Exotic Magnetic Ground States and Ground State Selection in Quantum Materials

量子材料中的奇异磁基态和基态选择

• 批准号: RGPIN-2019-07084
• 负责人: Gaulin, Bruce
• 金额: $ 6.92万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=715711
• 关键词: Exotic; Magnetic; Ground; States; State

The ground states of most magnetic materials, and all magnetic materials which are well understood, are characterized by long range order and conventional elementary excitations, such as spin waves. We are specifically interested in families of new magnetic materials, where this isn't the case; that is where a disordered low temperature phase can persist due to the presence of very strong spin fluctuations. This is a very topical area of contemporary condensed matter research as it is widely believed that if a conventional ordered state can be suppressed at low temperatures, it opens a window for an exotic ground state to be manifest. Appropriate quantum disordered states are thought to possess qualitatively new and remarkable physical properties, such as delocalized quantum spin excitations, that may provide a platform for quantum computation. Strong spin fluctuations can be encouraged in three ways in magnetic materials: magnetic moments can decorate local geometries (typically based on triangles and tetrahedra) in solids which are incompatible with a simple ordered state this is referred to as geometrical frustration; S=1/2 and effective S=1/2 magnetic moments, which support extreme quantum fluctuations, can be made to decorate the lattice; and finally the magnetic lattice can be effectively two or one dimensional due to a three dimensional crystal structure which is made of a stacking of magnetic planes, or a bunching together of magnetic chains. This proposal seeks to explore new magnetic materials which do precisely this. By carrying out advanced characterization, primarily with new neutron and x-ray scattering techniques we aim to elucidate the nature of the exotic ground states which ensue in such materials, such that the principles that underlie the novel phenomena they display can be fully understood. This proposal seeks to carry out programs of neutron scattering measurements on several families of exotic magnetic materials that we will grow in single crystalline, polycrystalline and epitaxial thin film form. We are in the midst of a renaissance in the capabilities available to carry out forefront inelastic neutron scattering. The net result is that new neutron scattering instrumentation provides qualitatively different, and much more comprehensive, information on materials than was possible six years ago. This proposal seeks to apply this new infrastructure to several topical problems related to exotic magnetic ground states in new materials. A crucial component and starting point for the themes of this proposal is a program of sophisticated materials preparation and crystal growth which will provide new magnetic materials in appropriate forms. We are exceptionally well positioned, both with respect to our capacity to produce materials of interest, and with respect to access and expertise associated with the new neutron scattering infrastructure, to make real progress in this very topical area of condensed matter physics.

大多数磁性材料以及所有众所周知的磁性材料的基态都具有长程有序和传统基本激发（例如自旋波）的特征。我们对新型磁性材料系列特别感兴趣，但情况并非如此；那就是一个 由于存在非常强的自旋波动，无序的低温相可能会持续存在。这是当代凝聚态物质研究的一个非常热门的领域，因为人们普遍认为，如果传统的有序态可以在低温下被抑制，那么它就会为一种奇异的基态的显现打开一扇窗户。 适当的量子无序态被认为具有全新且显着的物理特性，例如离域量子自旋激发，这可能为量子计算提供平台。 在磁性材料中，可以通过三种方式促进强烈的自旋波动：磁矩可以装饰固体中与简单有序状态不相容的局部几何形状（通常基于三角形和四面体），这被称为几何挫败；可以使S=1/2和有效S=1/2磁矩支持极端的量子涨落，来装饰晶格；最后，由于由磁平面堆叠或磁链聚集在一起组成的三维晶体结构，磁晶格可以有效地是二维或一维的。 该提案旨在探索能够做到这一点的新磁性材料。通过进行先进的表征，主要是利用新的中子和 X 射线散射技术，我们的目标是阐明此类材料中出现的奇异基态的性质，以便能够充分理解它们所表现出的新现象背后的原理。 该提案旨在对我们将以单晶、多晶和外延薄膜形式生长的几种奇异磁性材料进行中子散射测量计划。我们正处于可用于执行最前沿非弹性中子的能力的复兴之中 散射。 最终结果是，新的中子散射仪器提供了与六年前不同的、更全面的材料信息。该提案旨在将这种新的基础设施应用于与新材料中的奇异磁性基态相关的几个热门问题。 该提案主题的一个关键组成部分和起点是复杂材料制备和晶体生长计划，它将提供适当形式的新型磁性材料。无论是在生产感兴趣材料的能力方面，还是在与新中子散射基础设施相关的获取和专业知识方面，我们都处于非常有利的位置，可以在凝聚态物理这个非常热门的领域取得真正的进展。