Ground States of Disordered Quantum Magnets

****技术摘要****提出的研究目的是为了更深入地了解无序在复杂材料中可以发挥的多方面作用。可以说，最令人兴奋和最具挑战性的体制是量子涨落发挥重要作用的体制。无序自旋二聚体化合物属于这类一般材料，至少在原则上，提供了很好的控制途径来解决感兴趣的特定问题，包括玻色玻璃行为，随机单线态形成，以及由于淬火无序而产生的有序态。拟议的研究将集中在这类材料中无序的影响上，关于这类材料的了解相对较少，人们可以希望从中收集到与更广泛的量子材料相关的重要见解。不同的化学取代可以用来在各种原型化合物中产生不同类型和强度的无序，其影响将通过测量作为化学成分函数的低温热力学性质来研究。所研究材料的单晶将在PIs实验室中生长。该奖项将支持研究生在这些领域的教育和活动。****非技术摘要****在许多具有重要技术意义的先进材料中，包括高温超导体和具有巨大磁阻的材料，这种或那种形式的无序是非常常见的。这种紊乱是一种无关的干扰，仅仅伴随着电荷掺杂，还是在确定这些材料的相关相图中起着更重要的作用，这是一个正在进行的研究和辩论的问题。考虑到这些复杂和不完全理解的材料中无序的普遍性，了解其在更简单和更好控制的模型系统中的影响是很重要的。该计划的目的是研究以前未被广泛探索的制度中的无序磁铁，其广泛目标是对广泛的量子材料中无序的影响有更深入的了解。该项目既包括低温测量，也包括广泛的晶体生长工作。这个晶体生长项目通过外部合作服务于更大的凝聚态物质社区，确保了美国凝聚态物质社区当代材料的广泛可用性，并解决了美国对材料合成的日益重视的感知需求，从而产生了更广泛的影响。该奖项将支持这些重要技术领域的研究生教育。

****Technical Abstract****The aim of the proposed research is to obtain a deeper understanding of the multifaceted roles that disorder can play in complex materials. Arguably the most exciting and challenging regimes are the ones in which quantum fluctuations play a significant role. Disordered spin dimer compounds fall in to this general class of material, providing, at least in principle, well-controlled access to specific problems of interest, including Bose glass behavior, random singlet formation, and ordered states that arise as a consequence of quenched disorder. The proposed research will focus on the effects of disorder in this class of material, about which relatively little is known, and from which one can hope to glean important insights relevant to the broader class of quantum materials. Various chemical substitutions can be used to create different types and strengths of disorder in a variety of archetypal compounds, the effects of which will be studied via measurements of the low temperature thermodynamic properties as a function of the chemical composition. Single crystals of the materials studied will be grown in the PIs laboratory. The award will support the education and activities of a graduate student in these areas. ****Non-Technical Abstract****Disorder of one form or another is remarkably common in many advanced materials of technological importance, including high-temperature superconductors and materials exhibiting colossal magnetoresistance. Whether the disorder is an irrelevant distraction, that simply accompanies, for example, charge doping, or whether it plays a more central role in determining the associated phase diagrams of these materials is a matter of ongoing research and debate. Given the prevalence of disorder in these complex and incompletely understood materials, it is important to understand its effects in simpler and better controlled model systems. It is the purpose of this program to study disordered magnets in regimes which have not previously been extensively explored, with the broad aim of developing a deeper understanding of the effects of disorder in the broad class of quantum materials. The project involves both low temperature measurements, and also an extensive crystal growth effort. This crystal growth program has a broader impact by serving the larger condensed matter community via external collaborations, ensuring the wide availability of contemporary materials for the US condensed matter community, and addressing the perceived need for increased emphasis on materials synthesis within the US. The award will support the education of a graduate student in these technologically important areas.