CAREER: Novel Electronic and Magnetic Dynamics and Responses in Noncollinear Magnetic Materials

该奖项支持理论和计算研究，旨在揭示与描述所谓的非共线磁性材料中的磁顺序相关的概念和实践挑战。与传统的铁磁体和反铁磁体不同，非共线磁序不能被可视化为平行和反平行的微磁矩阵列。传统上，非共线磁性的研究远远少于铁磁性和反铁磁性，而且应用有限。然而，最近已经发现了几种非共线磁性金属，它们具有令人惊讶的特性，可能会导致有用的电子和自旋电子应用。这个紧密结合的理论计算项目旨在确定非共线磁体耦合电子和磁性动力学的新原理，新的和独特的外场响应函数，并预测具有非共线磁性的新材料系统。该项目有助于寻找具有强电子相互作用的系统的新技术突破。非共线磁体的强耦合自旋和轨道自由度可以用于不同尺度的能量收集中有效的自旋-电荷转换。这个项目的教育部分侧重于对称和大数据，这在当今的物理和材料科学课程中非常重要。通过组织一个关于磁性对称性原理和应用的暑期学校，以及重新设计一个计算材料物理课程来引入机器学习的概念，PI将帮助当地和全国的本科生和研究生获得必要的这些学科的接触，并将其融入他们的专业思维。鉴于该项目的多学科性质，参与研究的本科生和研究生也将接受基础科学和技术方面迎接“量子飞跃”挑战的必要训练。技术总结：与铁磁和反铁磁序相反，非共线磁序不能被可视化为排列在晶格上的平行或反平行磁矩。这些材料在自旋电子学和磁输运中的研究进展一直受到概念和实践挑战的阻碍，这些挑战与缺乏类矢量有序参数和导电电子自旋不守恒有关。这个理论计算结合的项目旨在解决这些挑战，通过以下研究重点：(1)计算搜索由对称引导的新型非共线磁体。群论方法和朗道相变理论将被用于在材料科学数据库中寻找新的非共线磁体，而不是少数已知的例子。(2)非共线磁体的新响应函数、功能和实验探针。用流体力学方法和半经典波包理论来解释非共线磁体中独特的守恒电流及其与流动电子的耦合。量子动力学理论将用于识别新的响应函数，如巨磁电阻的对应，但没有近似的自旋守恒，以及自旋密度极化方面的磁自旋霍尔效应。本文将提出一种利用磁中子散射来探测局部轨道磁化的理论。该项目有助于寻找具有强电子相关性的系统的新技术突破。非共线磁体的强耦合自旋和轨道自由度可以用于不同尺度的能量收集中有效的自旋-电荷转换。这个项目的教育部分侧重于对称和大数据，这在当今的物理和材料科学课程中非常重要。通过组织一个关于磁性对称性原理和应用的暑期学校，以及重新设计一个计算材料物理课程来引入机器学习的概念，PI将帮助当地和全国的本科生和研究生获得必要的这些学科的接触，并将其融入他们的专业思维。鉴于该项目的多学科性质，参与研究的本科生和研究生也将接受基础科学和技术方面迎接“量子飞跃”挑战的必要训练。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NONTECHNICAL SUMMARYThis award supports theoretical and computational research aimed at unraveling the conceptual and practical challenges associated with describing the magnetic order in the so-called noncollinear magnetic materials. Unlike the case for conventional ferromagnets and antiferromagnets, noncollinear magnetic order cannot be visualized as arrays of parallel and antiparallel microscopic magnetic moments. Traditionally noncollinear magnetism has been much less studied than ferromagnetism and anti-ferromagnetism, and has had limited applications. However, recently several noncollinear magnetic metals have been discovered to have surprising properties that could potentially lead to useful electronic and spintronic applications. This cohesive theoretical-computational project aims to identify new principles in the coupled electronic and magnetic dynamics of noncollinear magnets, new and unique response functions to external fields, and to predict new material systems which exhibit noncollinear magnetism.This project contributes to the search for new technological breakthroughs in systems with strong electron interactions. The strongly coupled spin and orbital degrees of freedom in noncollinear magnets may be exploited for efficient spin-charge conversion used in energy harvesting in different scales. The educational component of this project focuses on symmetry and big data, which are overarchingly important in today’s physics and materials science curricula. Through organizing a summer school on Principles and Applications of Symmetry in Magnetism, and redesigning a computational materials physics course to introduce concepts of machine learning, the PI will help local and national undergraduate and graduate students receive necessary exposure to these subjects and integrate them in their professional thinking. Given the multidisciplinary nature of this project, the undergraduate and graduate students involved in the research will also receive the essential training for embracing the “Quantum Leap” challenge in both fundamental science and technology.TECHNICAL SUMMARYNoncollinear magnetic order cannot be visualized as parallel or antiparallel magnetic moments arranged on a crystal lattice, as opposed to ferro- and antiferro-magnetic orders. Recent advancement of the study on such materials in spintronics and magnetotransport has been hindered by conceptual and practical challenges associated with the lack of vector-like order parameters and non-conservation of conduction electrons’ spin. This cohesive theoretical-computational project aims to address these challenges, through the following research thrusts:(1) Computational search for new noncollinear magnets guided by symmetry. Group-theoretic methods and the Landau theory of phase transition will be used to search for new noncollinear magnets in materials science databases beyond the very few known examples. (2) New response functions, functionalities, and experimental probes of noncollinear magnets. A hydrodynamic approach complemented by semiclassical wave-packet theory will be used to elucidate the unique conserved current in noncollinear magnets and its coupling to itinerant electrons. Quantum kinetic theory will be used to identify new response functions such as a counterpart of the giant magnetoresistance but without approximate spin conservation, and the magnetic spin Hall effect in terms of spin density polarization. A theory for using magnetic neutron scattering to detect local orbital magnetization will be formulated. This project contributes to the search for new technological breakthroughs in systems with strong electron correlations. The strongly coupled spin and orbital degrees of freedom in noncollinear magnets may be exploited for efficient spin-charge conversion used in energy harvesting in different scales. The educational component of this project focuses on symmetry and big data, which are overarchingly important in today’s physics and materials science curricula. Through organizing a summer school on Principles and Applications of Symmetry in Magnetism, and redesigning a computational materials physics course to introduce concepts of machine learning, the PI will help local and national undergraduate and graduate students receive necessary exposure to these subjects and integrate them in their professional thinking. Given the multidisciplinary nature of this project, the undergraduate and graduate students involved in the research will also receive the essential training for embracing the “Quantum Leap” challenge in both fundamental science and technology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.