Dense assemblies of self-propelled particles that can form solid-like states also known as active or living glasses are abundant around us, covering a broad range of length scales and timescales: from the cytoplasm to tissues, from bacterial biofilms to vehicular traffic jams, and from Janus colloids to animal herds. Being structurally disordered as well as strongly out of equilibrium, these systems show fascinating dynamical and mechanical properties. Using extensive molecular dynamics simulation and a number of distinct dynamical and mechanical order parameters, we differentiate three dynamical steady states in a sheared model active glassy system: 1) a disordered state, 2) a propulsion-induced ordered state, and 3) a shear-induced ordered state. We supplement these observations with an analytical theory based on an effective single-particle Fokker–Planck description to rationalize the existence of the shear-induced orientational ordering behavior in an active glassy system without explicit aligning interactions of, for example, Vicsek type. This ordering phenomenon occurs in the large persistence time limit and is made possible only by the applied steady shear. Using a Fokker–Planck description with parameters that can be measured independently, we make testable predictions for the joint distribution of single-particle position and orientation. These predictions match well with the joint distribution measured from direct numerical simulation. Our results are of relevance for experiments exploring the rheological response of dense active colloids and jammed active granular matter systems.

可以形成类固体状态的自驱动粒子的致密组件，也称为活性玻璃或活玻璃，在我们周围非常丰富，涵盖了广泛的长度尺度和时间尺度：从细胞质到组织，从细菌生物膜到交通堵塞，从 Janus 胶体到动物群。由于结构无序且严重失衡，这些系统表现出令人着迷的动力学和机械特性。使用广泛的分子动力学模拟和许多不同的动力学和机械有序参数，我们区分了剪切模型活性玻璃系统中的三种动态稳态：1）无序状态，2）推进引起的有序状态，3）剪切-诱导有序状态。我们用基于有效的单粒子福克-普朗克描述的分析理论补充了这些观察结果，以合理化活性玻璃系统中剪切诱导的取向有序行为的存在，而无需明确的维切克型对准相互作用。这种有序现象发生在较长的持续时间限制内，并且只有通过施加稳定的剪切才可能实现。使用具有可独立测量的参数的福克-普朗克描述，我们对单粒子位置和方向的联合分布进行可测试的预测。这些预测与直接数值模拟测量的联合分布非常吻合。我们的结果与探索致密活性胶体和堵塞的活性颗粒物质系统的流变响应的实验相关。