CAREER: Emergent Quantum Spin-Liquid in Yb-Pyrochlores and Yb-Spinels

在著名的凝聚态奇异相中，最近引起人们特别关注的是量子自旋液体（qsl）。人们普遍认为，极端的量子纠缠和几何挫折导致了qsl的定义性质：强自旋相关，没有静态磁矩，以及不间断的晶体对称性。尽管对QSL的研究非常深入，但对QSL状态对各种扰动（如化学压力、位点紊乱和额外磁相互作用）的响应尚未进行深入研究。此外，QSL研究的一个主要障碍是缺乏实例。该奖项支持了一种实验方法，用于研究Yb3+离子的局部结构变化与不同yb -焦绿石中QSL态的扰动效应和各种yb尖晶石的奇异磁性之间的相关性。在这两种情况下，几何挫折角共享四面体Yb3+网络强烈影响其磁性能。研究者将合成和生长新的钇辉绿石和钇尖晶石晶体，并研究两个重要的物理方面：(1)利用交流磁化率测量和中子散射研究它们的磁基态性质；（ii）利用对分布函数技术得到Yb3+磁性离子的局部结构变化。该项目将培养两名研究生；旨在吸引本科生和高中生，特别是少数民族学生，以激励和接触真实的科学和技术世界。这将与田纳西大学的教育高级计划（EAP）和田纳西路易斯斯托克斯少数民族参与联盟（TLSAMP）计划合作实现。研究者还将提供晶体和提供服务，培训学生晶体生长和晶体加工到更广泛的科学界。摘要对量子物质物理性质的认识一直是现代凝聚态物理研究的前沿。最近的一个例子是量子自旋液体（QSLs）：一种具有强自旋相关性但没有静态磁序的独特状态。磁性原子的几何排列使它们无法控制自己的磁矩，材料在磁性上受到阻碍。qsl的奇异性质只在极低的温度下出现，并且预计对各种扰动敏感。此外，QSL研究的一个主要障碍是缺乏实例。本项目将探索新的QSL材料，并研究微扰对它们的影响。QSL候选材料的单晶将在研究者的实验室中生长，然后在低温和强磁场下通过各种方法进行研究。该项目将培养两名研究生；旨在吸引本科生和高中生，特别是少数民族学生，激励他们接触真实的科学和技术世界。这将与田纳西大学的教育高级计划（EAP）和田纳西路易斯斯托克斯少数民族参与联盟（TLSAMP）计划合作实现。研究者还将提供晶体和提供服务，培训学生晶体生长和晶体加工到更广泛的科学界。

Technical AbstractAmongst the celebrated exotic phases of condensed matter, of particular recent interest are the quantum spin liquids (QSLs). It is widely believed that extreme quantum entanglement and geometrical frustration lead to QSLs' defining properties: strong spin correlations, the absence of static magnetic moments, and unbroken crystalline symmetry. Despite the intensive studies on QSLs, the response of the QSL state to various perturbations, such as chemical pressure, site disorder, and extra magnetic interactions, has not been thoroughly studied. Moreover, one main obstacle for QSL studies is the shortage of the examples. This award supports an experimental approach for studying the correlations between the local structural variations of the Yb3+ ions and both the perturbation effects on the QSL state in different Yb-pyrochlores and the exotic magnetism of various Yb-spinels. In both cases the geometrically frustrated corner-shared tetrahedral Yb3+-network strongly influences their magnetic properties. The investigator will synthesize, and grow crystals of new Yb-pyrochlores and new Yb-spinels and study two important physical aspects: (i) the nature of their magnetic ground states by using AC susceptibility measurements and neutron scattering; (ii) the local structural variations of the Yb3+ magnetic ions by using the pair distribution function technique. The program will train two graduate students; and aims to attract undergraduate and high school students, particularly minority students, to motivate and expose to the real world of science and technology. This will be acheived in collaboration with the Educational Advanced Program (EAP) and the Tennessee Louis Stokes Alliance for Minority Participation (TLSAMP) program at the University of Tennessee. The investigator will also provide crystals and offer services for training students on crystal growth and crystal processing to a broader scientific community.Non-Technical AbstractThe understandings of the physical properties of quantum matters have been at the forefront of modern condensed matter physics research. One recent example is quantum spin liquids (QSLs): a unique state with strong spin correlations but without static magnetic order. The geometrical arrangements of the magnetic atoms prevent them to direct their magnetic moment, the materials are magnetically frustrated. The exotic properties of QSLs appear only at extremely low temperatures, and are expected to be sensitive to various perturbations. Moreover, one main obstacle for QSL studies is the shortage of examples. This program will explore new QSL materials and study the perturbation effects on them. Single crystals of the QSL candidates will be grown in the investigator's laboratory and then will be studied by various methods under low temperatures and high magnetic fields. The program will train two graduate students; and aims to attract undergraduate and high school students, particularly minority students, to motivate and expose them to the real world of science and technology. This will be acheived in collaboration with the Educational Advanced Program (EAP) and the Tennessee Louis Stokes Alliance for Minority Participation (TLSAMP) program at the University of Tennessee. The investigator will also provide crystals and offer services for training students on crystal growth and crystal processing to a broader scientific community.