Institute for Theoretical Physics, Georg-August-Universität Göttingen, 37077 Göttingen, Germany.
Department of Mathematics, King's College London, London WC2R 2LS, United Kingdom.
Phys Rev Lett. 2020 Nov 20;125(21):218001. doi: 10.1103/PhysRevLett.125.218001.
Recent experiments and simulations have revealed glassy features in, e.g., cytoplasm, living tissues and dense assemblies of self-propelled colloids. This leads to a fundamental question: how do these nonequilibrium (active) amorphous materials differ from conventional passive glasses, created by lowering temperature or increasing density? To address this we investigate the aging after a quench to an almost arrested state of a model active glass former, a Kob-Andersen glass in two dimensions. Each constituent particle is driven by a constant propulsion force whose direction diffuses over time. Using extensive molecular dynamics simulations we reveal rich aging behavior of this dense active matter system: short persistence times of the active forcing give effective thermal aging; in the opposite limit we find a two-step aging process with active athermal aging at short times and activity-driven aging at late times. We develop a dedicated simulation method that gives access to this longtime scaling regime for highly persistent active forces.
最近的实验和模拟揭示了玻璃态特征，例如细胞质、活组织和自推进胶体的密集组装体。这就提出了一个基本问题：这些非平衡（活性）无定形材料与通过降低温度或增加密度产生的传统无源玻璃有何不同？为了解决这个问题，我们研究了模型活性玻璃前体（二维的 Kob-Andersen 玻璃）淬火到几乎停止状态后的老化过程。每个组成粒子都受到常推力的驱动，其方向随时间扩散。我们利用广泛的分子动力学模拟揭示了这种密集的活性物质系统的丰富老化行为：活性力的短持续时间会导致有效热老化；在相反的极限下，我们发现了一个具有两步老化过程的情况，即短时间内的无热老化和长时间内的活性老化。我们开发了一种专用的模拟方法，可以访问这种长时间标度的高持续活性力。
