Low-Energy Spectroscopy of Correlated Systems

9705442施莱辛格这是一个研究体系的新项目，在这些体系中，电子相互作用的影响使物理学超越了简单的非相互作用固体理论的领域。对于这样的系统，通常在红外中有一个特征能量标度，它将强相关的低能区域与相互作用效应不那么显着的高能区域分开。这项拟议的研究试图使用光谱测量来探测这一关键红外范围内的动力学，从而发展对相关系统的理解。要研究的具体系统包括近藤绝缘体、混价系统、磁序驱动的金属-绝缘体相变和超导体-绝缘体相变系统。这些实验将阐明这些系统中电荷动力学的本质，并探索电荷动力学、磁性、无序和局域化之间的关键关系。这些结果将为这一凝聚态物理学前沿领域的理论工作提供检验和刺激。这是一个研究体系的新项目，在这些体系中，电子相互作用的影响使物理学超越了简单的非相互作用固体理论的领域。尽管我们对金属和半导体的基本理解是建立在电子不相互作用的理论基础上的，但未来的电子技术将越来越多地包括电子之间相互作用发挥作用的材料。因此，重要的是要充分了解这些相关电子系统的电子性质，其中发生的现象不能通过系统组件(电子和原子核)的知识轻易预测，而是以一种不明显的方式出现在它们之间的相互作用中。(例子包括磁性和超导性。)这一建议是为了研究红外光谱区的电子动力学，它包括与形成最相关的电子态有关的能量范围，因此特别重要。要研究的系统包括可被视为相关半导体的稀土化合物，以及磁性和导电性之间的相互作用导致显著效应(例如，巨磁电阻)的氧化物系统。这些实验结果有望刺激和检验凝聚态物理学前沿领域的理论成果。***

9705442 Schlesinger This is a new project to study systems in which the effects of electron interactions extend the physics beyond the domain of simple non-interacting theories of solids. For such systems there is generally a characteristic energy scale in the infrared which separates a strongly correlated low-energy region from a high-energy region in which interaction effects are much less significant. The proposed research seeks to use spectroscopic measurements to probe the dynamics in this crucial infrared range and thereby to develop an understanding of correlated systems. Specific systems to be studied include Kondo insulators, mixed-valent systems, metal- insulator transitions driven by magnetic order, and superconductor- insulator transition systems. These experiments will elucidate the nature of the charge dynamics in these systems, and explore crucial relationships between charge dynamics, magnetism, disorder and localization. Results will provide both a test of and a stimulus for theoretical work in this area at the forefront of condensed matter physics. %%% This is a new project to study systems in which the effects of electron interactions extend the physics beyond the domain of simple non-interacting theories of solids. Although our basic understanding of metals and semiconductors is built on theories of non-interacting electrons, future electronic technologies will increasingly include materials in which interactions between electrons play a role. It is thus important to fully understand the electronic properties of these correlated electron systems, in which phenomena occur that cannot be readily predicted from a knowledge of the system components (the electrons and nuclei), but rather, arise in a non-obvious way from the interactions between them. (Examples include magnetism and superconductivity.) This proposal is directed toward the study o f electron dynamics in the infrared spectral region, which encompasses the energy range relevant to the formation of most correlated electron states and is thus particularly important. Systems to be studied include rare-earth compounds that can be viewed as correlated semiconductors, and oxide systems where an interplay between magnetism and electrical conductivity leads to striking effects (e.g., giant magnetoresistance). The experimental results can be expected to stimulate and test theoretical efforts in this area at the forefront of condensed matter physics. ***