Realistic effective interactions from the functional renormalization group

一个广泛使用的方法，在固体中的电子相关效应是基于低能量有效模型（LEEM），专注于费米能级附近的频带的推导。LEEM的参数由包含所有材料特定信息的高能问题确定。在这里，我们的目标是通过使用功能重整化群（fRG）为基础的计划，在LEEM的改进建设。整合出高能量的问题，导致重正化的有效相互作用，是相关的从头计算描述与预测能力。特别是，fRG方法考虑到屏蔽和其他重整化的裸库仑相互作用在Wannier投影通过重新计算的所有通道的贡献在平等的基础上。这种扩展相对于在一个选定的通道中的受约束的迭代允许一个获得不同的筛选通道，它们的相互作用和它们的频率结构的更完整的图片。有效相互作用参数的相应变化会对低能物理产生重要影响。我们计划应用和测试的fRG的有效相互作用的纳米系统和异质结构的非均匀系统。在这些部分之后，后续目标是将fRG有效交互方案与从头算软件包（如WIEN2K或VASP）联系起来。与子项目P02、P03和P07的密切联系允许与ViCoM中使用的其他理论工具进行比较，并评估LEEM的fRG结构对低能前端（P03和P15）的影响。

A widely-used approach to electronic correlation effects in solids is based on the derivation of low-energy effective models (LEEM) that focus on the bands near the Fermi level. The parameters of the LEEM are determined by the high-energy problem that contains all the materials specific information. We here aim at an improved construction of the LEEM by using a functional renormalization group (fRG) based scheme. Integrating out the high-energy problem leads to renormalizations of the effective interactions that are relevant for an ab-initio description with predictive power. In particular, the fRG approach takes into account the screening and other renormalizations of the bare Coulomb interactions in the Wannier projection by resumming the contributions of all channels on equal footing. This extension with respect to constrained resummations in a selected channel allows one to obtain a more complete picture of the different screening channels, their interplay and their frequency structure. The corresponding changes on the effective interaction parameters can have an important impact on the low-energy physics. We plan to apply and test the fRG for the effective interactions to nanosystems and inhomogeneous systems as heterostructures. After these parts, a subsequent goal is to link fRG effective interaction schemes to ab-initio software packages (like WIEN2K or VASP). The close contact to subprojects P02, P03 and P07 allows to compare to other theoretical tools used in ViCoM and to assess the effects of the fRG construction of the LEEM on the low-energy frontend (P03 and P15).