Discovery and study of spin-orbit-coupled quantum materials

摘要：凝聚态研究已经产生了许多具有基本性质的新型材料，这些材料支撑着许多尖端技术。现在人们普遍认为，新材料对于技术的关键进步是必要的，谁发现了新材料，谁就控制了未来的科学和技术。4d和5d过渡金属元素构成了元素周期表中d过渡金属元素的三分之二。然而，这些材料在很大程度上仍未被开发。该项目提出了一个系统的努力来发现、研究和控制4d/5d材料中的新量子态。这些材料中固有的自旋轨道和其他相互作用之间的微妙平衡为发现和控制奇异状态和物理性质提供了独特的机会。该项目还为所有参与的学生提供严格的培训，重点是合成和表征技术，涵盖广泛的材料和主要研究者实验室中可用的实验探针。技术摘要：自旋轨道相互作用驱动的物理学是当代凝聚态物理学中最重要的课题之一。这个项目是由两个相互关联的推力驱动的——发现新的量子材料和控制新的量子态。重点一：PI针对4d/5d材料的三个亚群进行单晶合成和研究：氧化物,2。S和se基硫族化合物和3。碲化。这些亚群的潜在行为预计将通过复杂结构（S或Se硫属化合物）决定的交叉机制，系统地从更相关的绝缘状态（氧化物）演变为更自旋轨道耦合的金属状态（碲化物）。这一关键趋势为有效调整相关和自旋轨道相互作用（SOI）的相对强度提供了独特的环境，从而以前所未有的方式发现/控制奇异态。推力二：SOI对4d/5d材料的物理性质表现出特别强烈和令人惊讶的影响，其中一个关键特征是SOI可以将磁矩刚性锁定在晶格上，从而导致新的行为。PI通过施加电流、静水压力或化学掺杂来研究自旋轨道耦合材料的晶格控制物理性质。电流控制的结构和物理性质是一个长期寻求，但难以实现的目标，当代科学和技术。PI最近的发现表明，强SOI和倾斜反铁磁Mott态的结合足以实现这一重要目标。国家致力于量子革命，但由于缺乏在量子材料发现和合成方面有经验的科学家，支持不足。这个项目通过严格的研究生培训来解决这个问题，强调材料的发现和合成，并为广泛的合作提供高质量的新材料晶体，这对于促进我们对正在研究的新现象的集体理解是必要的。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 Abstract: Condensed matter research has produced many novel materials with fundamental properties that underpin a remarkable number of cutting-edge technologies. It is now generally accepted that novel materials are necessary for critical advances in technologies and whoever discovers novel materials generally controls the science and technology of the future. The 4d- and 5d- transition metal elements constitute two thirds of the d-transition metal elements listed in the Periodic Table. However, these materials have remained largely unexplored. This project presents a systematic effort to discover, investigate and control novel quantum states in 4d/5d materials. A delicate balance between spin-orbit and other competing interactions inherent in these materials offers a unique range of opportunities to uncover and control exotic states and physical properties. This project also provides rigorous training to all students involved, focusing on synthesis and characterization techniques covering a broad spectrum of materials and experimental probes available in the principal investigator's laboratory. Technical Abstract: Physics driven by spin-orbit interactions is among the most important topics in contemporary condensed matter physics. This project is driven by Two Interconnected Thrusts - Discovery of New Quantum Materials and Control of Novel Quantum States. Thrust One: The PI targets three Subgroups of 4d/5d materials for single-crystal synthesis and study: 1. Oxides, 2. S- and Se-based chalcogenides and 3. Tellurides. The underlying behavior of these subgroups is expected to systematically evolve from more correlated, insulating states (oxides) to more spin-orbit-coupled, metallic states (tellurides) via a crossover regime dictated by complex structures (S or Se chalcogenides). This key trend provides unique circumstances to effectively tune the relative strength of correlations and spin-orbit interactions (SOI) in order to uncover/control exotic states in an unprecedented fashion. Thrust Two: The SOI exhibits particularly strong and surprising influence on the physical properties of the 4d/5d materials, in which a key characteristic is that the SOI can rigidly lock magnetic moments to the lattice, leading to novel behavior. The PI investigates lattice-control physical properties of spin-orbit-coupled materials via application of electrical current, hydrostatic pressure, or chemical doping. Electrical-current control of structural and physical properties is a long-sought, but elusive goal of contemporary science and technology. The PI's recent discovery demonstrates that a combination of strong SOI and a canted antiferromagnetic Mott state is sufficient to attain this important goal. The Nation is committed to a quantum revolution but is poorly supported by the lack of scientists who are experienced in quantum materials discovery and synthesis. This project is well-timed to address this problem via rigorous graduate training emphasizing materials discovery and synthesis and providing high-quality crystals of novel materials for extensive collaborations, which is necessary to advance our collective understanding of the novel phenomena under study.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.