CHIME — CHirality-Induced dynamics of Magnetization and Electrons

该研究项目旨在探索手性磁系统的动力学特性，为未来可能的器件应用提供相关的新材料。信息存储需求的指数级增长增加了对信息存储设备新范式的需求。目前的信息存储设备要么易失性（如随机存取存储器），要么性能有限（如硬盘驱动器）。磁化的电气控制一直是下一代高性能非易失性器件可能应用的焦点。最近在自旋轨道耦合和逆对称性破缺方面的突破，产生了新的手性电子态和在对称系统中被禁止的新现象。除了理解这些新现象的基本兴趣之外，已经证明，当操纵受这种手性影响的磁织构时，它可以显着提高能量效率。以前的研究大多采用自上而下或自下而上的方法。自上而下的方法是首先观察现象学，然后引入现象学术语来描述它，但这很少允许微观理解。另一方面，自下而上的方法是通过第一性原理计算来进行预测，但它对系统参数的依赖使得它很难提供一个一般的理解。CHIME的目标是通过提供简洁、统一、通用和易于实验人员访问的理论描述，在这两种方法之间提供一个有效的桥梁。目标现象的例子包括自旋轨道转矩、拓扑织构的运动、各向异性磁电阻和自旋波。我们寻求一种简单但仍然包含所有核心微观成分的模型，其参数可以用作实验中的拟合参数，也可以通过第一性原理计算获得直接可预测性和材料设计力。通过这种方式，我们将能够提高对手性磁体的微观和现象学理解，并为器件应用找到优化的结构。我们的分析结果将得到我们小组其他成员的数值模拟的支持。在实验方面，我们计划利用我们与内部团队以及布拉格、剑桥和凯泽斯劳滕的其他外部合作者的富有成效的合作。我们计划将我们的形式推广到其他最近感兴趣的系统，例如拓扑绝缘体，反铁磁体，铁磁体，以及自旋轨道耦合和破缺对称性起关键作用的界面超导二维态。

The proposed research project aims to explore dynamical properties of chiral magnetic systems, which are relevant new materials for possible future device applications. The exponential increase on information storage demand has increased the need to find new paradigms of information storage devices. Currently information storage devices are either volatile (e.g. random access memory) or limited in performance (e.g. hard disk drive). Electric control of magnetization has been the focus for possible applications in the next generation devices that are non-volatile with high performance. A recent breakthrough arising from spin-orbit coupling and broken inversion symmetry, has given rise to new chiral electronic states and new phenomena that are forbidden in symmetric systems. Besides the fundamental interest in understanding these new phenomena, it has been demonstrated that it raises the energy efficiency significantly when manipulating magnetic textures affected by this chirality. Previous research has taken mostly either a top-down or a bottom-up approach. A top-down approach is to observe phenomenology first and then introduce phenomenological terms to describe it, but this does rarely allow microscopic understanding. On the other hand, a bottom-up approach is to carry out a first-principles calculation to make a prediction, but its dependence on system parameters makes it difficult to provide a general understanding. The goal of CHIME is to provide an efficient bridge between the two approaches, by providing theoretical descriptions that are concise, unified, general, and easily accessible to experimentalists. Examples of the target phenomena include spin-orbit torque, motion of topological textures, anisotropic magnetoresistance, and spin waves. We seek a model that is simple but still includes all the core microscopic ingredients, of which the parameters can be used as fitting parameters in experiment as well as be obtained by the first-principles calculations for direct predictability and material design power. In this way, we will be able to raise both microscopic and phenomenological understanding of chiral magnets and find an optimized structure for device applications. Our analytic results will be supported by collaboration with numerical simulations done by other members of my group. Concerning experiments we plan to exploit our fruitful collaboration with the in-house group and other external collaborators in Prague, Cambridge, and Kaiserslautern. We plan to generalize our formalism to other systems of recent interest, such as topological insulators, antiferromagnets, ferrimagnets, and superconducting two-dimensional states at interfaces where spin-orbit coupling and broken symmetry play crucial roles.