Study of Anomalous Magnetism and Superconductivity in Selected Lanthanides, Alkalis and Noble Metals Under Extreme Pressure

简单的材料更容易理解，而复杂的材料更有趣，更有可能导致创新的应用。在这项研究中，极高的压力，高达2-3百万大气压，被应用于非常简单和柔软的材料，比如碱金属。这种极端的压力能够不断地将这些金属转化为令人惊讶的复杂材料，这些材料可能会成为超导、铁磁性甚至绝缘的材料。单个样本可以通过极端压缩来表现出如此异常的行为，这一事实使人们能够更深入地了解是什么使它们起作用。另一方面，这种增强的理解有助于设计在环境压力下具有有用性能的材料。在被称为“稀土”的元素中，高压已被发现在非常高的温度下诱导磁有序。如果运气好的话，这项工作可能会导致高性能永磁体的发展，这是一种在日常生活中无处不在的材料。提出的实验为本科生和研究生提供了学习和发展多种基本实验技术的机会；这些学生还受益于与美国和国外团体的科学合作。【技术摘要】该奖项的研究主要有两个方向。第一种是典型的简单自由电子金属，如碱金属，在极端压缩下转化为具有高度异常电子性质的材料。这些特性包括在相对高温下的超导性，金属-半导体或金属-绝缘体的转变，甚至泡利顺磁到流动铁磁的转变。本项目将深入研究选定碱金属及其合金和化合物在超高压下的超导相图和临界磁场行为。第二个推力方向是由PI小组在极端压力下发现的温度远高于环境温度的磁顺序演变而来的。这提高了一种优于当前记录保持者Nd-Fe-B的永磁材料的可能性。进一步感兴趣的材料是氢化物，特别是最近在190 K附近发现了二氢化硫的超导性。提议的实验为本科生和研究生提供了一个学习和发展重要实验室技术的绝佳机会，并与美国和国外的团队合作。

Non-Technical AbstractWhereas simple materials are easier to understand, complex materials are more interesting and more likely to lead to innovative applications. In this single investigator award extremely high pressures, as high as 2-3 million atmospheres, are applied to very simple and soft materials, like the alkali metals. Such extreme pressures are able to continuously transform these metals into surprisingly complex materials that may become superconducting, ferromagnetic or even insulating. The fact that a single sample can be brought through extreme compression to exhibit such anomalous behavior allows one to gain a deeper understanding of what makes them tick. This enhanced understanding, on the other hand, facilitates the design of materials with useful properties at ambient pressure. In elements called "rare-earths", high pressures have been found to induce magnetic ordering at very high temperatures. With some luck this work could lead to the development of superior permanent magnets, a ubiquitous material in everyday life. The proposed experiments give undergraduate and graduate students the opportunity to learn and develop a multitude of essential experimental techniques; these students also benefit from scientific collaborations with groups both in the US and abroad.Technical AbstractThe research in this single investigator award has two primary thrust directions. The first is the transformation under extreme compression of canonical simple free-electron metals, such as the alkali metals, into materials with highly anomalous electronic properties. These properties include superconductivity at relatively high temperatures, metal-semiconductor or metal-insulator transitions or even Pauli paramagnetic to itinerant ferromagnetic transitions. This project will study in depth to ultrahigh pressures the superconducting phase diagram and critical magnetic field behavior of selected alkali metals as well as their alloys and compounds. The second thrust direction has evolved out of the discovery by the PI's group of magnetic order at temperatures well above ambient in selected lanthanides under extreme pressures. This raises the possibility of a permanent magnet material superior to the current record holder Nd-Fe-B. Further materials of interest are the hydrides, particularly following the very recent discovery of superconductivity in sulfur dihydride near 190 K. The proposed experiments give undergraduate and graduate students an excellent opportunity to learn and develop important laboratory techniques and collaborate with groups both in the US and abroad.