近日，清华大学的尤力及其研究小组与奥地利维也纳工业大学的Thomas Pohl等人合作并取得一项新进展。经过不懈努力，他们对强相互作用里德伯气体中的耗散时间晶体进行研究。相关研究成果已于2024年7月2日在国际知名学术期刊《自然—物理学》上发表。

据悉，自发对称性破缺的概念已经很好地建立，以表征物质的经典和量子相变，如凝聚，结晶或量子磁性。将这种范式推广到时间维度可以导致时间晶体相，它自发地打破了系统的时间平移对称性。虽然连续时间晶体在平衡状态下的存在性一直受到不可行定理的挑战，但这一困难可以通过开放系统中的耗散来克服。

该研究团队报道了在室温原子气体中对这种耗散时间晶体有序的实验观察，其中基态原子连续地被驱动到里德伯态。研究人员通过光子传输的持续振荡揭示了涌现时间晶体，并证明了所观察到的极限环是由不同里德伯分量之间的共存和竞争产生的。振荡的非衰减自相关特性和对时间噪声的鲁棒性表明了真正长程时间有序的建立，证明了连续时间晶体的实现。

附：英文原文

Title: Dissipative time crystal in a strongly interacting Rydberg gas

Author: Wu, Xiaoling, Wang, Zhuqing, Yang, Fan, Gao, Ruochen, Liang, Chao, Tey, Meng Khoon, Li, Xiangliang, Pohl, Thomas, You, Li

Issue&Volume: 2024-07-02

Abstract: The notion of spontaneous symmetry breaking has been well established to characterize classical and quantum phase transitions of matter, such as condensation, crystallization or quantum magnetism. Generalizations of this paradigm to the time dimension can lead to a time crystal phase, which spontaneously breaks the time-translation symmetry of the system. Although the existence of a continuous time crystal at equilibrium has been challenged by no-go theorems, this difficulty can be circumvented by dissipation in an open system. Here we report the experimental observation of such a dissipative time-crystalline order in a room-temperature atomic gas, where ground-state atoms are continuously driven to Rydberg states. The emergent time crystal is revealed by persistent oscillations of the photon transmission, and we show that the observed limit cycles arise from the coexistence and competition between distinct Rydberg components. The non-decaying autocorrelation of the oscillation, together with the robustness against temporal noises, indicates the establishment of true long-range temporal order and demonstrates the realization of a continuous time crystal.

DOI: 10.1038/s41567-024-02542-9

Source: https://www.nature.com/articles/s41567-024-02542-9