Novel Phenomena in spin orbit coupled systems

自旋轨道耦合系统中的新现象

• 批准号: 1506707
• 负责人: Vivek Aji
• 金额: $ 24.3万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-15 至 2020-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1506707&HistoricalAwards=false
• 关键词: Novel; Phenomena; spin; orbit; coupled

NONTECHNICAL SUMMARYThis award supports theoretical research and education to study new states of electronic matter with novel functionalities in many body systems. The PI will investigate states involving a large number of electrons in materials that arise from the interplay of two ingredients: 1) the interaction between pairs of electrons, and 2) strong spin-orbit interaction which quantifies the influence of an electron's spin, a fundamentally quantum mechanical phenomenon in which an electron appears to spin like a top, on its motion. Over the last decade a number of new phases of matter have been theoretically proposed and experimentally discovered. In many cases, their unique characteristics can be described with the help of concepts from the branch of mathematics dealing with shape, deformation and topology. The intersection of topology, spin-orbit coupling and many body physics is a rich and current area of study that may lead to new device technologies.The PI will focus investigation on two specific kinds of materials systems. The first kind is comprised of the two-dimensional transition metal dichalcogenides. These are materials that are essentially a single atomic layer thick, made from a transition metal such as the elements Tungsten or Molybdenum, and a chalcogen such as the elements Sulphur or Selenium. The projects explore: i) how the coupling of spin and electron motion can lead to new magnetic properties with the potential for device applications; ii) what new magnetic states of matter are possible due to the interactions; and iii) whether consequences of topology allow for new ways of controlling device characteristics using circularly polarized light. The second kind is comprised of the topological semimetals, which are intermediate between a metal and a semiconductor. The PI will map out the possible phases and phenomena supported in these systems, and in parallel use the lessons learned to develop a better understanding of materials with strong spin-orbit interactions.The research team will include one graduate student who will be trained in the needed technical expertise, and in developing an understanding of real materials. The award will help support an outreach effort at University of California-Riverside, by providing stipends for high school teachers to attend a week long Summer Academy for Teachers hosted by the Physics and Astronomy department. TECHNICAL SUMMARYThis award supports theoretical research and education to study new states of electronic matter with novel functionalities in many body systems. The PI aims to discover and design new states of matter and associated properties arising from the interplay of spin-orbit coupling and interactions in many-body systems. Topologically nontrivial states such as topological insulators and Weyl semimetals arise in non-interacting systems. Natural questions that arise are: What happens when interactions are included? Do the topological aspects survive? Are new correlated phases realized which allow new functionalities? The PI will address these questions in the context of two-dimensional dichalcogenides and three-dimensional Weyl semimetals.The projects on two dimensional dichalcogenides aim to characterize new magnetic phenomena that arise due to unique band structure afforded by spin-orbit coupling. For example the nature of the Kondo effect, where an impurity spin is screened by the host electrons, will be established. Opto-electronic coupling with spin specificity provides a new probe to test and manipulate this correlated phase which will be theoretically analyzed. Nontrivial topology also has potential application in spintronics due to the anomalous velocity acquired by the electrons in external electric fields. The PI will explore these new functionalities and the viability of a nonlocal spin-valve device, and whether these phenomena can be further enhanced in proximity to a magnetic insulator.Weyl semimetals are topological yet possess no energy gap in the bulk. This is due to the topological protection of the band crossings and only interactions that couple nodes with opposite topological charge can open a gap. The PI will characterize the excitonic phases and their properties that arise due to electron-electron Coulomb repulsion. A combination of symmetry considerations, field theoretic techniques, and computation will be utilized to achieve the broad objectives of the program.The research team will include one graduate student who will be trained in the needed technical expertise, and in developing an understanding of real materials. The award will help support an outreach effort at University of California-Riverside, by providing stipends for high school teachers to attend a week long Summer Academy for Teachers hosted by the Physics and Astronomy department.

非技术总结该奖项支持理论研究和教育，以研究在许多身体系统中具有新功能的电子物质的新状态。PI将研究材料中涉及大量电子的状态，这些状态是由两个成分相互作用产生的：1)电子对之间的相互作用，以及2)强烈的自旋-轨道相互作用，它量化了电子自旋对其运动的影响。自旋是一种基本的量子力学现象，在这种现象中，电子似乎像陀螺一样自旋。在过去的十年里，从理论上提出了许多新的物质相，并在实验上发现了它们。在许多情况下，它们的独特特征可以借助与形状、变形和拓扑相关的数学分支中的概念来描述。拓扑学、自旋轨道耦合和许多体物理的交叉是一个丰富和当前的研究领域，可能会导致新的器件技术。PI将集中研究两种特定的材料系统。第一类是由二维过渡金属二卤化物组成。这些材料基本上是单一原子层厚的材料，由过渡金属(如钨或钼)和硫化物(如硫或硒)制成。这些项目探索：i)自旋和电子运动的耦合如何导致新的磁性，具有潜在的设备应用；ii)由于相互作用，物质可能有哪些新的磁性状态；iii)拓扑学的结果是否允许使用圆偏振光控制设备特性的新方法。第二类是介于金属和半导体之间的拓扑半金属。PI将绘制出在这些系统中支持的可能的阶段和现象，并同时利用所学到的经验来更好地理解具有强烈自旋-轨道相互作用的材料。研究小组将包括一名研究生，他将接受所需技术专业知识的培训，并发展对真实材料的理解。该奖项将帮助支持加州大学河滨分校的一项外展工作，为高中教师提供津贴，让他们参加由物理和天文学系主办的为期一周的暑期教师学院。技术总结该奖项支持理论研究和教育，以研究在许多身体系统中具有新功能的电子物质的新状态。PI的目标是发现和设计多体系统中自旋-轨道耦合和相互作用产生的物质的新状态和相关性质。拓扑上的非平凡状态，如拓扑绝缘体和Weyl半金属，出现在非相互作用的系统中。自然产生的问题是：当包括交互时会发生什么？拓扑面还存在吗？是否实现了允许新功能的新的相关阶段？PI将在二维二卤化物和三维Weyl半金属的背景下解决这些问题。关于二维二卤化物的项目旨在表征由于自旋-轨道耦合提供的独特能带结构而产生的新的磁性现象。例如，将确定近藤效应的性质，其中杂质自旋被宿主电子屏蔽。具有自旋专一性的光电耦合为测试和操纵这一相关相位提供了一种新的探针，并将从理论上进行分析。由于电子在外电场中获得的反常速度，非平凡的拓扑学在自旋电子学中也有潜在的应用。PI将探索这些新的功能和非局域自旋阀器件的可行性，以及这些现象是否可以在接近磁性绝缘体的情况下进一步增强。Weyl半金属是拓扑的，但在整体上没有能隙。这是由于对能带的拓扑保护，只有具有相反拓扑电荷的节点之间的相互作用才能打开能隙。PI将表征由于电子-电子库仑排斥而产生的激子相及其性质。将综合运用对称性考虑、场论技术和计算来实现该计划的广泛目标。研究团队将包括一名研究生，他将接受所需技术专长的培训，并发展对真实材料的理解。该奖项将帮助支持加州大学河滨分校的一项外展工作，为高中教师提供津贴，让他们参加由物理和天文学系主办的为期一周的暑期教师学院。