无序介质中弹道活性物质系统的堵塞与脱钉
Clogging and Depinning of Ballistic Active Matter Systems in Disordered Media
摘要：
我们数值研究弹道主动磁盘驱动通过随机障碍阵列。钉扎或堵塞状态的形成发生在主动盘的障碍物密度比被动盘低得多。作为障碍物密度的函数，我们确定了几个不同的阶段，包括一个depinned波动的集群状态，一个固定的单集群或堵塞状态，一个固定的多集群状态，一个固定的凝胶状态，和一个固定的无序状态。在较低的有效磁盘密度，漂移均匀的液体形成的障碍物的情况下，但当即使是少量的障碍物被引入，磁盘组织成钉扎相分离的集群状态，其中集群成核周围的障碍物，类似于润湿现象。我们研究了如何退钉阈值的变化作为磁盘或障碍物密度的函数，并找到一个交叉从集体钉扎集群状态到无序的塑料退钉过渡作为增加障碍物密度的函数。我们将此与非弹道活性粒子的行为进行比较，结果表明，当我们将活性从完全被动改变为完全弹道时，阻塞的相分离状态出现在主动和被动限制中，而对于中间活性，出现容易流动的液体状态，并且存在最佳活性水平，使通过样品的通量最大化。
英文摘要：
We numerically examine ballistic active disks driven through a random obstacle array. Formation of a pinned or clogged state occurs at much lower obstacle densities for the active disks than for passive disks. As a function of obstacle density we identify several distinct phases including a depinned fluctuating cluster state, a pinned single cluster or jammed state, a pinned multicluster state, a pinned gel state, and a pinned disordered state. At lower active disk densities, a drifting uniform liquid forms in the absence of obstacles, but when even a small number of obstacles are introduced, the disks organize into a pinned phase-separated cluster state in which clusters nucleate around the obstacles, similar to a wetting phenomenon. We examine how the depinning threshold changes as a function of disk or obstacle density, and find a crossover from a collectively pinned cluster state to a disordered plastic depinning transition as a function of increasing obstacle density. We compare this to the behavior of nonballistic active particles and show that as we vary the activity from completely passive to completely ballistic, a clogged phase-separated state appears in both the active and passive limits, while for intermediate activity, a readily flowing liquid state appears and there is an optimal activity level that maximizes the flux through the sample.
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