Physics Institute, Heidelberg University, Heidelberg, Germany.
Institute for Theoretical Physics, Heidelberg University, Heidelberg, Germany.
Science. 2019 Jul 19;365(6450):268-272. doi: 10.1126/science.aau4402.
Quantum anomalies are violations of classical scaling symmetries caused by divergences that appear in the quantization of certain classical theories. Although they play a prominent role in the quantum field theoretical description of many-body systems, their influence on experimental observables is difficult to discern. In this study, we discovered a distinctive manifestation of a quantum anomaly in the momentum-space dynamics of a two-dimensional (2D) Fermi superfluid of ultracold atoms. The measured pair momentum distributions of the superfluid during a breathing mode cycle exhibit a scaling violation in the strongly interacting regime. We found that the power-law exponents that characterize long-range phase correlations in the system are modified by the quantum anomaly, emphasizing the influence of this effect on the critical properties of 2D superfluids.
量子反常是由某些经典理论的量子化中出现的发散引起的对经典标度对称性的违反。尽管它们在多体系统的量子场理论描述中起着突出的作用，但它们对实验可观察量的影响很难察觉。在这项研究中，我们在二维（2D）超冷原子费米超流的动量空间动力学中发现了量子反常的一个独特表现。在呼吸模式循环中，超流的测量对动量分布表现出在强相互作用区域的标度违反。我们发现，系统中长程相位相关的标度律指数被量子反常所修饰，强调了这种效应对 2D 超流临界性质的影响。
