Ab initioGWplus cumulant calculation for isolated band systems: Application to organic conductor(TMTSF)2PF6and transition-metal oxideSrVO3

Abstract

We present ab initio $GW$ plus cumulant-expansion calculations for an organic compound ${(\mathrm{TMTSF})}_{2}{\mathrm{PF}}_{6}$ and a transition-metal oxide ${\mathrm{SrVO}}_{3}$. 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.