CAREER: Correlated excited states of point defects in insulators

该奖项支持旨在了解材料局部缺陷（称为“点缺陷”）特性的计算研究和教育活动，例如原子从其通常位置缺失或材料中的杂质。这种点缺陷在所有材料中都是普遍存在的，即使是极少量的缺陷也会对材料的性能产生深远的影响。在电子设备中，点缺陷可能是有害的，例如，降低太阳能电池的效率；或者是功能性的，例如，允许调整材料的特性。缺陷本身甚至可以用作下一代量子计算机的微小量子比特。点缺陷的小而稀的性质使它们成为实验表征的挑战，因此计算模拟是至关重要的。然而，传统的计算方法对关键缺陷特性的准确性有限，包括对光或电脉冲等外部刺激的响应。目前存在精度更高的先进理论，但需要太多的计算能力才能应用于点缺陷。该项目旨在开发和利用计算工具，通过“嵌入”来克服这些问题，即将传统方法与先进理论相结合，以获得计算效率和准确性。这些新技术将使PI和他的团队对由外部刺激激发的复杂缺陷有前所未有的理解。PI将应用这些嵌入方法来探索各种有希望用于下一代电子设备（包括量子计算机）的缺陷和宿主材料。该奖项还支持各级计算物理教育的发展。在研究生阶段，将开设一门专门针对教授计算凝聚态物理中最先进方法的课程；在本科阶段，物理专业所需的计算物理课程将会改变，使其更加互动和以项目为基础；在高中阶段，将开展外展活动，以提高计算机素养。该奖项支持旨在理解点缺陷的激发态物理的研究和教育活动。PI将开发量子嵌入技术，结合密度泛函理论和多体方法，以准确捕获电子器件和量子技术相关缺陷中的电子相关性和激发。旨在改进方法的项目将开发更精确和稳健的处理缺陷轨道之间的库仑相互作用，缺陷和体态之间的杂化，以及将密度泛函理论与多体方法相结合所固有的重复计数。将与基于量子蒙特卡罗的其他多体方法进行比较，以对嵌入过程中涉及的各种近似进行基准测试。此外，PI将关注涉及缺陷和晶格之间相互作用的问题，以确定相关激发态在缺陷的光学和非辐射过程中的作用。特定缺陷/宿主系统的目标将包括六方BN中的碳基缺陷，iii族氮化物中的过渡金属和过渡金属二硫族化物中的稀土，所有这些都是传统和量子电子设备的基础和技术兴趣。该奖项还支持各级计算物理教育的发展。在研究生阶段，将开设一门专门针对教授计算凝聚态物理中最先进方法的课程；在本科阶段，物理专业所需的计算物理课程将会改变，使其更加互动和以项目为基础；在高中阶段，将开展外展活动，以提高计算机素养。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。

NONTECHNICAL SUMMARYThis award supports computational research and education activities that aim to understand the properties of localized imperfections in materials, called "point defects", such as atoms missing from their usual locations or impurities within the material. Such point defects are ubiquitous in all materials and can have profound effects on their properties even if present in minute quantities. In the context of electronic devices, point defects may be detrimental, e.g., lowering the efficiency of solar cells; or functional, e.g., allowing the properties of materials to be tuned. Defects themselves can even be used as tiny quantum bits for next generation quantum computers. The small and dilute nature of point defects makes them a challenge for experimental characterization, thus computational simulations are vital. However, conventional computational methods have limited accuracy for key defect properties including their response to external stimuli like light or electrical pulses. More advanced theories with significantly better accuracy exist but require too much computational power to be applied to point defects. This project seeks to develop and utilize computational tools that overcome these issues via “embedding,” i.e., by combining the conventional methods with the advanced theories to obtain both computational efficiency and accuracy. These new techniques will allow the PI and his team to develop unprecedented understanding of complex defects excited by external stimuli. The PI will apply these embedding methods to explore a variety of defects and host materials that are promising for the next generation electrical devices including quantum computers.This award also supports the development of computational physics education at all levels. At the graduate level, a course specifically aimed at teaching state-of-the-art methods in computational condensed-matter physics will be developed; at the undergrad level, the computational physics class required for physics majors will be altered to make it more interactive and project-based; and at the high-school level, outreach will be conducted to improve computational literacy.TECHNICAL SUMMARYThis award supports research and educational activities that aim to understand the physics of excited electronic states of point defects. The PI will develop quantum embedding techniques for combining density-functional theory and many-body methods to accurately capture electron correlations and excitations in defects relevant for electronic devices and quantum technologies. Projects aimed at methodological improvements will develop more accurate and robust treatments of Coulomb interactions between defect orbitals, hybridization between the defect and bulk states, and the double-counting intrinsic to combining density-functional theory with many-body methods. Comparisons with other many-body methods based on quantum Monte Carlo will be performed to benchmark the various approximations involved in the embedding procedure. In addition, the PI will focus on problems involving interplay between the defect and the crystal lattice to determine the role of correlated excited states in optical and nonradiative processes at defects. The specific defect/host systems targeted will include carbon-based defects in hexagonal BN, transition metals in group-III nitrides, and rare earths in transition-metal dichalcogenides, all of which are of fundamental as well as technological interest for conventional and quantum electronic devices.This award also supports the development of computational physics education at all levels. At the graduate level, a course specifically aimed at teaching state-of-the-art methods in computational condensed-matter physics will be developed; at the undergrad level, the computational physics class required for physics majors will be altered to make it more interactive and project-based; and at the high-school level, outreach will be conducted to improve computational literacy.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.