Theoretical Solid State Physics

非技术描述：该项目支持凝聚态物理和材料科学的理论和计算研究及教育。凝聚态物质的迷人性质和现象源于构成这种物质的电子和离子的相互作用，其中许多离子是现代技术的核心，如电子学、光电子学和能量转换设备。通常，由于改变化学成分或将材料限制在纳米尺度上，这些性质会发生显着变化或出现新的现象。这个项目的中心是使用量子理论、建模和模拟来解释和预测新材料和纳米结构。新的理论方法和现代大规模并行计算机的可用性使该团队能够获得原子薄材料、纳米结构、界面和缺陷现象、新超导体和光催化材料的行为的第一性原理(即没有经验参数)的解释和预测。教育部分的重点是培训研究生和博士后研究员，以便在当前的技术革命中使用材料进行研究和开发。研究成果发表在科学期刊上，并在该团队的网站上公布。从该项目开发的计算工具被整合到几个软件包中--Berkeley GW、PARATEC和EPW--这些软件包可以在网上免费提供给研究界。另一项教育活动与公众教育有关，这是通过在非专业媒体上发表的文章和采访以及通过公开演讲来完成的。技术描述：该项目旨在通过进行第一原理量子计算，在微观水平上了解材料和纳米结构的电子和光学性质。研究的主题包括：二维(2D)晶体，如石墨烯和过渡金属二卤化物；纳米管和纳米带；新型块体(如拓扑绝缘体)和降维系统的电子性质和光物理；以及超导。重点放在使用现实的模型，与实验者的密切合作，对新的和有用的材料的调查和预测，以及新的理论和计算方法的发展。采用了几种不同的方法。采用从头算赝势方法和总能量技术，在密度泛函理论框架下计算基态性质。用基于准粒子激发的GW近似的第一原理自能方法和基于光激发的Bethe-Salpeter方程的从头算相互作用两粒子格林函数方法研究了激发态(光谱)现象。其他研究依赖于分子动力学和蒙特卡罗模拟、介电函数方法、BCS理论和标准多体理论的扩展。对现有方法的增强也被用来处理强电子关联。

Nontechnical Description: This project supports theoretical and computational research and education on condensed matter physics and materials science. The fascinating properties and phenomena of condensed matter emerge from mutual interactions of the electrons and ions that constitute the material, many of which are central to modern technologies such as electronics, optoelectronics, and energy conversion devices. Often these properties are dramatically altered or new phenomena emerge from varying the chemical composition or confining the materials to nanometer scales. This project is centered on using quantum theory, modeling, and simulations to explain and predict novel materials and nanostructures. New theoretical approaches and the availability of modern massively parallel computers allow the team to obtain first-principles (i.e., with no empirical parameters) explanations and predictions of the behavior of atomically thin materials, nanostructures, interfacial and defect phenomena, new superconductors, and photocatalytic materials. The educational components are focused on training of graduate students and postdoctoral fellows for research and development in using materials in the current technological revolution. The research findings are published in scientific journals as well as presented on the team's website. The computational tools developed from the project are incorporated into several software packages - Berkeley GW, PARATEC, and EPW - 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.Technical Description: This project aims at understanding the electronic and optical properties of materials and nanostructures at the microscopic level by performing first-principles quantum calculations. Topics investigated include: two-dimensional (2D) crystals such as graphene and transition metal dichalcogenides; nanotubes and nanoribbons; electronic properties and photophysics of novel bulk (such as topological insulators) and reduced-dimensional systems; and superconductivity. Emphasis is placed on using realistic models, close collaborations with experimentalists, investigations and predictions of novel and useful materials, and development of new theoretical and computational approaches. Several different approaches are employed. The ab-initio pseudopotential method and total-energy techniques are applied within the density functional formalism to compute ground-state properties. Excited-state (spectroscopic) phenomena are investigated using a first-principle self-energy approach based on the GW approximation for quasiparticle excitations and an ab-initio interacting two-particle Green's function method based on the Bethe-Salpeter equation for optical excitations. Other studies rely on molecular dynamics and Monte Carlo simulations, dielectric function methods, BCS theory, and extensions of standard many-body theory. Augmentation of existing methods to deal with strong electron correlations is also employed.