Magnetic and electronic excitations in low-dimensional and nanostructured materials

低维和纳米结构材料中的磁和电子激发

• 批准号: RGPIN-2017-04429
• 负责人: Cottam, Michael
• 金额: $ 2.19万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=711037
• 关键词: Magnetic; electronic; excitations; low; dimensional

Research on magnetic materials with one or more lengths in the submicron range, as in low-dimensional nanostructures and arrays, is driven by their immense technological potential (for high-frequency devices, magnetic memories, fast switches, etc). For theory there is a need to understand at a fundamental level the dynamical processes on these length scales. This provides the primary motivation for this proposed theoretical research on the collective magnetic excitations (or waves) together with the electronic excitations. Taking into account the challenging effects due to surfaces and interfaces is important, since nanostructured magnetic materials may display novel characteristics that are absent in their bulk constituent materials. I will study the linear and nonlinear dynamics of magnetic spin waves in arrays of magnetic nano-elements and the related electronic and magnetic effects in carbon-based nanomaterials like graphene. For example, the expanding field of magnonics concerns artificial media like patterned thin films with a repeating (or periodic) variation in their magnetic properties. The frequencies and directions of the spin waves can be controlled using this periodicity and an applied magnetic field, as the basis for device applications. In spintronics there are also moving electronic charges, giving electric currents in the materials; these influence the spin waves allowing further device applications. In the nonlinear dynamics the effects of interactions between the spin waves come into play, and I will study these on the small length scales. Some nonlinear effects that I will focus on include spin-wave decay and instability, particularly in a strong microwave field, and the magnetic Bose-Einstein condensation. The choices of magnetic elements in their periodic or quasiperiodic arrays provide a variety of situations for exploiting new properties for magnetic device applications. Methods include many-body and quantum-field theories (diagrammatic methods, Green's functions, response theory). From previous work I have expertise in specialized methods for spin systems, which I will adapt for nanomaterials in nonlinear regimes with a microwave pumping field being applied. I will utilize collaborations with experimentalists using inelastic light scattering, ferromagnetic and electron-spin resonance, and microwave spectroscopy. My research will be significant for insights to dynamical processes at very small length scales and may lead to new developments for high-frequency devices. Understanding the quantum statistics in these systems when they are far from equilibrium (due to the microwave fields) or at higher temperatures (when nonlinear processes are enhanced) will be important aspects of this work. A better knowledge of the magnetic effects in graphene nanostructures is an important goal for new applications in low-dimensional materials.

在亚微米范围内具有一个或多个长度的磁性材料（如低维纳米结构和阵列中）的研究是由其巨大的技术潜力驱动的（对于高频设备，磁性记忆，快速开关等）。就理论而言，有必要在基本层面上理解这些长度尺度上的动态过程。这为这项提出的关于集体磁激励（或波浪）以及电子激发的理论研究提供了主要动机。考虑到由于表面和界面引起的具有挑战性的影响很重要，因为纳米结构材料可能会显示出大量组成材料中没有的新型特征。 我将研究磁性纳米元素阵列中磁性自旋波的线性和非线性动力学以及碳基纳米材料（如石墨烯）中的相关电子和磁效应。例如，镁质的扩展领域涉及人造介质（如具有图案化的薄膜），其磁​​性具有重复（或周期性）变化。可以使用此周期性和应用磁场作为设备应用的基础来控制自旋波的频率和方向。在Spintronics中，还具有移动的电子电荷，在材料中提供了电流。这些影响旋转波，允许进一步的设备应用。在非线性动力学中，自旋波之间的相互作用发挥了作用，我将在小长度尺度上研究它们。我将重点关注的一些非线性效应包括自旋波衰减和不稳定性，尤其是在强的微波场和磁性玻璃纤维凝结中。磁元素在其周期性或准二元阵列中的选择提供了各种情况，用于利用用于磁性设备应用的新属性。 方法包括多体和量子场理论（示意方法，格林的功能，响应理论）。从以前的工作中，我具有用于旋转系统的专业方法的专业知识，我将适应非线性制度中的纳米材料，并应用微波抽水场。我将使用非弹性光散射，铁磁和电子旋转共振以及微波光谱法利用与实验者的合作。我的研究对于在很小的长度尺度上的动态过程的见解将是重要的，并且可能导致高频设备的新发展。当这些系统远离平衡（由于微波场）或更高温度（增强非线性过程）时，了解这些系统的量子统计数据将是这项工作的重要方面。更好地了解石墨烯纳米结构中的磁效应是低维材料中新应用的重要目标。