RUI: Exciton-Phonon Interactions in Solids based on Time-Dependent Density Functional Perturbation Theory

非技术总结该奖项支持计算研究和教育活动，以促进半导体和绝缘体中激发电子和晶格振动之间相互作用的理解。当一个电子被激发到一个更高的能量状态时，它会留下一个带有正电荷的空点，称为空穴。电子和空穴可以在激子状态下彼此强烈结合。声子（晶格振动的量子化）和激子之间的相互作用在许多化学和材料问题中起着至关重要的作用。本研究的目标是开发一种准确，通用，高效的第一性原理方法来计算扩展和凝聚态物质系统中的激子-声子相互作用。该方法将在能量转换和存储中有应用，范围从光电子学到光电转换器、光电探测器、光合成、光电子学、发光二极管和生物传感器。在这个项目中，PI将应用该方法研究二维货车德瓦尔斯异质结构中的激子-声子相互作用，这是新型光电和光伏器件应用的新前沿，该项目还将为本科生和研究生以及博士后学者提供前沿的教育和培训机会，他们将获得宝贵的计算材料科学经验。PI完全致力于通过加强代表性不足的群体的机会来扩大参与并增强材料研究和教育的多样性。将开设一门关于第一性原理方法的研究生课程，为学生开展研究活动做好准备。PI还将通过有针对性的招聘、研讨会、高中教师夏令营以及社区大学课程开发等方式，深入当地高中和社区大学。技术概要该奖项支持计算研究和教育活动，以开发一种新的计算方法，用于研究半导体和绝缘体中的电子激发态的耦合电子-离子动力学。理解、预测和最终控制激子行为和激子-离子耦合动力学是各种化学和材料问题的核心。精确有效的第一性原理方法是定量计算激子-声子相互作用在真实的材料中的应用的迫切需要。该项目的目标是开发一种准确，高效和强大的第一性原理方法，以基于含时密度泛函微扰理论捕获半导体和绝缘体中的激子-声子相互作用。开发的方法将允许计算的激子能带结构，电荷密度，和离子力与激子状态，激子状态之间的非绝热耦合，激子-声子耦合矩阵，激子动力学过程中扩展的固体系统。完全不受约束的非共线磁性将被实施，以确定激子性质的材料具有突出的自旋轨道耦合效应。几个层次的并行化将被利用，使计算代码服从大规模并行平台。在本计画中，此方法将被用来研究二维过渡金属二硫族化合物基货车德瓦耳斯异质结构中声子辅助的界面电荷与能量转移，揭示了激子和声子以及内部/层间激子之间的动量传递，界面激子动力学过程中的声子相互作用。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准。

NONTECHNICAL SUMMARYThis award supports computational research and educational activities to advance the understanding of interactions between excited electrons and lattice vibrations in semiconductors and insulators. When an electron is excited to a higher-energy state, it leaves an empty spot with a positive charge known as a hole. The electron and the hole can be strongly bound to each other in an excitonic state. The interactions between phonons (quantization of lattice vibrations) and excitons play a crucial role in many chemical and materials problems. The goal of this research is to develop an accurate, versatile, and efficient first-principles approach to compute exciton-phonon interactions in extended and condensed-matter systems. The method will have applications in energy conversion and storage, ranging from photovoltaics to photocatalysis, photodetectors, photo-synthesis, optoelectronics, light-emitting diodes, and biosensors. In this project, the PI will apply the method to study the exciton-phonon interactions in two-dimensional van der Waals heterostructures, which are the new frontier for novel optoelectronic and photovoltaic device applications.The project will also provide cutting-edge educational and training opportunities to undergraduate and graduate students as well as postdoctoral scholars, who will gain valuable experience in computational materials science. The PI is fully committed to broadening participation and enhancing diversity in materials research and education by strengthening opportunities for underrepresented groups. A graduate course on the first-principles method will be developed to prepare the students for the research activities. The PI will also reach out to local high schools and community colleges through targeted recruitment, workshops, summer camps for high-school teachers, and curriculum development in community colleges.TECHNICAL SUMMARYThis award supports computational research and educational activities to develop a novel computational methodology for the study of coupled electron-ion dynamics with electronic excited states in semiconductors and insulators. Understanding, predicting, and ultimately controlling exciton behavior and coupled exciton-ion dynamics are central to diverse chemical and materials problems. Accurate and efficient first-principles methods are highly desired for quantitatively computing exciton-phonon interactions in real materials applications. The project goal is to develop an accurate, efficient, and robust first-principles approach to capture exciton-phonon interactions in semiconductors and insulators based on time-dependent density functional perturbation theory. The method developed will allow calculations of the exciton band structure, charge density, and ionic forces associated with the exciton state, non-adiabatic couplings between exciton states, the exciton-phonon coupling matrix, and exciton dynamical processes in extended solid systems. Fully unconstrained noncollinear magnetism will be implemented to determine excitonic properties in materials with a prominent spin-orbital coupling effect. Several levels of parallelization will be exploited, rendering computational codes amenable to massively parallel platforms. In this project, the method will be used to study the phonon-assisted interfacial charge and energy transfer in two-dimensional transition-metal dichalcogenide-based van der Waals heterostructures, unraveling the momentum transfer between excitons and phonons as well as intra/interlayer exciton-phonon interactions during interfacial exciton dynamics.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.