A multipole approach for dielectric screening in metallic systems

The plasmon pole (PPA) model is a popular approximation adopted for treating the frequency dependence in GW. This method has been successfully applied to a large variety of systems ranging from insulators and semiconductors, the homogeneous electron gas and simple metals like Al and Na. In contrast, metals with small plasmon energies, such as Ni, Cu and Co, are particularly challenging for simple models like in PPA, since they present strong screening effects resulting in multiple plasmonic excitations. In these cases a more accurate but computationally costly full frequency (FF) approach is usually preferred.

 

In this work we propose the use of a multipole approach (MPA) to overcome the limitations of PPA in these metals while limiting the computational cost. The proposed MPA technique has been recently developed and validated for semiconductors [1], with a particular focus on good sampling strategies in the complex frequency plane. In the present work we further extend the sampling strategies to the case of metals with small plasmon energies. We compare results of quasiparticles energies in different metallic systems computed via PPA, MPA and FF approaches.

References

[1]  D. A. Leon, et al. Phys. Rev. B 104, 115157 (2021)