Probing Fluctuations and Nanoscale Dynamics in Glasses and Other Complex Materials

在这项研究中，新的扫描探针显微镜（SPM）技术将用于测量有机玻璃、聚合物和其他材料的介电和粘弹性性能随频率、时间、场和位置的波动。对玻璃中纳米尺度波动的直接研究可以提供导致非指数弛豫、发散弛豫时间和玻璃化转变标度的动力学过程的详细图像。这些研究将解决关键问题，如分子协同性的长度尺度和性质，以及异质性及其时间演化的重要性。表征玻璃协同性的统计度量可以直接与模拟提供的统计度量进行比较。介质涨落也将用于研究宏观老化玻璃中涨落耗散定理（FDT）的预测违反。虽然在实验中从未观察到，但这些非平衡FDT违反可能提供了一种探测平衡玻璃序参数的手段，并且是强烈依赖于模型的。这些研究解决了非平衡统计力学中一个尚未解决的基本问题，并测试了各种玻璃化转变模型。研究生和博士后参与这些调查。这项研究涉及液体和聚合物如何冻结成无序固体，即玻璃的基本问题。虽然过去在这些问题上已经做了很多工作，但目前使用扫描探针显微镜的技术现在允许在近原子/分子水平上进行这些研究。在这种方式下，人们发现复杂材料的物理性质在近分子长度尺度上可以发生巨大变化。这项研究站在当代凝聚态物理领域的前沿，并有望对我们对复杂材料行为的理解以及未来技术做出重大贡献。本研究为凝聚态物理和材料科学这一新兴领域的研究生和博士后研究人员的培养提供了极好的机会，从而为21世纪的物理学家和材料科学家的专业骨干的创建做出了贡献。＊＊＊

9877069IsraeloffIn this research novel scanning probe microscopy (SPM) techniques will be used to measure the fluctuations in the dielectric and visco-elastic properties of organic glasses, polymers, and other materials as a function of frequency, time, field and position. The direct study of nano-scale fluctuations in glasses could provide a detailed picture of the dynamical processes leading to non-exponential relaxation, diverging relaxation times, and scaling at the glass transition. These investigations will address critical issues such as the length scale and nature of the molecular cooperativity, and the importance of heterogeneity and its time evolution. Statistical measures which characterize glassy cooperativity can be directly compared with those provided by simulations. Dielectric fluctuations will also be used to investigate predicted violations of the fluctuation-dissipation theorem (FDT) in macroscopic aging glasses. Although never observed in experiments, these non-equilibrium FDT violations may provide a means to probe the equilibrium glass order parameter, and are strongly model dependent. These researches address a fundamental unresolved issue in non-equilibrium statistical mechanics as well as test various glass transition models. Graduate students and postdocs participate in these investigations.%%% This research deals with fundamental problems of how liquids and polymers freeze into disordered solids, i.e., glasses. Though much work in the past has been done on these problems, present technology employing scanning probe microscopy now allow such studies to be performed on a near-atomic/molecular level. In this manner it was found that the physical properties of complex materials can vary dramatically when probed at near molecular length scales. This research stands at the forefront of one of the areas of contemporary condensed matter physics and is expected to make significant contributions to our understanding on the behavior of complex materials and thus to future technology. This research provides excellent opportunities for the training of graduate students and post doctoral research associates in an emerging area of condensed matter physics and materials science, and thereby contributes to the creation of an expert cadre of physicists and materials scientists for employment in the 21st Century. ***