Magnetic Resonance Study of Novel Phases and Dynamics in the Strongly Correlated Spin-Orbit Coupled Materials

非技术摘要：为信息、传感和能源技术的高级应用寻找具有可控期望性质的新材料的技术驱动力，需要理解量子物质的新形式。量子材料研究中的一个中心问题是研究强电子相互作用与局部自旋纠缠(电子的磁矩)和轨道自由度(即所谓的自旋-轨道耦合)的综合效应。预测出射性质是一个巨大的理论问题，因为自旋轨道纠缠的存在意味着自旋受到其绕原子核轨道的影响，因此电子的自旋没有很好的定义。现有的理论提出了大量奇异量子相的出现，可以通过局域电荷/轨道或局域自旋性质来区分。该奖项支持使用局部微观测量对这些新出现的相进行广泛研究，旨在同时探测自旋、电荷/轨道和晶格属性。这项研究的变革性目标是找到一个合适的理论框架来描述具有强相关性和SOC的系统，从而促进具有设计性质的材料的发现。布朗大学和国家高磁场实验室的研究人员同时探测磁性和轨道/电荷性质，同时将样品置于外加磁场中，并改变电子荷量，以调整相互竞争的相互作用。通过为参与科学、建模和技术开发的研究生和本科生建立一个具有挑战性的培训场地，该项目嵌入了强大的教育成分。国家强磁场实验室和其他国际用户设施的工作将对学生的培训特别有益。技术摘要：本研究计划重点是利用核磁共振技术对具有不同自旋轨道耦合(SOC)量的强关联电子系统的涌现顺序进行实验研究，目的是破译导致物质涌现量子态的不同相互作用之间的复杂相互作用。这些核磁共振测量被设计为在相关的低能量尺度上同时探测自旋、电荷/轨道和晶格自由度(DOF)，以便对这些涌现相进行广泛的研究。最初的重点是双钙钛矿材料，用有限四极矩原子核的核磁共振研究。通过将这些发现与低能准粒子的动力学效应相关联，可以推断出轨道和磁态的微观性质。此外，还进行了实验数据与理论模型(和模拟)的比较，以全面了解自旋、晶格、电荷和轨道自由度如何在复合材料中合作、竞争和/或重构，以产生新的现象和/或磁态。具体到所述目标，竞争相互作用由外部参数调节，例如磁场，以及化学压力、电荷掺杂和SOC强度的协调变化。为了实现这些目标，研究小组正在开发一种新的核磁共振方法，该方法基于量子信息科学(QIS)的核磁共振概念，以解开自旋和轨道的自由度，并测量自旋和电荷通道中单独的线性响应。这项研究被扩展到拓扑近藤绝缘体，以提供对强关联、SOC、多轨道和多价自由度相互作用所产生的本征性质的一般理解。该研究项目的变革性目标是帮助确定一个适当的理论框架来描述这样的系统，其中相关性和SOC具有类似的能量规模，并且两者都不能被微扰处理。这一奖项反映了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 Abstract: The technological drive to find new materials with controllable desired properties for advance applications in information, sensing, and energy technologies, requires understanding of the new forms of quantum matter. A central issue in quantum materials research is study of the combined effects of strong electronic interactions with local entanglement of spin (the magnetic moment of electron) and orbital degrees of freedom, so-called spin-orbit coupling. Predicting emergent properties represents a huge theoretical problem since the presence of the spin orbit entanglement implies that the spin is affected by its orbiting an atomic nucleus, and therefore the spin of an electron is not well defined. Existing theories propose the emergence of a multitude of exotic quantum phases, distinguishable by either local charge/orbital or local spin properties. This award supports research on extensive study of these emergent phases using local microscopic measurements, designed to concurrently probe spin, charge/orbital, and lattice properties. The transformative goal of this research is to identify an appropriate theoretical framework for describing systems with both strong correlations and SOC and so promote the discovery of materials with designed properties. The researchers at Brown University and National High Magnetic Field Laboratory simultaneously probe magnetic and orbital/charge properties while subjecting the samples to applied magnetic field and varying the amount of electronic charge, to tune competing interactions. A strong educational component is imbedded in the project by establishing a challenging training ground for students, both graduate and undergraduate, who will be involved in the scientific, modeling, and technical developments. The work at the National High Magnetic Field Laboratory and other international user facilities will be of particular benefit in training students.Technical Abstract: This research program focuses on the experimental investigation of emergent orders in strongly correlated electron systems with varying amount of spin-orbit coupling (SOC) using nuclear magnetic resonance (NMR) techniques with the goal to decipher the complex interplay between different interactions that leads to the emergent quantum states of matter. These NMR measurements are designed to concurrently probe spin, charge/orbital, and lattice degrees of freedom (DOF) at the relevant low energy scales for an extensive study of these emergent phases. Initial emphasis is on double-perovskites materials, investigated by NMR on nuclei with finite quadrupolar moment. The microscopic nature of orbital and magnetic states is inferred by correlating these findings with the dynamical effects associated with low energy quasiparticles. Furthermore, the comparison of experimental data to theoretical models (and simulations) is carried out, in order to build a comprehensive understanding of the ways in which the spin, lattice, charge, and orbital DOF cooperate, compete, and/or reconstruct in complex materials to produce novel phenomena and/or magnetic states. Specific to the stated goals, the competing interactions are tuned by external parameters, such as magnetic field, and coordinated variations in chemical pressure, charge doping, and strength of SOC. To achieve these objectives, the research team is developing a novel NMR approach based on the use of NMR concepts from quantum information science (QIS) to untangle spin and orbital degrees of freedom, and measure separate linear response in the spin and charge channels. The study is extended to topological Kondo insulators to provide a general understanding of intrinsic properties arising from the interplay of strong correlations, SOC, multi-orbital, and multi-valence DOF. The transformative goal of the research project is to help identify an appropriate theoretical framework for describing systems in which correlations and SOC are of comparable energy scale and neither can be treated perturbatively.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.