Angular momentum transport in insulators: Magnons and other emergent excitations

非技术：在磁性绝缘体中，磁性（“自旋”）可以在材料中流动，而不会产生电荷流过导电体时发生的加热。这使得自旋电流在未来的低功耗技术中具有吸引力。在大多数磁性绝缘体中，自旋通过波传播，每个波携带一定数量的磁性，但在一些材料中，自旋被认为以更复杂的方式携带，因此它以不同数量的包或不同的时间排列，就好像磁性包彼此捆绑在一起。自旋的流动可以用最近开发的技术来驱动和检测。这个项目使用这些方法来检验几种材料中的自旋流作为温度和其他条件的函数，试图测试这些关于非波状自旋运动的想法。例如，自旋流的波动可以量化每个包所携带的磁性，就像雨滴的波动声可以提供雨滴大小的信息一样。首席研究员正在与主要理论家一起解释这些数据。这些系统中自旋流的基础知识对于充分实现其在未来技术中的潜力至关重要，包括量子信息处理。该项目包括从莱斯大学和附近的少数民族服务机构招募的两名研究生和本科生的研究和交流培训。这些人正在获得宝贵的量子材料经验，以及书面和口头沟通技巧，为他们成为技术劳动力做好准备。研究结果通过出版物和会议报告传播到科学界。PI正在与莱斯大学K12教师培训项目合作，继续通过博客向公众宣传，并通过与莱斯大学格拉斯科克继续教育学院的合作，开发/推出关于材料物理学的终身学习课程。技术：角动量通过自旋自由度传递是未来技术中信息和能量流动的另一种途径。特别感兴趣的是通过磁性绝缘体的自旋传播，在没有欧姆电荷流的情况下具有超低耗散的潜力。最近基于自旋霍尔效应的方法已经能够通过磁振子（晶格中电子的量子化自旋波）测量各种磁有序系统中的自旋输运。这个项目的智力价值在于解决了一些基本的开放性问题，包括：在拥有外来的紧急自旋携带激发态而不是磁振子的材料中，自旋是如何传输的？在多铁性中，自旋输运能否通过与电极化的耦合来控制？自旋输运中噪声的基本限制是什么？测量将比较经典自旋液体、经典自旋冰、量子自旋冰、候选费米子量子自旋液体和多铁质自旋输运中的注入和热驱动自旋输运。噪声技术用于观察和量化自旋散粒噪声，自旋散粒噪声是由于携带自旋激励的离散性而预测的（但尚未观察到的）驱动角动量输运的基本波动。首席研究员正在与主要的理论合作者一起对数据进行解释。自旋传播在信息技术中的应用备受关注，量子自旋液体在量子信息处理中具有潜在的应用前景。这些系统中自旋传播的基础知识对于充分发挥其潜力至关重要。该项目包括从莱斯大学和附近的少数民族服务机构招募的两名研究生和本科生的研究和交流培训。这些人正在获得宝贵的量子材料经验，以及书面和口头沟通技巧，为他们成为技术劳动力做好准备。研究结果通过出版物和会议报告传播到科学界。PI正在与莱斯大学K12教师培训项目合作，继续通过博客向公众宣传，并通过与莱斯大学格拉斯科克继续教育学院的合作，开发/推出关于材料物理学的终身学习课程。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical:In a magnetic insulator, magnetism (“spin”) can be made to flow through the material without the heating that happens when flowing charge through an electrical conductor. This makes spin currents appealing for future low power technologies. In most magnetic insulators, spin travels via waves, each carrying a certain amount of magnetism, but in some materials the spin is thought to be carried in more complicated ways, so that it comes in packets of different amounts or arranged differently in time, as if packets of magnetism are tied to each other. The flow of spin can be driven and detected electrically using recently developed techniques. This project uses these methods to examine the flow of spin in several such materials as a function of temperature and other conditions, to try to test these ideas about non-wave-like spin motion. For example, fluctuations in the flow of spin can quantify the amount of magnetism carried per packet, in the same way that the fluctuating sound of rain gives information about the size of rain drops. The Principal Investigator is working with leading theorists in the interpretation of the data. Foundational knowledge of spin flow in these systems is essential for the full realization of their potential in future technologies, including quantum information processing. This project incorporates the research and communications training of two graduate students as well as undergraduate researchers recruited from Rice and nearby minority-serving institutions. These individuals are gaining valuable experience with quantum materials as well as written and oral communications skills, preparing them for the technological workforce. Results are spread to the scientific community via publications and conference presentations. The PI is working with Rice K12 teacher training programs, continuing outreach to the public via blogging, and developing/presenting a lifelong learning course about the physics of materials through the cooperation of Rice’s Glasscock School for Continuing Studies. Technical:Angular momentum transport via the spin degree of freedom is an alternative channel for the flow of information and energy in future technologies. Of particular interest is the propagation of spin through magnetic insulators, with the potential for ultralow dissipation in the absence of Ohmic charge flow. Recent methods based on the spin Hall effect have enabled the measurement of spin transport in a variety of magnetically ordered systems via magnons, the quantized spin waves of the electrons in the lattice. The intellectual merit of this project is the addressing of fundamental open questions, including: How is spin transported in materials that host exotic emergent spin-carrying excitations rather than magnons? Can spin transport be controlled through coupling to electric polarization in multiferroics? What are the fundamental limitations of noise in spin transport? Measurements will compare injection- and thermally-driven spin transport in classical spin liquids, a classical spin ice, a quantum spin ice, a candidate fermionic quantum spin liquid, and a multiferroic. Noise techniques are used to observe and quantify spin shot noise, the predicted (but not yet observed) fundamental fluctuations in driven angular momentum transport due to the discrete nature of spin-carrying excitations. The Principal Investigator is working with leading theorist collaborators in the interpretation of the data. Spin propagation is of interest for application in information technology, and quantum spin liquids are potentially relevant for quantum information processing. Foundational knowledge of spin propagation in these systems is essential for the full realization of their potential. This project incorporates the research and communications training of two graduate students as well as undergraduate researchers recruited from Rice and nearby minority-serving institutions. These individuals are gaining valuable experience with quantum materials as well as written and oral communications skills, preparing them for the technological workforce. Results are spread to the scientific community via publications and conference presentations. The PI is working with Rice K12 teacher training programs, continuing outreach to the public via blogging, and developing/presenting a lifelong learning course about the physics of materials through the cooperation of Rice’s Glasscock School for Continuing Studies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.