The James Franck Institute, The University of Chicago, Chicago, IL 60637, USA.
Science. 2012 Mar 2;335(6072):1070-2. doi: 10.1126/science.1217990. Epub 2012 Feb 16.
Quantum criticality emerges when a many-body system is in the proximity of a continuous phase transition that is driven by quantum fluctuations. In the quantum critical regime, exotic, yet universal properties are anticipated; ultracold atoms provide a clean system to test these predictions. We report the observation of quantum criticality with two-dimensional Bose gases in optical lattices. On the basis of in situ density measurements, we observe scaling behavior of the equation of state at low temperatures, locate the quantum critical point, and constrain the critical exponents. We observe a finite critical entropy per particle that carries a weak dependence on the atomic interaction strength. Our experiment provides a prototypical method to study quantum criticality with ultracold atoms.
当一个多体系统接近由量子涨落驱动的连续相变时，就会出现量子临界性。在量子临界区，预计会出现奇异但普遍的性质；超冷原子提供了一个干净的系统来测试这些预测。我们报告了在光学晶格中二维玻色气体的量子临界性的观测结果。基于原位密度测量，我们在低温下观察到状态方程的标度行为，定位量子临界点，并约束临界指数。我们观察到每个粒子的有限临界熵，它与原子相互作用强度的弱依赖关系。我们的实验提供了一种用超冷原子研究量子临界性的典型方法。
