Frustration and Order in Heavy Fermions on the Shastry-Sutherland Lattice

* 技术摘要 * 该奖项旨在阐明最初定位在稀土基重费米子化合物的f轨道上的电子可以被诱导加入构成费米表面（FS）的巡回状态的过程，以及伴随这种电子脱限跃迁的电子结构的临界波动。 我们将研究在几何阻挫的Shastry-Sutherland晶格上形成的重费米子中阻挫在抑制磁序中的作用。设想了两种不同的基态：自旋液体，其中传导电子与波动时刻解耦，其电子因此被排除在FS之外，以及费米液体，其中强烈的近藤效应使f-电子离域，其现在被纳入扩展的FS中。这两个无序态在T=0时被一个纯粹的电子跃迁分开，由大FS态和小FS态之间的波动驱动。新材料的合成，以支持PI和她的合作者的测量计划是这个项目的中心主题。参与的本科生和研究生将获得各种不同的合成和实验技术的实践和便携式经验。这项研究广泛利用了国家研究设施，包括NIST和橡树岭国家实验室的中子散射中心。 * 非技术摘要 * 虽然所有材料在高温下都是无序的，在它们的构型中没有可辨别的模式或相关性，但随着温度的降低，有序相（如超导性或磁性）的出现是压倒性的。该项目旨在阐明具有最极端形式的秩序的系统的性质，这些秩序恰好发生在绝对零度的温度下。 这种相变的量子力学性质是至关重要的，其结果是，即使在非零温度下，正常的行为，如热或电的传导也会发生巨大的变化。 在这里，几何约束与晶格的磁矩将被用来实现这样的T=0的过渡，和他们的属性将使用在NIST和橡树岭国家实验室进行的中子散射实验进行研究。新材料的合成，以支持PI和她的合作者的测量计划是这个项目的中心主题。参与的本科生和研究生将获得各种不同的合成和实验技术的实践和便携式经验。

****Technical Abstract****This award aims to explicate the process by which electrons that are initially localized on the f-orbitals of rare earth based heavy fermion compounds can be induced to join the itinerant states comprising the Fermi surface(FS), and the critical fluctuations of the electronic structure that accompany this electronic de-confinement transition. The role of frustration in suppressing magnetic order in heavy fermions that form on the geometrically frustrated Shastry-Sutherland lattice will be investigated. Two distinct ground states are envisaged: a spin liquid where the conduction electrons are decoupled from the fluctuating moments, whose electrons are consequently excluded from the FS, and a Fermi liquid, where a strong Kondo effect delocalizes the f-electrons, which are now incorporated in an expanded FS. These two non-ordered states are separated at T=0 by a purely electronic transition, driven by fluctuations between the large and small FS states. The synthesis of new materials to support both the measurement program of the PI and those of her collaborators is a central theme of this project. Participating undergraduate and graduate students will gain practical and portable experience in a variety of different synthesis and experimental techniques. This research makes extensive use of national research facilities, including neutron scattering centers at NIST and Oak Ridge National Laboratory. ****Non-Technical Abstract****While all materials are disordered at high temperatures, with no discernible patterns or correlations in their configurations, the onset of an ordered phase such as superconductivity or magnetism is overwhelmingly favored as the temperature is reduced. This project seeks to explicate the properties of systems with the most extreme form of order, which occurs exactly at a temperature of absolute zero. The quantum mechanical nature of such a phase transition is paramount, with the result that normal behaviors like the conduction of heat or electricity are drastically modified- even at nonzero temperatures. Here, geometrical constraints associate with a lattice of magnetic moments will be used to realize such T=0 transitions, and their properties will be studied using neutron scattering experiments carried out at NIST and at Oak Ridge National Laboratory. The synthesis of new materials to support both the measurement program of the PI and those of her collaborators is a central theme of this project. Participating undergraduate and graduate students will gain practical and portable experience in a variety of different synthesis and experimental techniques.