Causal versus local $GW$+EDMFT scheme and application to the triangular-lattice extended Hubbard model

TL;DR

This paper compares two $GW$+EDMFT schemes for the triangular-lattice extended Hubbard model, finding similar results but slightly stronger correlations with the causal scheme, and applies them to spectral functions relevant for 1T-TaS2.

Contribution

It introduces and compares a causal auxiliary field $GW$+EDMFT scheme with the standard approach for the extended Hubbard model.

Findings

Both schemes produce similar results for short- and long-range interactions.

The causal scheme shows slightly stronger correlation effects at half-filling.

Spectral functions and screened interactions are computed for parameters relevant to 1T-TaS2.

Abstract

Using the triangular-lattice extended Hubbard model as a test system, we compare $GW$+EDMFT results for the recently proposed self-consistency scheme with causal auxiliary fields to those obtained from the standard implementation which identifies the impurity Green's functions with the corresponding local lattice Green's functions. Both for short-ranged and long-ranged interactions we find similar results, but the causal scheme yields slightly stronger correlation effects at half-filling. We use the two implementations of $GW$+EDMFT to compute spectral functions and dynamically screened interactions in the parameter regime relevant for 1$T$-TaS$_2$. We address the question whether or not the sample used in a recent photoemission study [Phys. Rev. Lett. 120, 166401 (2018)] was half-filled or hole-doped.