of the cloud near the trap center. To leading order in the interaction parameter a/λ(0), where a is the s-wave scattering length and λ(0) the thermal wavelength, we expect a universal scaling f(0) proportionally (a/λ(0))(4). We experimentally verify this scaling using a Feshbach resonance to tune a/λ(0). Further, using the local density approximation, we compare our measurements with the universal result obtained from Monte Carlo simulations for a uniform system, and find excellent quantitative agreement.
我们研究了在平均场理论预测的临界点下被谐波阱束缚的原子玻色气体的凝聚分数。非零凝聚分数 f(0) 是由临界相关引起的，这会使转变温度 T(c) 高于 T(c)(MF)。与被困气体中的 T(c) 偏移不同，f(0) 仅对云中心附近准均匀部分的临界行为敏感。在相互作用参数 a/λ(0) 的主导阶数中，其中 a 是 s 波散射长度，λ(0) 是热波长，我们预计会有一个普遍的标度，f(0) 与 (a/λ(0))(4) 成比例。我们使用费希巴赫共振来调整 a/λ(0)，从而实验验证了这种标度。此外，我们使用局域密度近似，将我们的测量结果与均匀系统的蒙特卡罗模拟获得的通用结果进行比较，并发现非常好的定量一致性。
