Ab initio study of the downfolded self-energy for correlated systems: Momentum dependence and effects of dynamical screening

• The electronic structure of strongly correlated systems is usually calculated by using an effective model Hamiltonian with a small number of states and an effective on-site interaction. The mode, however, neglects the frequency dependence of the interaction, which emerges as a result of dynamical screening processes not included in the model. The self-energy calculated in this kind of model within dynamical mean-field theory (DMFT) is usually assumed to contain on-site components only. To study the validity of model calculations for the simulation of realistic materials, we make a detailed comparison between the downfolded self-energy in a model Hamiltonian with static and dynamic on-site interaction and the full ab initio self-energy for Fe and SrVO3 within the GW approximation. We find that the model GW self-energy shows weaker k (momentum) dependence than the ab initio GW self-energy, which is attributed to the lack of the long-range interaction and of contributions from other electrons not included in the models. This weak k dependence is found to lead to an artificial narrowing of the quasiparticle band structure. Moreover, this band narrowing is stronger for the dynamic (frequency-dependent) interaction, due to a larger renormalization of the quasiparticle states. These findings indicate a crucial role of the k dependence of the self-energy and dynamical screening for the electronic structure of correlated systems. We also discuss the effects beyond the GW approximation for correlated systems by comparing the GW and DMFT results.

Ämnesord

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

Publikations- och innehållstyp

art (ämneskategori)

ref (ämneskategori)