High Field Studies of Strongly Correlated Electron Systems

该项目研究一类材料中的电子相关性，其中强有效相互作用导致独特的物理效应。 这项研究主要是实验性的，利用了最近在美国可用的强磁场。 这些材料主要是单晶形式，包括UPt3、URu2Si2、U2Pt2In和LiV2O4。该项目使用超声波，磁力测量，运输和强磁场中的热力学测量，在低温和高压。 强关联系统拥有丰富的相图，其中存在许多彼此接近的不同可能的电子状态。 外部扰动可以将系统从相图的一部分驱动到相邻的一部分。 强磁场就是这样一种扰动，它可以对电子产生显著的影响，从而提供一个窗口来检查它们之间的强相关性。 由于高磁场、低温和高压的极端环境，所提出的测量提出了挑战。 实验结果可能会增加对高温超导体和巨磁阻合金等技术重要材料的理解。 通过这项研究获得的知识和信息通过弗吉尼亚大学物理服务器上维护的强相关材料在线资源中心传播。 参与该项目的博士后和博士前学生将接受先进仪器、材料处理和分析方面的培训，为他们在学术界和工业界的职业生涯做好准备。这项研究将研究一类材料中电子之间相互作用的性质，这些相互作用足够强，可以导致独特和新颖的物理效应。 这些材料主要是由在其外壳中具有未成对f和d电子的元素形成的。 这项研究是实验性的，涉及使用最近在美国可用的最强的人造磁场。 将被研究的材料是完美的结晶形式，因此可以使用超声波，磁力测量，电输运和热力学等技术进行高质量的测量。 强磁场会对材料产生多种影响。 在金属中最常见的效应是电阻的增加。 足够强的磁场可以使金属变成绝缘体。 在为拟议的研究选择的材料中，这种影响特别引人注目。 因此，磁场的应用提供了一个窗口来检查所选材料中电子之间相互作用的性质。 这些材料的电子性质与其他几种重要的技术系统，如高温超导体和巨磁阻合金有许多相似之处。 对于所选择的测量，高磁场的极端环境带来了许多挑战。 正在开发新的实验技术来克服这些挑战，这些技术本身可能会带来技术回报。 一个在线资源中心，以传播通过拟议的研究获得的知识和信息将保持在弗吉尼亚大学的物理服务器。 参与该项目的研究生和本科生将接受先进仪器、材料处理和分析方面的培训，为他们在学术界、工业界和政府的广泛职业生涯做好准备。

This project investigates electron correlations in a class of materials where the strong effective interaction leads to unique physical effects. The research is primarily experimental and exploits intense magnetic fields which have recently become available in the United States. The materials are primarily in single crystal form and include UPt3, URu2Si2, U2Pt2In and LiV2O4. The project uses ultrasound, magnetometry, transport and thermodynamic measurements in intense magnetic fields, at low temperatures and high pressures. Strongly correlated systems possess a rich phase diagram with a number of different possible electronic states existing in close proximity to each other. An external perturbation can drive the system from one part of the phase diagram to a neighboring one. Intense magnetic fields are one such perturbation which can have a marked impact on the electrons and thus provide a window to examine the strong correlations between them. The proposed measurements present challenges due to the extreme environment of high magnetic fields, low temperatures and high pressures. The results experiments may lead to an increased understanding technologically important materials such as high temperature superconductors and giant magnetoresistive alloys. The knowledge and information obtained through this research is disseminated through an on-line resource center for strongly correlated materials maintained on the University of Virginia physics server. Post and pre-doctoral students involved in this project will receive training in advanced instrumentation, materials handling and analysis that will prepare them for careers in academia and industry.%%%This research will examine the nature of the interactions between electrons in a class of materials where these interactions are strong enough to lead to unique and novel physical effects. These materials are formed primarily from elements with unpaired f and d - electrons in their outer shells. The research is experimental and involves the use of the most intense man made magnetic fields which have recently become available in the United States. The materials that will be studied are in perfect crystalline form so that high quality measurements using techniques such as ultrasound, magnetometry, electrical transport and thermodynamics can be performed. Intense magnetic fields can have several effects on materials. The most commonly observed effect in metals is the increase of resistance. A strong enough magnetic field can turn a metal into an insulator. Such effects in the materials chosen for the proposed research are particularly dramatic. The application of a magnetic field thus provides a window to examine the nature of the interactions between electrons in the chosen materials. The electronic properties of these materials bear many similarities to those of several other technologically important systems such as high temperature superconductors and giant magnetoresistive alloys. For the measurements chosen the extreme environment of high magnetic fields presents many challenges. New experimental techniques are being developed to surmount these challenges and by themselves may offer technological pay-offs. An on-line resource center to disseminate the knowledge and information obtained through the proposed research will be maintained on the University of Virginia physics server. Graduate and undergraduate students involved in the project will receive training in advanced instrumentation, materials handling and analysis that will prepare them for wide ranging careers in academia, industry and the government.