Spatial non-locality of electronic correlations beyond GW approximation

Area of Science:

• Condensed Matter Physics
• Quantum Chemistry
• Materials Science

Background:

• The GW approximation is a standard method for electronic structure calculations.
• Combining GW with dynamical mean-field theory (GW + DMFT) aims to improve accuracy by including strong correlation effects.
• A key assumption in practical GW + DMFT implementations is the spatial locality of diagrams beyond the GW level.

Purpose of the Study:

• To directly investigate the spatial locality of electronic correlations beyond the GW approximation.
• To assess the impact of this locality assumption on the GW + DMFT method.
• To evaluate the accuracy of vertex corrections in materials like NiO, α-Ce, and LiFeAs.

Main Methods:

• Development and application of the sc(GW + G3W2) approach.
• Performing calculations with and without the assumption of locality for higher-order diagrams (G3W2).
• Utilizing a fully momentum-dependent Green's function (G) and screened interaction (W) versus a single-site approximation.

Main Results:

• Strong spatial non-locality effects were observed in all three studied materials (NiO, α-Ce, LiFeAs).
• These non-locality effects were found to be decisive for accurate vertex corrections in NiO and LiFeAs.
• The study demonstrates that the locality assumption significantly affects the results of GW + DMFT calculations.

Conclusions:

• The assumption of spatial locality for diagrams beyond GW in GW + DMFT is questionable.
• These findings challenge the commonly accepted approximations in practical GW + DMFT implementations.
• Revisiting the locality assumption is crucial for improving the reliability of GW + DMFT for strongly correlated materials.