Sun Jian, Niu Jiasen, Li Yifan, Liu Yang, Pfeiffer L N, West K W, Wang Pengjie, Lin Xi
International Center for Quantum Materials, Peking University, Beijing 100871, China.
Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA.
Fundam Res. 2021 Aug 8;2(2):178-183. doi: 10.1016/j.fmre.2021.07.006. eCollection 2022 Mar.
The phenomenon of group motion is common in nature, ranging from the schools of fish, birds and insects, to avalanches, landslides and sand drift. If we treat objects as collectively moving particles, such phenomena can be studied from a physical point of view, and the research on many-body systems has proved that marvelous effects can arise from the simplest individuals. The motion of numerous individuals presents different dynamic phases related to the ordering of the system. However, it is usually difficult to study the dynamic ordering and its transitions through experiments. Electron bubble states formed in a two-dimensional electron gas, as a type of electron solids, can be driven by an external electric field and provide a platform to study the dynamic collective behaviors. Here, we demonstrate that the noise spectrum is a powerful method to investigate the dynamics of bubble states. We observed not only the phenomena of dynamically ordered and disordered structures, but also unexpected alternations between them. Our results show that a dissipative system can convert between chaotic structures and ordered structures when tuning global parameters, which is concealed in conventional transport measurements of resistance or conductance. Moreover, charging the objects to study the electrical noise spectrum in collective motions can be an additional approach to revealing dynamic ordering transitions.
群体运动现象在自然界中很常见，从鱼群、鸟群和昆虫群，到雪崩、山体滑坡和沙流。如果我们将物体视为集体运动的粒子，那么这种现象就可以从物理学角度进行研究，而对多体系统的研究已经证明，最简单的个体也能产生奇妙的效果。众多个体的运动呈现出与系统有序性相关的不同动态相。然而，通过实验研究动态有序性及其转变通常很困难。在二维电子气中形成的电子泡态作为一种电子固体，可以由外部电场驱动，并为研究动态集体行为提供一个平台。在这里，我们证明噪声谱是研究泡态动力学的一种有力方法。我们不仅观察到了动态有序和无序结构的现象，还观察到了它们之间意想不到的交替。我们的结果表明，一个耗散系统在调整全局参数时可以在混沌结构和有序结构之间转换，这在传统的电阻或电导输运测量中是隐藏的。此外，对物体充电以研究集体运动中的电噪声谱可能是揭示动态有序转变的另一种方法。
