Electronic correlations and dynamical screening with ab initio quantum embedding

TL;DR

This paper introduces a fully self-consistent $GW$+EDMFT method combining nonlocal effects and local correlations, enabling accurate ab initio descriptions of strongly correlated materials like SrMnO$_3$ and LaNiO$_3$.

Contribution

The authors develop an efficient, fully self-consistent $GW$+EDMFT implementation with a controlled double-counting scheme and ISDF compression, improving the description of screening in correlated materials.

Findings

Resolves overscreening issues in constrained-RPA approaches.

Achieves a Mott-insulating state in SrMnO$_3$ consistent with experiments.

Provides a predictive ab initio framework for strongly correlated materials.

Abstract

First-principles descriptions of correlated quantum materials require a simultaneous treatment of strong local many-body effects and nonlocal dynamical screening. We present an efficient fully self-consistent implementation of $GW$+EDMFT that combines nonlocal effects at the $GW$ level with a non-perturbative treatment of local correlations within extended dynamical mean-field theory (EDMFT), while providing a controlled double-counting prescription. Crucially, self-consistency in both the Green's function and the dynamically screened interaction is essential to achieve a consistent description of screening processes across energy scales. The efficient computation of this self-consistent solution is enabled here by compressing two-particle correlation functions using interpolative separable density fitting (ISDF). Applying the scheme to the Mott insulator SrMnO$_3$ and the correlated metal LaNiO$_3$, we show that full self-consistency resolves the overscreening inherent to constrained-RPA approaches. By suppressing spurious low-energy screening channels, a Mott-insulating state in quantitative agreement with experiment is obtained for SrMnO$_3$. These results establish fully self-consistent $GW$+EDMFT as a predictive ab initio framework for strongly correlated quantum materials.