RUI: NMR Studies of Hidden Order and Quantum Criticality

RUI：隐藏序和量子临界性的核磁共振研究

• 批准号: 0604015
• 负责人: Oscar Bernal
• 金额: $ 18.8万
• 依托单位: California State L A University Auxiliary Services Inc.
• 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: 2006-07-01 至 2011-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0604015&HistoricalAwards=false
• 关键词: RUI; NMR; Studies; Hidden; Order

Non TechnicalThis is an experimental condensed matter project. It concentrates on the investigation of phase transitions and the possibility of discovering new states of matter. The materials used for this investigation are named "electron-correlated systems." These are mostly inter-metallic compounds whose thermal and conductance properties are very different from normal metals such as copper or silver, for instance. Electron-correlated materials are of current interest for science and technology because of the many states in which they can be found. For instance, they can display superconductivity, magnetism, antiferromagnetism, quadrupolar ordering, colossal magnetoresistance, and of particular interest for this project, hidden order and the so-called "non-Fermi liquid behavior." Nuclear-magnetic resonance techniques will be used to study the properties of URu2Si2 and UCu5-xNix with the goal of understanding the nature of their unusual behavior. Undergraduate and masters-level students will be trained in the techniques of magnetic resonance, radio-frequency electronics, cryogenics, and computer interface. One aspect of this project is related to K-12 education. Some Los Angeles area teachers will have a chance to deepen their understanding of the science standards and concepts taught at the elementary school level and will learn about experimental techniques that will enhance instruction around those standards. The collaboration will involve meetings at the elementary school sites and Cal State L.A., as well as curricular trips for the students.TechnicalThis experimental condensed matter project will concentrate on the study of phase transitions and intrinsic inhomogeneous properties in electron-correlated materials. It will aim to characterize the static and dynamic properties of local magnetic and electric-field-gradient distributions in two specific materials and their compounds: URu2Si2 and UCu1-xNix. The former undergoes a phase transition involving an as-yet unknown order parameter. Among the possible ordered states being proposed are quadrupolar, octupolar, spin chiral, and orbital antiferromagnetism. NMR will be used to probe the internal fields and their local distributions with the goal of elucidating the true order parameter. UCu4Ni and other compositions near x=1 are disordered by design and present non-Fermi liquid behavior related to a quantum critical point. NMR will be used to study the magnetic disorder and to elucidate to what extent it or quantum criticality is responsible for the unusual behavior at low temperatures. One main question to address is that of the universality of quantum critical phenomena, since both ordered and disordered non-Fermi liquid systems seem to behave very similarly near absolute zero. This project has a K-12 education component in which Los Angeles area teachers will deepen their understanding of the science standards and concepts taught at the elementary school level and learn experimental techniques that will enhance instruction. Meetings at the elementary school sites and Cal State L.A. as well as curricular trips for the students will be carried out.

这是一个实验性的凝聚态项目。它专注于相变的研究和发现物质新状态的可能性。用于这项研究的材料被命名为“电子相关系统”。“这些主要是金属间化合物，其热性能和传导性能与铜或银等普通金属非常不同。电子相关材料是目前科学和技术的兴趣，因为它们可以在许多状态下被发现。例如，它们可以显示超导性，磁性，反铁磁性，四极有序，巨磁阻，以及本项目特别感兴趣的隐藏顺序和所谓的“非费米液体行为”。“核磁共振技术将用于研究URu 2Si 2和UCu 5-xNix的性质，目的是了解它们不寻常行为的性质。本科生和硕士生将接受磁共振、射频电子学、低温学和计算机接口技术的培训。该项目的一个方面与K-12教育有关。一些洛杉矶地区的教师将有机会加深他们对小学水平的科学标准和概念的理解，并将学习实验技术，以加强围绕这些标准的教学。合作将包括在小学和加州州立大学洛杉矶分校举行的会议，技术这个实验凝聚态项目将集中在电子相关材料的相变和内在不均匀性的研究。它的目的是表征两种特定材料及其化合物：URu 2Si 2和UCu 1-xNix中局部磁场和电场梯度分布的静态和动态特性。前者经历了一个相变，涉及一个迄今未知的序参量。在可能的有序状态被提出的是四极，八极，自旋手征和轨道反铁磁性。核磁共振将用于探测内部场及其局部分布，目的是阐明真正的序参量。UCu 4 Ni和接近x=1的其他组合物通过设计是无序的，并且呈现与量子临界点相关的非费米液体行为。核磁共振将被用来研究磁无序，并阐明在何种程度上它或量子临界性是负责在低温下的不寻常的行为。要解决的一个主要问题是量子临界现象的普遍性，因为有序和无序的非费米液体系统似乎在绝对零度附近表现得非常相似。该项目有一个K-12教育部分，其中洛杉矶地区的教师将加深他们对小学水平的科学标准和概念的理解，并学习实验技术，这将提高教学。在小学和加州州立大学洛杉矶分校举行会议。并为学生提供课程旅行。