Collaborative Research: Spin Correlations and Spin-Orbit Effects in New Quantum Materials

该奖项支持俄亥俄大学和佛罗里达大学理论小组之间开展的合作研究和教育活动，与阿根廷和巴西的科学家密切联系，将技术和专业知识结合起来，解决材料研究中的重要和局部问题。该项目将重点探索电子材料的电子特性，其中电子的自旋自由度受到其空间（轨道）运动的强烈影响。自旋和轨道自由度的耦合是最近重新发现的一种现象，它已经被观察到影响金属，半导体和绝缘体的许多特性，并且可以通过施加电场来增强。该研究旨在提供一种广泛适用的描述，描述自旋轨道相互作用如何在不同的外场和微观环境下与排斥电子-电子相互作用竞争。这种描述将适用于装饰或嵌入石墨烯（一种由碳原子组成的二维材料，厚度为一个原子），其他二维单晶和三维材料，其中电子激发的能量与它们的动量成线性比例。该项目预计将为自旋轨道相互作用的结果提供基本见解，并推进对材料的理解，以便更好地进行实验表征，并最终在磁性、自旋敏感电子学和量子信息处理方面应用器件。项目组还计划在其不同的站点开展一些教育活动，包括培训美国和拉丁美洲的初级研究人员，以及为与研究相关的普通K-12读者提供引人入胜的书籍的外联工作。该奖项将支持理论研究和教育活动，旨在对最近发现的材料（包括石墨烯及其衍生物、二维二硫族化合物和Kagome晶体、三维狄拉克半金属及其异质结构）中的自旋轨道相互作用及其与库仑排斥的竞争有基本的了解。除了它们迷人而有些奇特的物理特性外，这些材料还承诺了各种令人兴奋的技术应用，从磁学和自旋电子学到新的碳基器件，甚至量子信息处理。项目团队计划采用并进一步发展适当的理论技术，包括数值重整化群、密度矩阵重整化群、连续和紧密结合的散射矩阵方法，以及对感兴趣的系统的低能量有效哈密顿量的场理论表示。这些方法在处理强相关问题方面已被证明是可靠的，它们的互补性使合作具有独特的优势。由俄亥俄大学和佛罗里达大学的理论小组组成的研究小组与阿根廷和巴西的科学家密切合作，将设法改进这些技术，以扩大其适用范围，特别是在与时间有关和非平衡现象有关的方面。物质相之间的竞争，以及它们通过外部探针的控制和修改，是需要研究的两个主要问题。一个特别的重点将是理解和指导实验发展，以阐明在存在外部电磁场和应变场的情况下内在量子对称性所起的作用。项目组还计划在其不同的站点开展一些教育活动，包括培训美国和拉丁美洲的初级研究人员，以及为与研究相关的普通K-12读者提供引人入胜的书籍的外联工作。

NON-TECHNICAL SUMMARYThis award supports collaborative research and educational activities carried out among theory groups at Ohio University and the University of Florida, working in close connection with scientists in Argentina and Brazil, to combine techniques and expertise and tackle important and topical problems in materials research. The project will focus on exploring electronic properties of materials where the electron's spin degree of freedom is strongly affected by their spatial (orbital) motion. The coupling of spin and orbital degrees of freedom is a recently rediscovered phenomenon that has been observed to impact a number of properties in metals, semiconductors, and insulators, and can be enhanced by applied electric fields. The research to be carried out is designed to provide a widely applicable description of how spin-orbit interactions compete with repulsive electron-electron interactions under different external fields and microscopic environments. This description will be applied to decorated or intercalated graphene (a two-dimensional material made of carbon atoms that is one atom thick), other two-dimensional single crystals, and three-dimensional materials in which the energy of the electronic excitations is linearly proportional to their momentum. The project is expected to provide fundamental insights into the consequences of spin-orbit interactions as well as to advance the understanding of materials for better experimental characterization and eventual device applications in magnetism, spin-sensitive electronics, and quantum information processing. The project team also plans a number of educational activities across its different sites, including the training of junior researchers in the US and Latin America, as well as outreach efforts that bring in writers to produce engaging books for a general K-12 audience on topics related to the research.TECHNICAL SUMMARYThis award will support theoretical research and educational activities aimed at achieving a fundamental understanding of spin-orbit interactions and their competition with Coulomb repulsion in recently discovered materials that include graphene and its derivatives, two-dimensional dichalcogenides and Kagome crystals, three-dimensional Dirac semimetals, and their heterostructures. In addition to their fascinating and somewhat exotic physical properties, these materials promise a variety of exciting technological applications, from magnetics and spintronics to new carbon-based devices, and even quantum information processing. The project team plans to employ and further develop appropriate theoretical techniques, including the numerical renormalization group, the density-matrix renormalization group, and continuous and tight-binding scattering-matrix approaches, as well as field-theoretical representations of low-energy effective Hamiltonians for the systems of interest. These approaches are proven and reliable in treating strongly correlated problems, and their complementarity gives the collaboration a unique advantage. The research team consisting of theory groups at Ohio University and the University of Florida, working in close collaboration with scientists in Argentina and Brazil, will seek to advance the techniques to enhance their range of applicability, especially in connection with time-dependent and non-equilibrium phenomena. Competition between phases of matter, and their control and modification through external probes, are the two main issues to be investigated. A particular focus will be on understanding and guiding experimental developments, with the goal of elucidating the role that intrinsic quantum symmetries play in the presence of external electromagnetic and strain fields. The project team also plans a number of educational activities across its different sites, including the training of junior researchers in the US and Latin America, as well as outreach efforts that bring in writers to produce engaging books for a general K-12 audience on topics related to the research.