Thermally Activated Dynamics in 2D Colloidal Glasses and Crystals

非技术摘要：在这个项目中，该团队试图揭示许多材料在没有通常的结晶过程的情况下突然从液体变成固体的微观机制(S)。最熟悉的是窗户玻璃。窗户玻璃是缓慢老化的液体还是真正的固体，这在科学界是一个长期悬而未决的问题。在最近对二维(2D)胶体玻璃研究的基础上，该团队计划同时使用实验和理论来研究玻璃化转变的起源(S)。实验和理论活动将互惠互利，为假设提供动力和检验。这项研究的结果可以帮助科学家和工程师设计新材料。例如，了解杂质或颗粒大小变化如何影响玻璃材料稳定性的机制(S)，可能会让科学家人为地设计此类杂质来改善材料的性能，类似于将杂质引入超导体以制造更强大的磁体。这项拟议的研究为两名博士生以及凝聚态物理本科生和硕士生提供了极好的培训。培养下一代美国材料科学科学家，对保持美国在科学技术上的领先地位具有重要意义。技术摘要：该团队计划使用视频显微镜和蒙特卡罗模拟来研究凝聚态物理中的两组相关问题：(1)最近发现的各向异性粒子2D胶体玻璃中的微观机制是什么？(2)2D胶体晶体中沿小角度晶界形成的边缘位错阵列是否经历有限温度相变，以及当宿主2D晶体中有杂质粒子时，相变会发生什么？根本的问题是无序如何影响物质的相态和相变。第一个项目将研究棒的两步2D胶体玻璃化转变的物理机制。拟议的实验将用于区分2D中玻璃化转变的各种相互竞争的场景。第二个项目是研究二维胶体晶体中沿小角度晶界形成的边缘位错阵列中可能出现的一种新的相变，以及无序对相变和动力学的影响。这一结果将对理解凝聚态系统中的缺陷和玻璃态产生重要影响。这项研究的结果可以帮助科学家和工程师设计造福社会的新材料。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical abstract: In this project, the team seeks to uncover the microscopic mechanism(s) by which many materials change suddenly from a liquid to a solid without the usual crystallization process. The most familiar one is the window glass. Whether the window glass is a slowly aging liquid or a true solid is a longstanding unresolved question in science. Building on the recent research in two-dimensional (2D) colloidal glasses, the team plans to use both experiment and theory to study the origin(s) of the glass transition. The experimental and theoretical activities will benefit each other, providing motivation and testing of the hypotheses. The results of this research can benefit scientists and engineers in designing new materials. For example, understanding the mechanism(s) of how impurities or particle size variations impact the stability of the glassy material may allow scientists to artificially engineer such impurities to improve the properties of the materials, similar to introducing impurities into superconductors to make stronger magnets. The proposed research provides excellent training for two Ph.D. students, and undergraduate and master students in condensed matter physics. Training the next generation American scientists in materials science is of great importance in maintaining the US preeminence in science and technology. Technical abstract:The team plans to use video microscopy and Monte Carlo simulations to study two sets of related questions in condensed matter physics: (1) What is the microscopic mechanism in the recently discovered 2D colloidal glasses of anisotropic particles? (2) Does an array of edge dislocations formed along a low-angle grain boundary in a 2D colloidal crystal undergo a finite temperature phase transition and what happens to the phase transition when there are impurity particles in the hosting 2D crystal? The underlying fundamental question is how phases of matter and phase transitions are impacted by disorder. The first project will investigate the physical mechanism of a two-step 2D colloidal glass transition of rods. The proposed experiments will be used to distinguish various competing scenarios of the glass transition in 2D. The second project is to study a possible novel phase transition in an array of edge dislocations formed along a low-angle grain boundary in a 2D colloidal crystal and the effects of disorder on the phase transition and dynamics. The results will have a significant impact on the understanding of defects and the glassy states in condensed matter systems. The results of this research can help scientists and engineers in designing new materials for the benefit of society.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.