Swimmers and self-propelled particles are physical models for the collective behavior and motility of a wide variety of living systems, such as bacteria colonies, bird flocks, and fish schools. Such artificial active materials are amenable to physical models which reveal the microscopic mechanisms underlying the collective behavior. Here we study colloids in a dc electric field. Our quasi-two-dimensional system of electrically driven particles exhibits a rich and exotic phase behavior exhibiting passive crystallites, motile crystallites, an active gas, and banding. Amongst these are two mesophases, reminiscent of systems with competing interactions. At low field strengths activity suppresses demixing, leading to motile crystallites. Meanwhile, at high field strengths, activity drives partial demixing to traveling bands. We parametrize a particulate simulation model which reproduces the experimentally observed phases.

中文翻译：

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竞争的主动和被动相互作用驱动了类胶体晶体和活性胶体中的有序带

游泳者和自我推进的颗粒是各种生物系统（例如细菌群落，鸟群和鱼群）的集体行为和运动的物理模型。这种人造活性材料适合于揭示集体行为基础的微观机理的物理模型。在这里，我们研究直流电场中的胶体。我们的电驱动粒子的准二维系统表现出丰富而奇特的相态，表现出无源微晶，能动微晶，活性气体和谱带。其中有两个中间阶段，让人联想到具有竞争性相互作用的系统。在低场强下，活性抑制了混合现象，从而导致了微晶运动。同时，在高场强下，活动驱动部分分解为行进频段。我们参数化一个颗粒模拟模型，该模型可再现实验观察到的相。