Study of Excitations in Cuprate Superconductors and Related Systems by Inelastic Scattering of Visible, Ultraviolet, and X-Ray Photons

通过可见光、紫外线和 X 射线光子的非弹性散射研究铜酸盐超导体及相关系统的激发

• 批准号: 9705131
• 负责人: Miles Klein
• 金额: $ 20.08万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-07-15 至 2001-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9705131&HistoricalAwards=false
• 关键词: Study; Excitations; Cuprate; Superconductors; Related

w:\awards\awards96\num.doc 9705131 Klein This experimental research project focuses on the unusual electronic properties of those cuprate compounds which are "parent compounds" of the cuprate superconductors. These compounds exhibit correlated electron behavior, and in particular antiferromagnetism. In the superconducting phases, the residual antiferromagnetism is poorly understood. This experimental project will clarify the residual antiferromagnetism by scattering experiments using visible, ultraviolet, or x-ray photons, to study excitations wherein an electron from an occupied initial state makes a transition to an unoccupied final state, accompanied by a redistribution of charge. The objectives are (1) to understand how electronic charge excitations couple to electronic spin excitations (magnons) and to lower energy electronic charge excitations, which may include superconducting gap excitations; (2) to validate inelastic x-ray scattering techniques for studying electronic charge excitations at finite momentum transfer; (3) to better understand electronic excitations in conventional metals and semiconductors through use of inelastic x-ray scattering techniques. The experiments will employ a combination of low energy and high energy photon probes. These include low energy optical absorption; resonance Raman scattering, especially resonant two-magnon scattering; UV excited Raman scattering, and two new techniques, inelastic s-ray scattering spectroscopy (IXSS) and resonant inelastic x-ray scattering spectroscopy (RIXSS), which provide data at finite momentum transfer. The work is expected to advance knowledge of both strongly-correlated electronic systems and of inelastic x- ray scattering. %%% This research project experimentally studies the unusual behavior of the cuprate compounds which when "dop ed" become high temperature superconductors. These "parent compounds" exhibit unusual behavior, including antiferromagnetism, which is to some extent retained in the superconducting phases. It is believed that a better understanding of the normal and parent phases of these materials is necessary for understanding of the unusually strong superconductivity when suitably doped. The present experimental project will address the important questions concerning the antiferromagnetic behavior, by a combination of measurements of the scattering of photons (visible, ultraviolet, and x-ray) by these compounds. A portion of the work will utilize the Raman effect, and another portion will utilize a new advanced experimental technique, inelastic x-ray scattering, which is now available at the Advanced Photon Source, a world-class synchrotron light source which is located near the Argonne National Laboratory. The work will advance knowledge of both strongly-correlated electronic systems and also of the inelastic x-ray scattering process. The study of these materials and their unusual magnetism is valuable as a testing ground for theories of magnetic, optical, and electrical properties of the cuprates, which can then be more confidently applied to other systems; and in the search for novel properties and new compounds which may find new application in technology. This research project is interdisciplinary in nature and involves both graduate and postdoctoral students who will be excellently trained to enter positions in industry, government or education. ***

w：\awards\awards96\num.doc 9705131 Klein 这 实验研究项目的重点是那些铜酸盐化合物的不寻常的电子性质，这些化合物是“母体 化合物” 铜酸盐超导体的。 这些化合物表现出相关的电子行为，特别是反铁磁性。在超导阶段，剩余反铁磁性知之甚少。 这 实验项目 将 澄清 剩余反铁磁性 通过使用可见光、紫外线或X射线光子的散射实验来研究激发，其中电子从被占据的初始状态跃迁到未被占据的最终状态，伴随着电荷的重新分布。目的是（1）了解电子电荷激发如何耦合到电子自旋激发（磁振子），并降低 能量电子电荷激发，可能包括超导间隙激发;（2）验证用于研究有限动量电子电荷激发的非弹性x射线散射技术 转让; （三） 更好地 理解 通过使用非弹性X射线散射技术在常规金属和半导体中的电子激发。实验将采用低能和高能光子探针的组合。 这些方法包括低能光吸收、共振拉曼散射，特别是共振双磁振子散射、紫外光激发的拉曼散射和共振共振双磁振子散射。 散射，和两种新技术，非弹性s射线散射光谱（IXSS）和共振非弹性x射线散射光谱（RIXSS），提供数据在有限的动量转移。这项工作有望推进强相关电子系统和非弹性X射线散射的知识。 %这个研究项目通过实验研究了 当“掺杂艾德”时， 高温超导体这些“母体化合物”表现出不寻常的行为，包括反铁磁性，这在一定程度上保留在超导相中。 据信，更好地理解这些材料的正常相和母相对于理解异常强的 适当掺杂时的超导性。 的 目前的实验 项目将解决重要的 关于反铁磁行为的问题，通过测量这些化合物的光子散射（可见光，紫外线和X射线）的组合。这项工作的一部分将利用拉曼效应，另一部分将利用一种新的先进实验技术，非弹性x射线散射，这是现在可用的 在 先进的光子源， 一 世界一流的同步加速器光源，位于阿贡国家实验室附近。 这项工作将推进强相关电子系统和非弹性X射线散射过程的知识。对这些材料及其不寻常的磁性的研究是有价值的，可以作为铜酸盐的磁性，光学和电学性质理论的试验场，然后可以更有信心地应用于其他系统;并在寻找新的性质和新的化合物，这些化合物可能会在技术上找到新的应用。这个研究项目是跨学科的性质，涉及研究生和博士后学生谁将得到良好的培训，进入行业，政府或教育职位。 ***