Angular momentum transport in insulators: Magnons and other emergent excitations

非技术性：在磁性绝缘体中，磁性(“自旋”)可以通过材料流动，而不会像通过电导体时产生的热量那样产生热量。这使得自旋电流对未来的低功率技术很有吸引力。在大多数磁性绝缘体中，自旋通过波传播，每个波携带一定量的磁性，但在一些材料中，自旋被认为是以更复杂的方式携带的，因此它以不同数量的分组或在时间上不同的排列方式到达，就好像磁性分组彼此捆绑在一起一样。可以使用最近开发的技术来驱动和检测自旋流。这个项目使用这些方法来研究几种这样的材料中的自旋流动作为温度和其他条件的函数，试图检验这些关于非波状自旋运动的想法。例如，自旋流动的波动可以量化每包携带的磁力量，就像波动的雨滴声音提供关于雨滴大小的信息一样。首席调查员正在与领先的理论家一起对数据进行解释。对这些系统中自旋流的基础知识对于充分实现它们在未来技术中的潜力是至关重要的，包括量子信息处理。该项目包括从莱斯和附近的少数群体服务机构招聘的两名研究生和本科生研究人员的研究和交流培训。这些人正在获得量子材料以及书面和口头沟通技能的宝贵经验，为他们进入技术劳动力做好准备。研究成果通过出版物和会议报告向科学界传播。PI正在与莱斯K12教师培训计划合作，继续通过博客向公众宣传，并通过与莱斯的Glasscock学院继续学习合作，开发/提供关于材料物理的终身学习课程。技术：通过自旋自由度的角动量传输是未来技术中信息和能量流动的另一种渠道。特别令人感兴趣的是自旋通过磁性绝缘体的传播，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子测量各种磁有序系统中的自旋输运，磁子是晶格中电子的量子化自旋波。这个项目的学术价值在于解决了基本的开放问题，包括：自旋是如何在包含奇异的新出现的自旋携带激发的材料中传输的，而不是磁子？多铁体中的自旋输运能通过耦合到电极化来控制吗？噪声在自旋输运中的基本限制是什么？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体中注入和热驱动的自旋输运。噪声技术被用来观察和量化自旋散粒噪声，自旋散粒噪声是由于自旋携带激发的离散性质而在驱动角动量输运中预测的(但尚未观察到)基本涨落。首席调查员正在与领先的理论家合作者一起对数据进行解释。自旋传播在信息技术中具有重要的应用价值，量子自旋液体在量子信息处理中具有潜在的应用价值。对这些系统中自旋传播的基础知识对于充分实现它们的潜力是必不可少的。该项目包括从莱斯和附近的少数群体服务机构招聘的两名研究生和本科生研究人员的研究和交流培训。这些人正在获得量子材料以及书面和口头沟通技能的宝贵经验，为他们进入技术劳动力做好准备。研究成果通过出版物和会议报告向科学界传播。PI正在与莱斯K12教师培训计划合作，通过博客继续向公众推广，并通过与赖斯的格拉斯考克继续学习学校的合作，开发/提供关于材料物理的终身学习课程。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.