Physics Department and James Franck Institute, The University of Chicago, Chicago, IL 60605.
Proc Natl Acad Sci U S A. 2013 Sep 24;110(39):15544-8. doi: 10.1073/pnas.1300787110. Epub 2013 Sep 5.
Dislocations, disclinations, and grain boundaries are topological excitations of crystals that play a key role in determining out-of-equilibrium material properties. In this article we study the kinetics, creation, and annihilation processes of these defects in a controllable way by applying "topological tweezers," an array of weak optical tweezers which strain the lattice by weakly pulling on a collection of particles without grabbing them individually. We use topological tweezers to deterministically control individual dislocations and grain boundaries, and reversibly create and destroy dislocation pairs in a 2D crystal of charged colloids. Starting from a perfect lattice, we exert a torque on a finite region and follow the complete step-by-step creation of a disoriented grain, from the creation of dislocation pairs through their reactions to form a grain boundary and their reduction of elastic energy. However, when the grain is rotated back to its original orientation the dislocation reactions do not retrace. Rather, the process is irreversible; the grain boundary expands instead of collapsing.
位错、位错和晶界是晶体的拓扑激发，它们在决定非平衡材料性质方面起着关键作用。在本文中，我们通过应用“拓扑镊子”以可控的方式研究了这些缺陷的动力学、产生和湮灭过程，拓扑镊子是由一系列弱光镊子组成的阵列，通过在不单独抓取它们的情况下对一组粒子进行弱拉力来使晶格变形。我们使用拓扑镊子来确定性地控制单个位错和晶界，并在带电胶体的二维晶体中可逆地创建和破坏位错对。从完美的晶格开始，我们对有限区域施加扭矩，并通过对离散的晶格位错的逐步生成来追踪取向无序晶粒的完整形成过程，从位错对的产生到它们的反应形成晶界以及弹性能量的降低。然而，当晶粒被旋转回原来的取向时，位错反应不会倒转。相反，这个过程是不可逆的；晶界扩张而不是收缩。
