Topology, interactions, and disorder in exotic quantum materials

奇异量子材料中的拓扑、相互作用和无序

• 批准号: RGPIN-2020-06999
• 负责人: Maciejko, Joseph
• 金额: $ 4.44万
• 依托单位: University of Alberta
• 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=718538
• 关键词: Topology; interactions; disorder; exotic; quantum

Ordinary phases of mattersolid, liquid, and gasare distinguished by emergent macroscopic properties, such as rigidity or the lack thereof, which are a consequence of how atoms microscopically arrange themselves, but also transcend the minute details of such arrangements. At temperatures near absolute zero, quantum effects allow for qualitatively new patterns of microscopic arrangements that produce novel emergent properties beyond those of ordinary matter, such as superfluidity, magnetism, and superconductivity. The field of quantum materials, a key subdiscipline of condensed matter physics, attempts to theoretically understand such quantum phases of matter and the transitions between them, and to experimentally discover materials that realize them. In the past ten years or so, this field has witnessed a veritable revolution. Recognized in part by the 2016 Nobel Prize in Physics, the prediction of topological insulatorswhere an insulating bulk coexists with a robust metallic surfacehas received wide experimental confirmation and evolved into a thriving branch of mainstream condensed matter physics. The discovery of exotic magnetic materials where quantum “fuzziness” is so strong as to completely demagnetize them may signal the long-awaited discovery of the spin liquid, an exotic quantum state of matter first theorized in the 1970s. The unusual behavior of ultrathin materials in strong magnetic fields reveals new cooperative behaviors previously thought impossible, such as the emergence of collective excitations with only a fraction of the charge of an electron. Many of the unusual properties of those exotic quantum materials, such as metallic surface states and fractionalized excitations, may lead to novel technological applications in low-power electronics and quantum computing. A necessary first step towards such applications, the development of a complete theoretical understanding of this bewildering variety of new phenomena is however hindered by the lack of a unified conceptual framework and complicated by the unavoidable presence of imperfections and impurities in real materials. Supported in part by this NSERC Discovery Grant, my research program aims to achieve a deeper and more unified understanding of three broad classes of quantum materialstopological materials, spin liquids, and ultrathin materials in high magnetic fieldsthrough the construction of mathematical models that incorporate both quantum effects and material imperfections, and the analysis of those models via cutting-edge theoretical methods. By training undergraduate research assistants (URAs), graduate students, and postdoctoral fellows (PDFs) in a wide range of broadly applicable analytical and computational skills, this research will help maintain Canada's leadership in the field of quantum materials and will contribute to grow our country's knowledge-based economy.

固体、液体和气体的普通相的特征在于出现的宏观特性，例如刚性或缺乏刚性，这是原子如何在微观上自行排列的结果，但也超越了这种排列的微小细节。在接近绝对零的温度下，量子效应允许产生新的微观排列模式，从而产生超出普通物质的新颖的涌现特性，例如超流动性、磁性和超导性。量子材料领域是凝聚态物理的一个重要分支，它试图从理论上理解物质的量子相以及它们之间的转变，并通过实验发现实现它们的材料。 在过去的十几年里，这个领域发生了一场名副其实的革命。拓扑绝缘体（绝缘体与坚固的金属表面共存）的预测得到了 2016 年诺贝尔物理学奖的部分认可，已得到广泛的实验证实，并发展成为主流凝聚态物理学的一个蓬勃发展的分支。奇异磁性材料的发现，其量子“模糊性”如此之强，以至于可以将它们完全消磁，这可能标志着人们期待已久的自旋液体的发现，这是一种奇异的物质量子态，在 20 世纪 70 年代首次理论化。超薄材料在强磁场中的异常行为揭示了以前认为不可能的新合作行为，例如仅用电子电荷的一小部分就出现集体激发。这些奇异量子材料的许多不寻常特性，例如金属表面态和分级激发，可能会在低功耗电子和量子计算中带来新颖的技术应用。然而，对这种令人眼花缭乱的各种新现象的完整理论理解的发展是迈向此类应用的必要的第一步，但由于缺乏统一的概念框架而受到阻碍，并且由于实际材料中不可避免地存在缺陷和杂质而变得复杂。 在 NSERC 发现补助金的部分支持下，我的研究项目旨在通过构建包含量子效应和材料缺陷的数学模型，并通过尖端理论方法对这些模型进行分析，对三大类量子材料拓扑材料、自旋液体和高磁场中的超薄材料有更深入、更统一的理解。通过对本科生研究助理（URA）、研究生和博士后研究员（PDF）进行广泛适用的分析和计算技能的培训，这项研究将有助于保持加拿大在量子材料领域的领先地位，并将为发展我国的知识型经济做出贡献。