Dynamics of Condensed Matter Systems

我的研究集中在微观结构的时间演化。由于微观结构取决于样品的历史，因此需要非平衡态热力学来理解。材料的微观结构对其大多数物理和机械性能至关重要。不仅故障率，但许多其他重要的性能，包括拉伸强度，化学反应性和磁性，取决于这种形态至关重要。这些结构的典型长度尺度是微米。许多先进的材料，通常被称为"现代空间时代“材料，其特性是通过精心和复杂的加工技术控制其微观结构而获得的。理解微观结构如何产生、如何表征它们、它们如何随时间演化以及理想地控制它们是物理学中的一个重要基础问题。无序系统中相干性和相关性的性质和作用仍然没有完全理解。实时原位衍射测量，使用时间分辨衍射或X射线光子相关光谱，允许测量的微观结构的条件下，类似于传统的处理，因此非常适合这些研究。发展的两个主要领域是更好的仪器和技术，用于原位时间分辨散射，以帮助解决这些问题，并更好地理解上述物理使用它们。我的观点是，物理学最大的影响之一是发展了其他科学所使用的仪器。为了实现这一目标，我参与设计和建造仪器，以使用SLAC最亮的X射线同步加速器源和新的X射线激光。最新的项目是一个新的时间分辨飞秒电子衍射装置。这是与B合作的。Siwick和D.库克，都是麦吉尔大学的教师这种强调使我们能够在系统脱离平衡以及接近新的平衡或亚稳态时测量材料。除了继续我目前的研究，一个新的项目是与Siwick教授合作进行超快电子衍射（UED）。第一组材料是电荷密度波系统（NbSe 2、TiSe 2、TaSe 2和TaS 2），其中光学激发耦合到电子和声子动力学。为了研究这些效应，需要能够测量亚皮秒时间尺度的结构

My research concentrates on the time evolution of microstructures. Since the microstructure depends on the history of the sample it requires nonequilibrium thermodynamics for its understanding. The microstructure of a material is central to most of its physical and mechanical properties. Not only failure rates, but many other important properties including tensile strength, chemical reactivity and magnetic coercivity, depend crucially on this morphology. The typical length scales of these structures is micrometers. Many of the advanced materials, often denoted as ``modern space age'' materials, obtain their properties from controlling their microstructure by careful and sophisticated processing techniques. It is an important fundamental problem in physics to understand how microstructures arise, how to characterize them, how they evolve in time and ideally to control them. The nature and role of coherence and correlations in disordered systems is still not fully understood. Real-time in-situ diffraction measurements, using either time resolved diffraction or x-ray photon correlation spectroscopy, allow measurements of the microstructure under conditions similar to conventional processing and therefore are ideally suited for these studies. Two main areas of development are better instrumentation and techniques for in-situ time-resolved scattering to help address these issues and to better understand the physics described above using them. It is my opinion is that one of the largest impacts of physics has been to develop the instrumentation used by the rest of science. In order to pursue this objective, I am involved in designing and building instrumentation to use the brightest x-ray synchrotron sources and the new x-ray laser at SLAC. The newest project is a new time-resolved femtosecond electron diffraction setup. This is in collaboration with B. Siwick and D. Cooke, both faculty at McGill. This emphasis has allowed us to measure materials while the system is being taken out of equilibrium and as it approaches the new equilibrium or metastable state. Besides continuing my current research, a new project is a collaboration with the Prof. Siwick to perform ultrafast electron diffraction (UED). A first set of materials are charge density wave systems (NbSe2, TiSe2, TaSe2 and TaS2) where optical excitations couple to the electron and phonon dynamics. The ability to measure the structures with sub-picosecond time scales is needed o study these effects