Pertsinidis A, Ling X S
Department of Physics, Brown University, Providence, Rhode Island 02912, USA.
Nature. 2001 Sep 13;413(6852):147-50. doi: 10.1038/35093077.
Uniform colloidal microspheres dispersed in a solvent will, under appropriate conditions, self-assemble into ordered crystalline structures. Using these colloidal crystals as a model system, a great variety of problems of interest to materials science, physical chemistry, and condensed-matter physics have been investigated during the past two decades. Recently, it has been demonstrated that point defects can be created in two-dimensional colloidal crystals by manipulating individual particles with optical tweezers. Direct imaging of these defects verified that their stable configurations have lower symmetry than the underlying triangular lattice, as predicted by numerical simulations for a number of two-dimensional systems. It was also observed that point defects can dissociate into pairs of well-separated dislocations, a topological excitation especially important in two dimensions. Here we use a similar experimental system to study the dynamics of mono- and di-vacancies in two-dimensional colloidal crystals. We see evidence that the excitation of point defects into dislocation pairs enhances the diffusion of di-vacancies. Moreover, the hopping of the defects does not follow a pure random walk, but exhibits surprising memory effects. We expect the results presented in this work to be relevant for explaining the dynamics of other two-dimensional systems.
分散在溶剂中的均匀胶体微球在适当条件下会自组装成有序的晶体结构。在过去二十年中，以这些胶体晶体为模型系统，研究了材料科学、物理化学和凝聚态物理等领域中各种各样感兴趣的问题。最近，有研究表明，通过用光学镊子操纵单个粒子，可以在二维胶体晶体中产生点缺陷。对这些缺陷的直接成像证实，正如许多二维系统的数值模拟所预测的那样，它们的稳定构型比底层的三角晶格具有更低的对称性。还观察到点缺陷可以解离成一对分离良好的位错，这是一种在二维中特别重要的拓扑激发。在这里，我们使用类似的实验系统来研究二维胶体晶体中单空位和双空位的动力学。我们发现有证据表明，点缺陷激发到位错对会增强双空位的扩散。此外，缺陷的跳跃并不遵循纯粹的随机游走，而是表现出惊人的记忆效应。我们预计本文所呈现的结果与解释其他二维系统的动力学相关。
