Pfeifer Jens C, Bischoff Tobias, Ehlers Georg, Eckhardt Bruno
Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany.
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, 91125,USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Dec;92(6):062208. doi: 10.1103/PhysRevE.92.062208. Epub 2015 Dec 28.
Motivated by experiments on sheared suspensions that show a transition between ordered and disordered phases, we here study the long-time behavior of a sheared and overdamped two-dimensional system of particles interacting by repulsive forces. As a function of interaction strength and shear rate we find transitions between phases with vanishing and large single-particle diffusion. In the phases with vanishing single-particle diffusion, the system evolves towards regular lattices, usually on very slow time scales. Different lattices can be approached, depending on interaction strength and forcing amplitude. The disordered state appears in parameter regions where the regular lattices are unstable. Correlation functions between the particles reveal the formation of shear bands. In contrast to single-particle densities, the spatially resolved two-particle correlation functions vary with time and allow to determine the phase within a period. As in the case of the suspensions, motion in the state with low diffusivity is essentially reversible, whereas in the state with strong diffusion it is not.
受剪切悬浮液实验的启发，这些实验表明了有序相和无序相之间的转变，我们在此研究一个由排斥力相互作用的二维剪切过阻尼粒子系统的长期行为。作为相互作用强度和剪切速率的函数，我们发现了单粒子扩散消失和扩散较大的相之间的转变。在单粒子扩散消失的相中，系统通常在非常缓慢的时间尺度上朝着规则晶格演化。根据相互作用强度和强迫振幅，可以接近不同的晶格。无序状态出现在规则晶格不稳定的参数区域。粒子之间的关联函数揭示了剪切带的形成。与单粒子密度不同，空间分辨的两粒子关联函数随时间变化，并允许在一个周期内确定相。与悬浮液的情况一样，低扩散率状态下的运动基本上是可逆的，而在强扩散状态下则不是。
