Frustrated Quantum Magnetism in Insulators and Metals

该奖项支持在固体中不同情况下局域磁矩量子理论的理论研究和教育。感兴趣的具体主题是量子相位和相变的相互作用局部磁矩在绝缘和金属材料。这一领域已经被一些新材料的发现所取代，这些新材料具有不寻常的性质，挑战了凝聚态物理学的传统范式。该提案的重点将是在特定材料的实验或特定微观模型的数值工作的背景下理论概念的一般发展。研究旨在促进对以下方面的理解：（i）三角形反铁磁体中的量子相变，（ii）自旋有序和无序，（iii）无带隙量子自旋液体，（iv）三维中的去限制量子临界性，（v）重费米子金属中磁性与近藤效应的相互作用。前三个是由大量材料和模型的实验和数值计算激发的。PI旨在发现关键的见解，这些见解将有助于解释实验结果，并有助于提出新的见解，以澄清这些新物质状态的性质及其之间的转换。项目（iv）和（v）是长期研究工作的一部分，旨在利用绝缘磁体理论的直觉建立非费米液体重电子临界点理论。为此，PI将在项目（iv）中探索三维绝缘体中非常规量子临界的可能性。在项目（v）中，他将尝试识别重费米液体中可能驱动磁性转变的配置。PI将在可能的情况下通过麻省理工学院的本科生研究机会计划让本科生参与研究。PI计划写一本书，向广大物理学读者介绍凝聚态物理学中分数量子数的一些令人兴奋的现代发展。非技术性总结：该奖项支持旨在发现物质的新磁态和理解可能发生在它们之间的标准相变理论之外的奇异变换的理论研究和教育。这项研究的动机和刺激的新材料的发现与不寻常的性质，挑战凝聚态物理学的传统范式。本研究的重点将是在实验室和计算机实验的材料和模型的背景下发展理论概念。这是基础研究，有助于我们理解材料和物质的新状态，表现出我们目前理解之外的属性和奇异现象的知识基础。这本身就是一种智力追求，不亚于对宇宙的研究，但它也可能导致新现象的发现和新的设备技术。

TECHNICAL SUMMARY:This award supports theoretical research and education on the quantum theory of localized magnetic moments in diverse circumstances in solids. Specific topics of interest are the quantum phases and phase transitions of interacting localized magnetic moments in both insulating and metallic materials. This area has been invigorated by the discovery of a number of new materials with unusual properties that challenge conventional paradigms of condensed matter physics. The emphasis of this proposal will be on general development of theoretical concepts in the context of either experiments on specific materials or numerical work on specific microscopic models.The research aims to advance understanding of: (i) quantum phase transitions in triangular antiferromagnets, (ii) spin nematic order and disorder, (iii) gapless quantum spin liquids, (iv) deconfined quantum criticality in three dimensions, and (v) the interplay between magnetism and Kondo effect in heavy fermion metals. The former three are motivated by experiments and numerical calculations on a number of materials and models. The PI aims to discover key insights that will be useful in interpreting the results from experiments, and that will help suggest new ones that will clarify the nature of these new states of matter and the transformations among them. Projects (iv) and (v) are part of a long term research effort to exploit intuition from the theory of insulating magnets toward building a theory of non-Fermi liquid heavy electron critical points. To that end the PI will explore the possibility of unconventional quantum criticality in three dimensional insulators in project (iv). In project (v) he will attempt to identify configurations in the heavy Fermi liquid which might drive the transition to magnetism.The PI will involve undergraduates in the research, when possible, through theUndergraduate Research Opportunities Program at MIT. The PI plans to write a book that will introduce some of the exciting modern developments on fractional quantum numbers in condensed matter physics to a broad physics audience.NON-TECHNICAL SUMMARY:This award supports theoretical research and education that aims to discover new magnetic states of matter and to understand exotic transformations that can occur among them that lie outside the standard theory of phase transitions. This research is motivated and stimulated by the discovery of new materials with unusual properties that challenge conventional paradigms of condensed matter physics. The emphasis of this research will be on developing theoretical concepts in the context of laboratory and computer experiments on materials and models.This is fundamental research that contributes to the intellectual foundations of our understanding of materials and new states of matter that exhibit properties and exotic phenomena that lie outside our current understanding. This is an intellectual pursuit in its own right no less fascinating than the study of the universe, but it may also lead to the discovery of new phenomena and to new device technologies.