Low Energy Spectroscopy of Complex, Geometrically Frustrated and Strongly Correlated Matter

复杂、几何受挫和强相关物质的低能光谱

• 批准号: 0554796
• 负责人: Zack Schlesinger
• 金额: $ 33万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-15 至 2011-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0554796&HistoricalAwards=false
• 关键词: Low; Energy; Spectroscopy; Complex; Geometrically

Non-Technical:Spectroscopy is an enhanced mode of "seeing" in which one separates photons according to their energy or wavelength. This project centers on the use of spectroscopy to explore, elucidateand understand the fundamental nature and application potential of materials influenced by correlation, frustration and complexity. The nanoscale structure of zirconium tungstate includes surprisingly large open spaces and a sense of atomic freedom know as "underconstraint".Zirconium tungstate also contracts when it is heated, a phenomenon known as negative thermal expansion. Spectroscopic measurements will be utilized to elucidate the relationship between the unusual microscopic structure of this complex compound and the macroscopic phenomenon of negative thermal expansion. This will center on the study of far-infrared phonons. Sodium-cobalt-oxide is similar to cuprate high-temperature superconductors in that it has two-dimensional conducting sheets, however, it is different in that the atomic structure within these sheets is based on triangles rather than squares. The resulting difference in the high-frequency Hall response, i.e., the reaction of electrons in the presence of a magnetic field perpendicular to the sheets, has been predicted to be significant due to the "frustrated" nature of the triangular lattice. This project will seek to measure this effect. Electrons normally repel each other, however, in the context of Tl-doped and In-doped PbTe it has been suggested that they may attract one another.Unexpected changes in the electrical resistance of this unusual doped semiconductor, including superconductivity, have been attributed to such a "negative-U scattering" mechanism. This project will use infrared reflectivity measurements explore and elucidate the fundamental nature of the electron interactions and transport in these exotic materials. This multifaceted project integrates research, education and outreach. Students will be prepared to work in the complex and changing world of modern materials relevant for both their fundamental and applied aspects. Students will also be taught to communicate the importance and excitement of their work to broad audiences through our ongoing outreach efforts in4th, 5th and 6th grade classrooms.Technical:This individual investigator award supports spectroscopic studies of materials in which correlation effects, structural complexity and/or frustration influence macroscopic phenomena. Studies of far-infrared reflectivity in zirconium tungstate and related materials will examine relationships between structural underconstraint, unusual phonon phenomena and negative thermal expansion, as well as possible ice-like behavior and manifestations of geometrical frustration in these complex materials. Measurements of finite-frequency Hall response in layered cobalt oxides will investigate the influence of strong correlations in the context of a triangular lattice for which 3-sided flux-enclosing loops may dominate the response. Studies of the optical and far-infrared reflectivity of Tl- and In-doped PbTe will seek to elucidate the origins of novel transport phenomena observed in these systems where anomalous doping characteristics and transport have been associated with negative-U scattering. This multifaceted project integrates research, education and outreach.Students will be prepared to work in the complex and changing world of modern materials relevant for both fundamental and applied aspects, and to communicate the importance and excitement of their work to broad audiences.

非技术性：光谱学是一种增强的“观看”模式，其中人们根据光子的能量或波长将其分离。 该项目的中心是使用光谱学来探索，阐明和理解受相关性，挫折和复杂性影响的材料的基本性质和应用潜力。 钨酸锆的纳米级结构包括令人惊讶的大开放空间和原子自由感，称为“欠约束”。钨酸锆在加热时也会收缩，这种现象称为负热膨胀。光谱测量将用于阐明这种复杂化合物的不寻常的微观结构和负热膨胀的宏观现象之间的关系。 这将集中在远红外声子的研究。 钠钴氧化物类似于铜酸盐高温超导体，因为它具有二维导电片，然而，不同之处在于这些片内的原子结构是基于三角形而不是正方形。由此产生的高频霍尔响应差异，即，由于三角形晶格的“受抑”性质，在存在垂直于片的磁场的情况下，电子的反应已经被预测为是显著的。本项目将设法衡量这一影响。 电子通常相互排斥，然而，在Tl掺杂和In掺杂的PbTe中，它们可能相互吸引。这种不寻常的掺杂半导体的电阻的意外变化，包括超导性，被归因于这种“负U散射”机制。 这个项目将使用红外反射率测量探索和阐明这些奇异材料中电子相互作用和传输的基本性质。 这一多方面的项目将研究、教育和外联结合在一起。 学生将准备在现代材料的复杂和不断变化的世界中工作，这与他们的基础和应用方面有关。 学生也将被教导沟通的重要性和他们的工作的兴奋，通过我们正在进行的外联工作in 4th，5th和6 th年级classroom.Technical的广泛观众：这个个人研究奖支持材料的光谱研究，其中相关效应，结构复杂性和/或挫折影响宏观现象。 钨酸锆和相关材料的远红外反射率研究将研究结构欠约束，不寻常的声子现象和负热膨胀之间的关系，以及这些复杂材料中可能的冰状行为和几何挫折的表现。 有限频率霍尔响应的测量层状钴氧化物将调查强相关性的影响，在三角形晶格的上下文中，3边磁通封闭回路可能占主导地位的响应。 的光学和远红外反射率的Tl和In掺杂的碲化铅的研究将试图阐明在这些系统中观察到的异常掺杂特性和运输已与负U散射的新的运输现象的起源。 这个多方面的项目整合了研究，教育和推广。学生将准备在复杂和不断变化的现代材料世界中工作，这些材料与基础和应用方面都相关，并将他们工作的重要性和兴奋点传达给广大观众。