Gerloff Sascha, Klapp Sabine H L
Institut für Theoretische Physik, Hardenbergstrasse 36, Technische Universität Berlin, D-10623 Berlin, Germany.
Phys Rev E. 2016 Dec;94(6-1):062605. doi: 10.1103/PhysRevE.94.062605. Epub 2016 Dec 13.
Using Brownian dynamics (BD) simulations and an analytical approach we investigate the shear-induced, nonequilibrium dynamics of dense colloidal suspensions confined to a narrow slit-pore. Focusing on situations where the colloids arrange in well-defined layers with solidlike in-plane structure, the confined films display complex, nonlinear behavior such as collective depinning and local transport via density excitations. These phenomena are reminiscent of colloidal monolayers driven over a periodic substrate potential. In order to deepen this connection, we present an effective model that maps the dynamics of the shear-driven colloidal layers to the motion of a single particle driven over an effective substrate potential. This model allows us to estimate the critical shear rate of the depinning transition based on the equilibrium configuration, revealing the impact of important parameters, such as the slit-pore width and the interaction strength. We then turn to heterogeneous systems where a layer of small colloids is sheared with respect to bottom layers of large particles. For these incommensurate systems we find that the particle transport is dominated by density excitations resembling the so-called "kink" solutions of the Frenkel-Kontorova (FK) model. In contrast to the FK model, however, the corresponding "antikinks" do not move.
我们使用布朗动力学（BD）模拟和一种解析方法，研究了限制在狭窄狭缝孔中的稠密胶体悬浮液的剪切诱导非平衡动力学。聚焦于胶体以具有类固体平面内结构的明确层状排列的情况，受限薄膜表现出复杂的非线性行为，如集体脱钉和通过密度激发的局部输运。这些现象让人联想到在周期性衬底势驱动下的胶体单层。为了深化这种联系，我们提出了一个有效模型，该模型将剪切驱动的胶体层的动力学映射到在有效衬底势驱动下单个粒子的运动。这个模型使我们能够基于平衡构型估计脱钉转变的临界剪切速率，揭示重要参数的影响，如狭缝孔宽度和相互作用强度。然后我们转向非均匀系统，其中一层小胶体相对于大颗粒的底层被剪切。对于这些不匹配的系统，我们发现粒子输运由类似于弗伦克尔 - 康托罗娃（FK）模型所谓“扭结”解的密度激发主导。然而，与FK模型不同的是，相应的“反扭结”并不移动。
