We study the dynamics of torque driven spherical spinners settled on a surface, and demonstrate that hydrodynamic interactions at finite Reynolds numbers can lead to a concentration dependent and nonuniform crystallization. At semidilute concentrations, we observe a rapid formation of a uniform hexagonal structure in the spinner monolayer. We attribute this to repulsive hydrodynamic interactions created by the secondary flow of the spinning particles. Increasing the surface coverage leads to a state with two coexisting spinner densities. The uniform hexagonal structure deviates into a high density crystalline structure surrounded by a continuous lower density hexatically ordered state. We show that this phase separation occurs due to a nonmonotonic hydrodynamic repulsion, arising from a concentration dependent spinning frequency.

中文翻译：

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惯性旋转器地毯中的两相结晶

我们研究了沉积在表面上的扭矩驱动球形旋转器的动力学，并证明了在有限的雷诺数下的流体动力学相互作用会导致浓度依赖性和非均匀结晶。在半稀释浓度下，我们观察到在旋转器单层中快速形成均匀的六角形结构。我们将其归因于纺丝粒子的二次流动所产生的排斥性流体动力相互作用。增加表面覆盖率会导致具有两个同时存在的旋转器密度的状态。均匀的六边形结构偏离为高密度的晶体结构，周围是连续的低密度六方有序状态。我们表明，这种相分离是由于非单调流体动力排斥引起的，它是由浓度依赖性纺丝频率引起的。