Spin Waves in Disordered Potentials: Interplay between Disorder, Nonlinearity, and Incoherence

无序势中的自旋波：无序、非线性和不相干之间的相互作用

• 批准号: 1407962
• 负责人: Mingzhong Wu
• 金额: $ 48.21万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1407962&HistoricalAwards=false
• 关键词: Spin; Waves; Disordered; Potentials; Interplay

Non-Technical AbstractWave theory is fundamental to physics, underlying everything from radar to fiber optics to cell phone communications. Waves occur in magnetic materials, where the magnetic spin precesses in a wave pattern, propagating energy and information. Magnetic materials are important in many technological contexts, including solid-state hard drives. In a perfectly ordered magnetic material a wave would propagate smoothly; however, real materials have disorder, imperfections that lead to localization of waves, so that information or energy gets trapped in a certain location in the material. This research seeks to understand many unanswered questions about localization of waves in disordered magnetic materials. In particular, three main questions are addressed: (1) Does coherence matter? Lasers, for example, are coherent, and spin waves can be too. (2) How does nonlinearity destroy localization? Nonlinearity means the whole is not the sum of the parts. In spin waves the strength of this effect can be controlled, and its impact on localization explored. (3) Can chaos cause delocalization? Real materials often exhibit chaos. Does chaos allow a localized wave to escape? To support this research and create tomorrow's scientists, the project provides extensive training opportunities for students at undergraduate and graduate levels, especially interdisciplinary cross-training between experimental and theoretical physics. Outreach to high schools in Colorado is accomplished through the Colorado State University "Little Shop of Physics" program, focusing on those in disadvantaged areas. Outreach to the broader scientific community occurs via organizing of scientific conferences, workshops, and symposia.Technical AbstractAnderson localization and Aubry-André localization have both attracted rather considerable interest across a number of disciplines in recent years due to their ubiquitous nature. Theoretical studies have yielded many predictions about the effects of coherence and nonlinearity on localization that are of great fundamental importance but are often controversial or debatable. The research in this project not only settles several current debates on localization, but also provides first experimental justifications to a number of theoretical predictions. As such, the project deepens the understanding of the interplay between disorder, nonlinearity, and coherence in general. Furthermore, the research enhances the understanding of spin-wave dynamics in magnetic thin films and damping processes in magnetic materials with disordered defects. Specifically, the studies make use of spin waves in yttrium iron garnet (YIG) thin film strips. Disordered potentials for spin waves are developed by two approaches: (1) the fabrication of disordered grooves on the surfaces of YIG strips and (2) the development of disordered local field variations by depositing meander lines on the YIG strips and passing electric currents through the lines. Two types of disordered potentials are considered: random potentials and quasi-periodic potentials. The former is used to study Anderson localization, while the latter is used for the study of Aubry-André localization. The research consists of both experimental and theoretical efforts. It is carried out through integral collaborations between Mingzhong Wu's experimental group at Colorado State University and Lincoln Carr's theoretical group at Colorado School of Mines. The new program has transformative impacts in view of promising potential applications of localization effects. For example, the energy density within a localized mode can be several orders of magnitude larger than that of the incident wave, and this huge field enhancement has potential applications for energy harvest, storage, and conversion. In addition to mentorship at undergraduate to graduate levels and outreach as described above, the principal investigators are jointly engaged in curriculum development, focusing on bringing up-to-date applications and experimental demonstrations into graduate core courses in electrodynamics and classical dynamical systems.

非技术抽象波理论是物理基础，从雷达到光纤再到手机通信的基础。波浪发生在磁性材料中，其中磁性自旋在波模式中以传播能量和信息传播。在许多技术环境中，磁性材料很重要，包括固态硬盘驱动器。在完美有序的磁性材料中，波会平稳地传播。但是，实际材料具有无序，导致波浪定位的缺陷，因此信息或能量被困在材料中的某个位置。这项研究旨在了解有关波浪在无序磁性材料中的定位的许多未解决的问题。特别是，解决了三个主要问题：（1）连贯性很重要吗？例如，激光是连贯的，并且旋转波也可以。 （2）非线性如何破坏本地化？非线性意味着整体不是部分的总和。在自旋波中，可以控制这种效果的强度，并探讨了其对本地化的影响。 （3）混乱会引起离域化吗？真实的材料经常暴露出混乱。混乱是否允许局部波逃脱？为了支持这项研究并创建明天的科学家，该项目为本科和研究生水平的学生提供了广泛的培训机会，尤其是实验物理学和理论物理学之间的跨学科交叉训练。科罗拉多州高中的宣传是通过科罗拉多州立大学的“小物理商店”计划完成的，重点是灾难地区。通过组织科学会议，研讨会和专题讨论会，对更广泛的科学界进行了宣传。技术抽象和安德森的本地化和奥布里·安德烈的本地化在近年来由于无处不在的性质引起了许多学科的兴趣。理论研究对连贯性和非线性对本地化的影响产生了许多预测，这些预测非常重要，但通常是有争议的或值得期讨论的。该项目中的研究不仅解决了有关本地化的当前辩论，而且还为许多理论预测提供了第一个实验依据。因此，该项目一般来说，该项目加深对疾病，非线性和连贯性之间相互作用的理解。此外，该研究增强了对磁性薄膜中的自旋波动力学的理解，并在缺陷障碍的磁性材料中阻尼过程。具体而言，研究利用了Yttrium铁石榴石（YIG）薄膜条中的自旋波。旋转波的无序电位通过两种方法开发：（1）在YIG条表面上制造无序的凹槽，以及（2）通过将曲折线沉积在YIG条上并通过线路传递电流，从而发展出无序的局部场变化。考虑了两种类型的无序电位：随机电位和准周期电位。前者用于研究安德森本地化，而后者则用于研究Aubry-André定位。该研究包括实验和理论努力。它是通过科罗拉多州立大学的Mingzhong Wu实验小组与林肯·卡尔（Lincoln Carr）在科罗拉多州矿业学院的理论小组之间进行的整体合作进行的。鉴于有望实现本地化影响的潜在应用，新计划具有变革性的影响。例如，局部模式内的能量密度可能比事件波大的数量级大几个数量级，并且这种巨大的场增强具有潜在的能量收获，存储和转换的应用。如上所述，除了在本科生到研究生水平和外展活动外，首席研究人员还共同从事课程开发，重点是将最新的应用和实验演示介绍到电子和经典动态系统中的研究生核心课程中。