Discovery and control of high-Z materials - Beyond Mott and topological materials

人们普遍认为谁控制了材料谁就控制了技术。新兴技术越来越需要新的单晶材料，以确定基本性质的研究，并成功地将其性质集成到最先进的器件结构中。由相互竞争的基本相互作用驱动的大量量子材料尚未被探索和理解。PI试图发现、合成和研究的正是这些量子材料。美国在科学和技术方面的领导地位要求大幅增加拥有新材料合成和表征技能的科学家人数。当前的形势是一个紧迫的国家挑战，如果不加以解决，最终可能会破坏国家的经济竞争力。该项目通过为研究生和本科生提供严格的培训来解决这一问题，这些学生是推动经济发展的技术的未来人力资本。技术描述新颖的量子材料可以表现出令人惊讶的甚至革命性的物理性质，这是科学和技术关键进步所必需的。该项目重点研究具有强自旋轨道相互作用的强相关材料，这些相互作用表现为强量子效应，可以由非常弱的外部刺激诱导。最近的研究表明，该项目解决了高z材料特有的以下四个主题：(1)量子态的电流控制。结构和物理特性的电流控制是科学技术长期追求但难以实现的目标。PI最近的工作表明，扭曲莫特绝缘体中的强自旋轨道相互作用足以实现这一重要目标。(2)非受挫三聚体晶格中的精细量子液体：Ba3n+1Ir3nO9n+1 （n=1,2，）。量子自旋液体是最受关注的物质状态之一。虽然理论上可以预测，但它们还没有被实验观察到。PI的初步工作揭示了三聚体晶格Ba4Ir3O10中异常强烈的挫折，以及Ir3O12三聚体在产生自旋纠缠中的关键作用。PI最近合成的三聚体系列Ba3n+1Ir3nO9n+1单晶将为寻找新的物质相提供新的范例。(3)无磁极化的环流驱动巨磁电阻：磁极化通常会降低几乎所有材料中的电子散射和电阻，是巨磁电阻的重要组成部分。PI最近发现的Mn3Si2Te6和Ca3Ru2O7是这个规则的令人惊讶的例外。电阻率下降高达9个数量级，但只有在避免磁极化的情况下，这意味着一种新型的电输运尚未被探索。(4)新量子材料的发现与合成。成功地发现新现象需要对新材料的不懈追求，这一直是PI研究的重要组成部分。晶体合成工作将集中在具有类似自旋轨道相互作用和电子相关性的材料上。要研究的现象打破常规，具有深远的科学和技术突破。该项目结合了成熟的专业知识、全面的实验设施和广泛的合作，补充了内部研究。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 DESCRIPTIONIt is widely recognized that whoever controls materials controls technology. Emerging technologies increasingly require new single-crystal materials for definitive studies of fundamental properties, and successful integration of their properties into state-of-art device structures. A large number of quantum materials that are driven by competing fundamental interactions have yet to be explored and understood. It is these quantum materials that the PI seeks to discover, synthesize, and study. U.S. leadership in Science and Technology requires drastically increasing the number of scientists who possess skills in both the synthesis and characterization of new materials. The current situation presents an urgent national challenge that could ultimately undermine the Nation’s economic competitiveness, if left unaddressed. This project addresses this problem by providing rigorous training of graduate and undergraduate students, who are the future human capital for technologies that drive the economy.TECHNICAL DESCRIPTIONNovel quantum materials can exhibit surprising or even revolutionary physical properties necessary for critical advances in science and technology. This project focuses on strongly correlated materials with strong spin-orbit interactions that are manifested in strong quantum effects that can be induced by surprisingly weak external stimuli. Recent research dictates the project address the following four topics unique to the high-Z materials: (1) Electric-current control of quantum states. Electric-current control of structural and physical properties is a long-sought but elusive goal of science and technology. The PI’s recent work demonstrates that strong spin-orbit interactions in a distorted Mott insulator is sufficient to realize this important goal. (2) Delicate quantum liquid in un-frustrated trimer lattices and beyond: Ba3n+1Ir3nO9n+1 (n=1,2,). Quantum spin liquids are among the most intensively sought states of matter. Although theoretically predicted, they have not been experimentally observed. PI’s preliminary work revealed an anomalously strong frustration in the trimer lattice Ba4Ir3O10, and a critical role of Ir3O12 trimers in producing spin entanglement. Single crystals of the trimer series Ba3n+1Ir3nO9n+1 the PI has recently synthesized will provide a new paradigm in the search for novel phases of matter. (3) Loop-current-driven colossal magnetoresistance without magnetic polarization: Magnetic polarization usually reduces electron scattering and electrical resistance in almost all materials and is an essential ingredient of colossal magnetoresistance. The PI most recently discovered Mn3Si2Te6 and Ca3Ru2O7 are surprising exceptions to this rule. The electrical resistivity drops by up to 9 orders of magnitude, but only when the magnetic polarization is avoided, implicating a new type of electrical transport yet to be explored. (4) Discovery and synthesis of new quantum materials. A successful effort to discover novel phenomena requires a persistent pursuit of new materials, which has been an essential part of the PI’s research. The crystal synthesis effort will focus on materials with comparable spin-orbit interactions and electron correlations. The phenomena to be studied defy conventional precedents and pose far-reaching scientific and technological breakthroughs. The project brings to bear combined assets of proven expertise, comprehensive experimental facilities, and broad collaborations that complement in-house research.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.