Quantum Phase Transitions in Model Magnets and Switchable Mirrors

非技术性摘要在最低温度下，量子效应主宰着物理学。然而，即使在室温这样高的温度下，当材料从金属到绝缘体，从磁体到非磁体，从普通导体到超导体的状态变化时，也可以感受到量子力学的影响。这个计划将研究两个这样的状态变化的模型和有用的量子系统。第一种是氢化钇薄膜，通过简单地改变氢的浓度或用紫外线照射，它可以从闪亮的镜子变成透明的窗户。第二种是普通铬，其磁性可以通过压力或合金化来调节。该提案强调了通过博士学位整合研究和教育的努力。培训涵盖广泛的技能和设施，重点是招聘妇女和少数民族，本科课程开发，以及个人承诺向公众和社区学校推广。它还描述了机构计划的发展和监督，这些计划使物理科学和商业的学生能够研究工业进口问题，以及芝加哥大学与100%非洲-该大学在芝加哥南区开设的美国特许学校。技术摘要该提案旨在探讨量子相变和涨落的基本性质两个模型实验系统。第一个是元素Y和La的氢化膜中的金属-绝缘体转变，选择具有强相关性但没有与电荷局部化相关的结构转变的材料。重点将是定义电子-电子相互作用，无序和非线性动力学所扮演的角色。绝缘状态也作为一个模型的相互作用库仑玻璃，和研究的长时间弛豫，记忆效应和噪声谱将继续进行。第二个系统包括唯一的元素反铁磁体Cr的单晶。实验的重点将是高压金刚石对顶砧室研究，它可以抑制纯铬的自旋密度波过渡顺利到T = 0。输运和x射线技术的结合应该阐明在磁量子临界点的电荷密度波，自旋密度波和潜在的超导不稳定性的相互作用。该提案强调了通过博士学位整合研究和教育的努力。培训涵盖广泛的技能和设施，重点是招募妇女和少数民族，本科课程开发，以及个人和机构对公众和社区学校的宣传。

NON-TECHNICAL ABSTRACTAt the lowest temperatures, quantum effects dominate the physics. However, even at temperatures as high as room temperature, the effects of quantum mechanics can be felt when a material changes state from metal to insulator, from magnet to non-magnet, from ordinary conductor to superconductor. This proposal will investigate two such changes of state in model and useful quantum systems. The first is a thin film of yttrium hydride, which can switch from shiny mirror to transparent window by simply changing the hydrogen concentration or by illuminating with ultraviolet light. The second is common chromium, whose magnetic character can be tuned with pressure or by alloying. This proposal highlights efforts to integrate research and education through Ph.D. training across a broad spectrum of skills and facilities, with an emphasis on recruiting women and minorities, undergraduate curriculum development, and personal commitments to outreach to the general public and neighborhood schools. It also describes the development and oversight of institutional programs that match students from the physical sciences and business to study problems of industrial import as well as a partnership between the University of Chicago and the 100% African-American Charter School that the University operates on the South Side of Chicago.TECHNICAL ABSTRACT This proposal aims to probe the fundamental nature of the quantum phase transition and fluctuations in two model experimental systems. The first is the metal-insulator transition in hydrogenated films of elemental Y and La, select materials with strong correlations but without a structural transformation tied to the localization of charge. The emphasis will be on defining the roles played by electron-electron interactions, disorder, and the non-linear dynamics. The insulating state also serves as a model for the interacting Coulomb glass, and studies of the long-time relaxation, memory effects and noise spectra will be pursued. The second system involves single crystals of the only elemental antiferromagnet, Cr. The experimental focus will be on high-pressure diamond anvil cell studies which can depress pure Cr's spin-density-wave transition smoothly to T = 0. A combination of transport and x-ray techniques should illuminate the interplay of the charge-density-wave, spin-density-wave and potentially superconducting instabilities at the magnetic quantum critical point. This proposal highlights efforts to integrate research and education through Ph.D. training across a broad spectrum of skills and facilities, with an emphasis on recruiting women and minorities, undergraduate curriculum development, and both personal and institutional outreach to the general public and neighborhood schools.