Massively parallel simulations of strong electronic correlations: Realistic coulomb vertex and multiplet effects

强关联系统有望为不仅可以控制电荷，而且可以控制自转和轨道自由度的设备提供基础。然而，多体效应的现实描述仍然是现代凝聚态物理的重大挑战之一：基于密度泛函理论的从头计算方法和多体动力学平均场理论(LDA+DMFT方法)的结合原则上具有描述强关联材料的能力。实际上，计算仅限于轨道较少、局部库仑顶点近似的简单模型。本项目中提出的工作将朝着准确和有效地模拟强关联材料的性质迈出关键步骤：(I)优化现实哈密顿量(多体基组和屏蔽库仑顶点)的结构；(Ii)开发一个通用的(大规模并行的)LDA+DMFT框架，使用多个量子蒙特卡罗求解器来处理复杂的多体哈密顿量，包括多重态效应的逼真描述；(Iii)对一系列代表性材料(过渡金属氧化物和有机物)的系统研究，最终目标是建立一套基准相关系统的标准。

Strongly correlated systems hold the promise to provide the basis for devices in which not only charge but also spin and orbital degrees of freedom can be controlled. The realistic description of many-body effects is, however, still one of the grand-challenges of modern condensedmatter physics: The combination of ab-initio methods based on density-functional theory and the many-body dynamical mean-field theory (the LDA+DMFT method) has in principle the ability of describing strongly correlated materials. In practice, calculations are limited to simple models with few orbitals and an approximate local Coulomb vertex. The work proposed in this project will take crucial steps towards the accurate and effective simulation of the properties of strongly correlated materials: (i) optimization of the construction of realistic Hamiltonians (many-body basis set and screened Coulomb vertex); (ii) development of a general (massively parallel) LDA+DMFT framework with multiple quantum Monte Carlo solvers to deal with complex many-body Hamiltonians, including the realistic description of multiplet effects; (iii) systematic study of series of representative materials (transition-metal oxides and organics), with the ultimate goal of establishing a standard set of benchmark correlated systems.