Ab initio GW plus cumulant calculation for isolated band system: Application to organic conductor (TMTSF)2PF6 and transition-metal oxide SrVO3

TL;DR

This paper applies ab initio GW plus cumulant-expansion methods to study low-energy plasmon effects on the electronic structures of an organic conductor and a transition-metal oxide, achieving better agreement with experimental photoemission spectra.

Contribution

It introduces a combined GW and cumulant-expansion approach to accurately capture low-energy plasmon effects in isolated band systems.

Findings

Low-energy plasmon fluctuations cause significant band renormalization.

Spectral weight shifts into incoherent parts, matching experimental data.

Method improves understanding of low-energy excitations in complex materials.

Abstract

We present ab initio GW plus cumulant-expansion calculations for an organic compound (TMTSF)2PF6 and a transition-metal oxide SrVO3. These materials exhibit characteristic low-energy band structures around the Fermi level, which bring about interesting low-energy properties; the low-energy bands near the Fermi level are isolated from the other bands and, in the isolated bands, unusually low-energy plasmon excitations occur. To study the effect of this low-energy-plasmon fluctuation on the electronic structure, we calculate spectral functions and photoemission spectra using the ab initio cumulant expansion of the Green's function based on the GW self-energy. We found that the low-energy plasmon fluctuation leads to an appreciable renormalization of the low-energy bands and a transfer of the spectral weight into the incoherent part, thus resulting in an agreement with experimental photoemission data.