Theory of magnetic and nonmagnetic excitations in low-dimensional and nanostuctured materials

低维和纳米结构材料中的磁性和非磁性激发理论

• 批准号: 36357-2007
• 负责人: Cottam, Michael
• 金额: $ 2.05万
• 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: 2011
• 资助国家: 加拿大
• 起止时间: 2011-01-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=474655
• 关键词: Theory; magnetic; nonmagnetic; excitations; low

The primary objective of this research is a theoretical study of the wave-like disturbances, known as collective excitations, that can occur in low-dimensional solid structures where typically the length scale in one or more of the dimensions may be as small as a few (or a few tens of) nanometres. The disturbances can, for example, be fluctuations in the magnetization (as in a spin wave or magnon), in atomic vibrations (as in phonons), or in electromagnetic fields (as in polaritons). The types of structures of interest include thin films, multilayers (such as superlattices which have a regular repeat pattern or periodicity), nanowires, nanotubes and nanodots (either singly or formed in arrays). All of these are capable of being fabricated to remarkable precision by modern growth techniques. A common feature is that the waves or excitations are extensively modified due to the very small length scale and the boundary regions (the surfaces and interfaces) in such structures, and therefore may show properties quite different from those in bulk materials. A fundamental understanding of these effects is important, both for the basic physics and for identifying their potential for applications (e.g, as high-frequency nanostructure devices and information storage devices). I am interested in novel aspects concerned with the nonlinear dynamical properties of these structures and materials, i.e., in cases where the waves interact with one another. This is in addition to the need for extending previous work in the linear (or noninteracting) regime to different materials and geometries (e.g. arrays of nanotubes and nanodots, or patterned surfaces). The theoretical methods include the use of advanced analytical techniques (such as many-body theory and quantum field theory) and, in some cases, numerical simulations (such as quantum and classical Monte-Carlo methods). Detailed applications will be made to inelastic light scattering and other experimental techniques for investigating the excitations in these systems. A major emphasis in this project will be to linear and nonlinear spin waves in ordered magnetic materials, where interesting effects can occur because of spatial localization and competing types of interactions.

这项研究的主要目标是对波状扰动（称为集体激励）进行理论研究，这种扰动可能发生在低维固体结构中，通常一个或多个维度的长度尺度可能小至几维。 （或几十）纳米。例如，扰动可以是磁化强度（如自旋波或磁振子）、原子振动（如声子）或电磁场（如极化子）的波动。 感兴趣的结构类型包括薄膜、多层结构（例如具有规则重复图案或周期性的超晶格）、纳米线、纳米管和纳米点（单个或以阵列形式形成）。 所有这些都能够通过现代生长技术以极高的精度制造。 一个共同的特征是，由于此类结构中的长度尺度和边界区域（表面和界面）非常小，波或激励被广泛修改，因此可能表现出与块体材料完全不同的特性。 对这些效应的基本了解对于基础物理学和确定其应用潜力（例如，作为高频纳米结构器件和信息存储器件）都很重要。 我对与这些结构和材料的非线性动力学特性有关的新颖方面感兴趣，即在波彼此相互作用的情况下。 除此之外，还需要将线性（或非相互作用）机制中的先前工作扩展到不同的材料和几何形状（例如纳米管和纳米点阵列或图案化表面）。 理论方法包括使用先进的分析技术（例如多体理论和量子场论），以及在某些情况下的数值模拟（例如量子和经典蒙特卡罗方法）。 将详细应用非弹性光散射和其他实验技术来研究这些系统中的激发。 该项目的重点是有序磁性材料中的线性和非线性自旋波，由于空间局域化和相互作用的竞争类型，可能会出现有趣的效应。