Observation of a discrete time crystal
Observation of a discrete time crystal
复制标题
DOI：
10.1038/nature21413
复制
发表时间：
2017-03-09
期刊：
影响因子：
64.8
通讯作者：
Monroe, C.
中科院分区：
文献类型：
--
作者：
Zhang, J.;Hess, P. W.;Monroe, C.
自发对称性破缺是许多物理学领域的一个基本概念，包括宇宙学、粒子物理学和凝聚态(1)。一个例子是空间平移对称性的破坏，这是晶体形成和从液体到固体的相变的基础。利用晶体在空间中的类比，最近提出了时间平移对称性的破缺和“时间晶体”的出现(2，3)，但后来证明在热平衡中是被禁止的(4-6)。然而，受周期驱动的非平衡Floquet系统可以在一个突然出现的亚谐频率(7-10)表现出持久的时间关联。这种新的物质相被称为“离散时间晶体”(10)。在这里，我们提出了一个离散的时间晶体的实验观测，在一个相互作用的自旋链捕获的原子离子。我们将周期哈密顿量应用于多体定域条件下的系统，并观察到对外部扰动具有鲁棒性的亚谐时间响应。这种时间晶体的观察为研究具有长程时空关联的系统和在本质上非平衡条件下出现的新的物质相打开了大门(7)。
Spontaneous symmetry breaking is a fundamental concept in many areas of physics, including cosmology, particle physics and condensed matter(1). An example is the breaking of spatial translational symmetry, which underlies the formation of crystals and the phase transition from liquid to solid. Using the analogy of crystals in space, the breaking of translational symmetry in time and the emergence of a 'time crystal' was recently proposed(2,3), but was later shown to be forbidden in thermal equilibrium(4-6). However, non-equilibrium Floquet systems, which are subject to a periodic drive, can exhibit persistent time correlations at an emergent subharmonic frequency(7-10). This new phase of matter has been dubbed a 'discrete time crystal'(10). Here we present the experimental observation of a discrete time crystal, in an interacting spin chain of trapped atomic ions. We apply a periodic Hamiltonian to the system under many-body localization conditions, and observe a subharmonic temporal response that is robust to external perturbations. The observation of such a time crystal opens the door to the study of systems with long-range spatio-temporal correlations and novel phases of matter that emerge under intrinsically nonequilibrium conditions(7).