Theoretical Solid State Physics

该奖项支持理论和计算研究和教育，目的是在微观层面上理解材料和纳米结构的电子、光学和磁性，预测新材料和现象，并为该领域的研究培养年轻科学家。凝聚态物质的迷人特性和现象来自于组成材料的电子和离子的相互作用。理解这些相互作用是现代技术的核心，如电子学、光电子学、光伏学和一般的能量转换装置。通过改变化学成分或将材料限制在纳米尺度或在一维或二维水平上探索材料，这些特性可以显著改变，并且可以出现新的现象。该项目以量子理论、建模和模拟为中心，利用分析和计算工具来解释和预测新材料和纳米结构的存在和特性。新的理论方法和现代高性能计算机的可用性使团队能够获得材料行为的第一性原理（即，没有经验参数）解释和预测，包括原子薄材料，纳米结构，界面和缺陷现象，新型超导体和光催化材料。教育部分的重点是培养学生（研究生和本科生）和博士后，为当前量子技术革命的研究和发展做好准备。该项目开发的计算工具将被整合到几个软件包中，这些软件包将在网络上免费提供给研究社区。另一项教育活动与公共教育有关，这是通过在非专业媒体上发表文章和采访以及通过PI和联合PI的公开讲座来完成的。该奖项支持理论和计算研究和教育，通过执行第一性原理量子计算，在微观水平上理解材料和纳米结构的电子、输运、光学和磁性。该研究分为凝聚态物理和材料科学的三个主题领域：1)材料的新相和结构；2)光学和自旋物理的降维系统，和3)电子-声子耦合，光-物质相互作用，和超导。主要目标是使用多体量子理论，高性能计算和新概念，如拓扑学，来解释和预测实际材料的性质和现象，包括低维系统。采用基于多体量子理论的几种最先进的方法来实现对真实材料的精确第一性原理计算。利用从头算伪势密度泛函理论的形式得到了基态性质。激发态性质由准粒子激发的GW近似内的单粒子相互作用格林函数和光学性质的Bethe-Salpeter方程中的两粒子相互作用格林函数计算。采用基于GW微扰理论的新方法计算电子-声子耦合。用另一种新开发的时变绝热GW方法计算了驱动场下的时变现象和非线性光学响应。通过上述方法可以访问许多属性。例子包括结构信息、电子结构、能隙、光学和光发射光谱、电子拓扑不变量、表面和界面特性、振动和机械特性、磁性、输运特性、泵浦探测光谱、非线性光学响应以及常规超导体的特性。理论和方法的发展也进行了进一步提高我们的概念和计算能力。在适当的时候，第一原理计算与模型哈密顿研究相结合，特别是在理解拓扑效应和具有更强电子相关性的系统时。教育部分的重点是培养学生（研究生和本科生）和博士后，以研究和开发当前的量子技术革命。该项目开发的计算工具将被整合到三个开源软件包中——Berkeley GW、PARATEC和EPW——它们在网络上免费提供给社区。另一项教育活动与公共教育有关，这是通过在非专业媒体上发表文章和采访以及通过PI和联合PI的公开讲座来完成的。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。

NONTECHNICAL SUMMARYThis award supports theoretical and computational research and education with the goals of understanding the electronic, optical, and magnetic properties of materials and nanostructures at the microscopic level, predicting new materials and phenomena, and educating young scientists for research in this field. The fascinating properties and phenomena of condensed matter emerge from mutual interactions of the electrons and ions that make up materials. Understanding these interactions are central to modern technologies such as electronics, optoelectronics, photovoltaics, and energy conversion devices in general. These properties can be dramatically altered, and new phenomena can emerge, by varying the chemical composition or confining the materials to nanometer scales or exploring materials at the one- or two-dimensional level. This project is centered on using quantum theory, modeling, and simulations using analytical and computational tools to explain and predict the existence and properties of novel materials and nanostructures. New theoretical approaches and the availability of modern high-performance computers allow the team to obtain first-principles (i.e., with no empirical parameters) explanations and predictions of the behavior of materials including atomically thin materials, nanostructures, interfacial and defect phenomena, new superconductors, and photocatalytic materials. The educational component is focused on preparing students (graduate and undergraduate) and postdoctoral fellows for research and development in the current quantum technological revolution. The computational tools developed from the project will be incorporated into several software packages, which are made freely available on the web to the research community. Another educational activity is related to public education, which is done through articles and interviews published in lay media and via public lectures by the PI and co-PI. TECHNICAL SUMMARYThis award supports theoretical and computational research and education towards understanding the electronic, transport, optical, and magnetic properties of materials and nanostructures at the microscopic level by performing first-principles quantum calculations. The research is grouped into three topical areas of condensed matter physics and materials science: 1) novel phases and structures of materials; 2) optical and spin physics of reduced-dimensional systems, and 3) electron-phonon coupling, light-matter interaction, and superconductivity. The major objective is to use many-body quantum theory, high-performance computing, and new concepts such as those from topology to explain and predict the properties of and phenomena in real materials, including lower dimensional systems. Several state-of-the-art approaches based on many-body quantum theory are employed to enable accurate first-principles calculations for real materials. Ground-state properties are obtained using the ab initio pseudopotential density functional theory formalism. Excited-state properties are calculated from the interacting one-particle Green's function within the GW approximation for quasiparticle excitations and the interacting two-particle Green's function via the Bethe-Salpeter equation for optical properties. Electron-phonon couplings are computed using a new methodology based on GW perturbation theory. Time-dependent phenomena under driven fields and nonlinear optical responses are computed using another newly developed time-dependent adiabatic GW method. A host of properties are shown to be accessible with the above methods. Examples include structural information, electronic structure, energy gaps, optical and photoemission spectra, electronic topological invariants, surface and interface characteristics, vibrational and mechanical properties, magnetic properties, transport properties, pump-probe spectroscopies, nonlinear optical responses, and properties of conventional superconductors. Theoretical and methodological developments are also carried out to further advance our conceptual and computational capabilities. The first-principles calculations are augmented with model Hamiltonian studies when appropriate, especially for understanding topological effects and systems with stronger electron correlations.The educational component is focused on training of students (graduate and undergraduate) and postdoctoral fellows for research and development in the current quantum technological revolution. The computational tools developed from the project will be incorporated into three open-source software packages - Berkeley GW, PARATEC, and EPW - which are freely available to the community on the web. Another educational activity is related to public education, which is done through articles and interviews published in lay media and via public lectures by the PI and co-PI.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.