Inelastic Light Scattering as a Probe of Electronic Correlations

该奖项支持关于一类电子相互作用强的材料的理论研究和教育活动。这些材料中的许多在足够低的温度下变成超导。超导现象的信号是无能量损失的导电。如果能发现在足够高的温度下表现出超导性的材料，那么它们就可以用于电力的传输。该奖项支持的研究旨在更深入地了解电子运动中相关性的作用，这些相关性是由化学成分中含有铁元素的超导材料家族中的强电子相互作用引起的。这些材料可能是开发在更高温度下（可能达到室温）表现出超导性的新材料的垫脚石。PI将发展理论来理解从铁基超导体散射光的实验中获得的数据的含义。电子之间的强相互作用导致每个电子的状态由所有其他电子的运动决定。由此产生的电子-电子相互作用使电子自组织并使它们对外部刺激作出集体反应。PI和他的研究团队将研究在广泛的铁基超导体材料中出现的集体行为。PI将关注三种类型的电子自组织的相互作用：超导性、磁性和结构秩序。普通金属导体中的单个电子通过与导致损耗的材料缺陷相互作用而失去能量，而超导体的集体流动特性是刚性的，不能轻易中断，从而导致无损耗的电力传输。当固体内部的微观基本磁体都指向同一个方向，形成磁体的北极时，磁性就出现了。结构有序是由电子倾向于特定的传播方向引起的。PI将在单一理论框架内对所有这些集体现象进行全面研究。这项研究将通过会议和期刊出版物，以及现有的面向在校儿童的推广计划，对科学界和公众产生广泛的影响。PI将进一步设计结合现代理论物理发展的大学课程，以培养下一代。该奖项将支持和促进研究生的培训和教育，寻求他们的理论凝聚态物理博士学位。该奖项支持理论研究和教育活动，目的是促进对铁基超导体和低维电子材料中电子集体行为的理解。PI将专注于光探测铁基超导体中的集体现象。由于集体现象是有序的指纹，PI将研究有序参数的结构和相互作用，以及与超导机制密切相关的问题，以及磁性，晶格变形和超导之间可能的共生关系。本研究的主要目的是促进对不同宏观秩序开始时出现的集体行为的理解，以及有序状态之间的相互作用和竞争。PI旨在推进描述层状超导体和相互作用电子液体的相关效应和集体响应的分析技术。在研究中还将使用各种标准的现代方法。PI旨在促进对经典和量子相变开始时对称破缺的普遍方面的理解。本项目还包括低维系统中自旋输运的研究。这些系统中的集体行为是由于单个电子感受到的微观场的相互作用引起的自组织而产生的。PI将研究电子量子相干性的增强，如拉曼光谱中的锐模式所示，以及相关影响电子动力学的方式。这项研究将通过会议和期刊出版物，以及现有的面向在校儿童的推广计划，对科学界和公众产生广泛的影响。PI将进一步设计结合现代理论物理发展的大学课程，以培养下一代。该奖项将支持和促进研究生的培训和教育，寻求他们的理论凝聚态物理博士学位。

NON-TECHNICAL SUMMARY This award supports theoretical research and educational activities on a class of materials in which electrons interact strongly. Many of these materials become superconducting at sufficiently low temperature. The phenomenon of superconductivity is signaled by the conduction of electricity without energy loss. If materials can be discovered that exhibit superconductivity at sufficiently high temperature, then they could be used for the transmission of electrical power. This award supports research geared toward deeper understanding of the role of correlations in electron motion that arise from strong electron interaction in a family of superconducting materials which contain the element iron in their chemical composition. These materials may be stepping stones to developing new materials which exhibit superconductivity at higher temperatures, perhaps reaching up to room temperature. The PI will develop theory to understand the implications of data obtained from experiments in which light is scattered off iron-based superconductors. Strong interactions between electrons cause the state of each electron to be determined by the motion of all other electrons. The resulting electron-electron interactions cause the electrons to self-organize and cause them to respond collectively to external stimuli. The PI and his research team will study collective behavior that arises in the broad class of iron-based superconductor materials. The PI will focus on the interplay of three types of electronic self-organization: superconductivity, magnetism, and structural order. While the individual electrons in ordinary metallic conductors lose their energy through interaction with material imperfections leading to losses, the collective flow characteristic of superconductors is rigid and cannot be easily disrupted leading to loss free transmission of electricity. Magnetism appears when the microscopic elementary magnets inside the solid all point in the same direction setting the north pole of a magnet. Structural ordering is caused by the electrons preferring a specific propagation direction. The PI will carry out a comprehensive study of all these collective phenomena within a single theoretical framework.The research will have a broad impact on the scientific community and the public through conferences and journal publications, and through an existing outreach program to school children. The PI will further design university courses that incorporate modern developments in theoretical physics to train the next generation. This award will support and contribute to the training and education of graduate students seeking their PhD degrees in theoretical condensed matter physics. TECHNICAL SUMMARYThis award supports theoretical research and educational activities with the goal of advancing understanding of the collective behavior of electrons in iron-based superconductors and low-dimensional electronic materials. The PI will focus on collective phenomena in iron-based superconductors probed by light. As the collective phenomena are the fingerprints of ordering, the PI will investigate the structure and interplay of order parameters, and closely related questions of the mechanism of superconductivity and possible symbiotic relationships among magnetism, lattice deformation and superconductivity. The major objective of the proposed research is to advance understanding of collective behavior emergent at the onset of different macroscopic orders, and the interplay and the competition among ordered states. The PI aims to advance analytical techniques for describing correlation effects and collective response of layered superconductors and interacting electron liquids. A variety of standard modern methods will also be used in the research. The PI aims to contribute to the understanding of universal aspects of symmetry breaking at the onset of classical and quantum phase transitions. This project also includes a study of spin transport in low dimensional systems. The collective behavior in these systems sets in due to the interaction-induced self-organization of microscopic fields felt by individual electrons. The PI will investigate enhancement of electronic quantum coherence as shown by sharp modes in Raman spectra and the ways in which correlations affect the electron dynamics.The research will have a broad impact on the scientific community and the public through conferences and journal publications, and through an existing outreach program to school children. The PI will further design university courses that incorporate modern developments in theoretical physics to train the next generation. This award will support and contribute to the training and education of graduate students seeking their PhD degrees in theoretical condensed matter physics.