Correlated Electron Physics in Hexaborides: a Unique Experimental Material

9971348Fisk这项研究涉及有序原子晶格的强关联电子行为是如何从某个主体晶格提供的背景下的单原子行为演变而来的。最近的工作表明，立方六硼化物材料中的三维硼网络提供了可以描述为坚固的电子惰性背景，几乎不受这些材料中金属原子的原子替代所干扰。在本研究中，我们将研究致密近藤晶格的发展、近藤绝缘体的演化以及稀薄自由电子气的铁磁性。在强关联材料的实验中，这种干净的主晶格的意外出现给了人们信心，相信还可以找到其他这样的主晶格。这项研究工作的一个重要部分是寻找具有类似性能的新材料。这项研究将涉及研究生和博士后研究助理，他们将接受凝聚态物理和材料科学这一重要领域的培训。材料研究的一个重要目标是设计具有特定性能的新材料，以适应当前的发展和新技术的发现。为此，这项研究试图获得这样一种理解，即预测某个特定原子的排列将具有什么性质。这些有趣的材料通常包括我们所说的活性原子的组合，这些原子的性质敏感地取决于他们所处的环境，以及性质不那么敏感的原子。特别是，在具有活性原子的材料中发现了许多不寻常的性质和在技术上有用的性质，这些原子跨越了分隔磁性和非磁性行为的边界。一类被称为六硼化物的金属间化合物被发现为研究活性原子与其环境之间的相互作用提供了一个异常干净的主体晶格。对这些六硼化物系统的研究将为进一步研究发现具有同样不寻常性质的新材料和类似材料提供方向。这项研究项目非常适合培养下一代凝聚态物理学家和材料科学家，以便在21世纪从事前沿技术领域的工作。

9971348FiskThis research concerns the question of how strongly correlated electronic behavior of an ordered lattice of atoms evolves from the single atom behavior against a background provided by some host lattice. Recent work has shown that the three-dimensional boron network in the cubic hexaboride materials provides what can be described as a robust and electronically inert background that is little perturbed by atomic substitutions for metal atoms in these materials. In the present research the development of the dense Kondo lattice, the evolution of the Kondo insulator and the heretofore inaccessible ferromagnetism of the dilute free electron gas will be investigated. The unexpected occurence of the this clean host lattice for experiments in strongly correlated materials gives confidence that other such host lattices can be found. An important part of this research effort is the search for new materials with similar properties. This research will involve graduate students and postdoctoral research associates who will be trained in an important area of condensed matter physics and materials science. %%%An important goal of materials research is the design of new materials with specified properties which would be suitable for the advance of current as well as the discovery of new technology. Towards this end, this research seeks to gain the understanding that will the prediction what properties a given arrangement of certain atoms will have. The interesting materials contain in general combinations of what we can call active atoms whose properties depend sensitively on the environment they are in, in conjunction with atoms whose properties are much less sensitive. In particular, many unusual properties and ones useful technologically are found in materials with active atoms that straddle the boundary separating magnetic from non-magnetic behavior. A class of inter-metallic compounds called hexaborides has been found to provide an unusually clean host lattice for studying the interaction effects between the active atoms and their environments. The study of these hexaboride systems will suggest directions for further research for the discovery of new and similar materials with equally unusual properties. This research project is eminently suited for the training of the next generation of condensed matter physicists and materials scientists for employment in forefront areas of technology during the 21st Century.***