Ab-Initio Studies of Spin-Orbit and Electron-Phonon Effects in Metals

金属中自旋轨道和电子声子效应的从头算研究

• 批准号: 0706493
• 负责人: Steven Louie
• 金额: $ 24万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-12-15 至 2011-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0706493&HistoricalAwards=false
• 关键词: Ab; Initio; Studies; Spin; Orbit

TECHNICAL SUMMARY:This award supports theoretical and computational research and education in the area of the electronic structure of metals, with particular emphasis on properties mediated by the spin-orbit and electron-phonon interactions. These interactions induce subtle modifications in the electronic structure and accurately calculating the consequences represents a significant challenge. A major focus of the proposed work will be to further develop efficient and accurate algorithms for treating spin-orbit effects which can effectively address the need to sample the entire Brillouin zone in metallic systems. The method developed here capitalizes on a means for representing the bulk electronic structure in terms of partially occupied spinor Wannier functions and will be applied to two types of problems: First, in regard to spin relaxation in nonmagnetic metals, a previously proposed mechanism of spin relaxation, resulting from the combination of spin-orbit and electron-phonon coupling, will be investigated from first-principles. Initial studies will focus on trivalent metals such as aluminum, which are particularly challenging due to the occurrence of spin-orbit "hot spots" on the Fermi surface. Second, spin-orbit effects in ferromagnets in which time-reversal symmetry may be spontaneously broken will be investigated computationally from first principles. The specific properties of study are the intrinsic dc anomalous Hall effect, magneto-optical effects such as magnetic circular dichroism, and orbital magnetization. Applications will be made first to itinerant ferromagnets such as iron, nickel, and cobalt. In parallel with the ab-initio studies, theoretical work will be carried out to reveal the interconnections between the various spin-orbit effects in ferromagnets. The second major focus of research is to extend the Wannier-interpolation algorithms to calculate the electron-phonon coupling matrix elements, by representing the physics in terms of both localized electronic and vibrational lattice Wannier functions. The resulting technique will be applied to both spin-relaxation mechanism and superconductivity in boron-doped diamond. This project is expected to lead to fundamental theoretical and algorithmic advances aiming to accurately and reliably calculating spin-orbit and electron-phonon physics in metals. It will provide an improved understanding of the mechanisms by which the spin-orbit interaction gives rise to the dc anomalous Hall conductivity in ferromagnets. It will extend to finite frequency the algorithms developed for the anomalous Hall conductivity, and allow for the exploration of magneto-optical effects. It will uncover rather subtle sum rules which connect these dynamical properties to the static orbital magnetization.NON-TECHNICAL SUMMARY:This award supports theoretical and computational research and education that aims to develop and apply methods that will enable computers to calculate magnetic properties of and phenomena in materials with a focus on understanding how electrons, the tiny units of charge and magnetism in a material, move through materials when driven by electric and magnetic fields. The discovery of new magnetic phenomena as well as learning how to control known magnetic phenomena continues to lead to new technologies and conspicuously to advances in information technology. These technologies include spintronics, photomagnetic devices, magnetic memory and storage devices and magnetoelastic materials. Computer assisted design of magnetic materials and devices still requires theoretical and methodological advances. This research deals aims to develop a method at the level of atoms and electrons for accurately calculating magnetic properties of materials. Such methods will enable scientists and engineers to open new frontiers and technologies.

技术摘要：该奖项支持金属电子结构领域的理论和计算研究和教育，特别强调自旋-轨道和电子-声子相互作用所介导的性质。这些相互作用导致电子结构的微妙变化，准确计算结果是一个巨大的挑战。拟议工作的一个主要重点将是进一步开发有效和准确的算法来处理自旋-轨道效应，从而有效地满足对金属系统中的整个布里渊区进行采样的需要。这种方法利用了一种用部分占据的旋量Wannier函数来表示体电子结构的方法，并将应用于两类问题：第一，对于非磁性金属中的自旋驰豫，将从第一性原理出发研究先前提出的自旋-轨道和电子-声子耦合的自旋驰豫机制。最初的研究将集中在铝等三价金属上，由于费米表面上出现了自旋轨道“热点”，这些金属特别具有挑战性。其次，我们将从第一性原理出发，计算研究铁磁体中的自旋轨道效应，在这些自旋轨道效应中，时间反转对称性可能自发破缺。研究的特殊性质是本征直流反常霍尔效应、磁圆二向色性等磁光效应和轨道磁化。将首先申请巡回铁磁体，如铁、镍和钴。在从头计算研究的同时，还将开展理论工作，以揭示铁磁体中各种自旋轨道效应之间的相互联系。第二个主要的研究重点是通过用局域电子和振动格子Wannier函数来表示物理，扩展Wannier插值法来计算电子-声子耦合矩阵元。这项技术将同时应用于掺硼金刚石的自旋弛豫机制和超导电性。这个项目有望带来基本的理论和算法进步，旨在准确和可靠地计算金属中的自旋轨道和电子-声子物理。这将有助于更好地理解自旋-轨道相互作用引起铁磁体中直流反常霍尔电导的机制。它将把为反常霍尔电导率开发的算法扩展到有限频率，并允许探索磁光效应。它将揭示相当微妙的求和规则，将这些动力学性质与静态轨道磁化联系起来。非技术摘要：该奖项支持理论和计算研究与教育，旨在开发和应用方法，使计算机能够计算材料中的磁性和现象，重点是了解电子，即材料中的微小电荷和磁性单位，在电场和磁场的驱动下如何在材料中运动。新的磁现象的发现以及学习如何控制已知的磁现象继续导致新的技术，尤其是信息技术的进步。这些技术包括自旋电子学、光磁设备、磁记忆和存储设备以及磁弹性材料。磁性材料和器件的计算机辅助设计仍然需要理论和方法上的进步。这项研究旨在开发一种在原子和电子水平上精确计算材料磁性的方法。这种方法将使科学家和工程师能够开辟新的领域和技术。