RUI: NMR Studies of Hidden Order and Quantum Criticality

这是一个实验性的凝聚态物质项目。它集中于研究相变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”。这些大多是金属间化合物，其热和导电性能与普通金属（例如铜或银）有很大不同。电子相关材料是当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秩序和所谓的“非费米液体行为”。核磁共振技术将用于研究URu2Si2和UCu5-xNix的性质，目的是了解它们不同寻常行为的本质。本专业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。这个项目的一个方面与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。合作将包括在小学场地和加州州立大学洛杉矶分校的会议，以及学生的课程旅行。本实验凝聚态项目将集中研究电子相关材料的相变和本征不均匀性。它将旨在表征两种特定材料及其化合物：URu2Si2和UCu1-xNix中局部磁场和电场梯度分布的静态和动态特性。前者经历了一个涉及未知阶参量的相变。在被提出的可能的有序态中有四极性、八极性、自旋手性和轨道反铁磁性。核磁共振将用于探测内部场及其局部分布，目的是阐明真正的有序参数。在x=1附近的UCu4Ni和其他成分被设计为无序的，并表现出与量子临界点相关的非费米液体行为。核磁共振将用于研究磁性紊乱，并阐明它或量子临界在多大程度上对低温下的异常行为负责。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在接近绝对零度时的行为似乎非常相似。该项目有一个K-12教育的组成部分，在这个部分中，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，并学习将加强教学的实验技术。在小学和加州州立大学洛杉矶分校的会议以及学生的课程旅行将进行。

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.