Self-consistent cumulant expansion for the electron gas.

Holm B., Aryasetiawan F.

Lund Univ Dept Theoret Phys Solvegatan 14a S-22362 Lund Sweden
Max Planck Inst Festkorperforsch D-70569 Stuttgart Germany

Until recently, calculations of one-electron Green functions within the GW approximation have been performed without self-consistency. Recent self-consistent GW calculations for the electron gas suggest that vertex corrections are important in a self-consistent scheme. While the GW approximation gives good description for the quasiparticles, its description for the satellite structure is less satisfactory. Significant improvement for the satellite structure can be obtained using the cumulant expansion. To study the effects of self-consistency within the cumulant expansion, we have performed self-consistent calculations for the electron gas. Multiple plasmon satellites are obtained as in the non-self-consistent calculations and the effects of self-consistency on the satellite energies turned out to be small, suggesting small vertex corrections for the satellite energies within a self-consistent cumulant expansion scheme. The satellite intensity, on the other hand, is modified. The resulting self-consistent Green function has the same characteristic,features of a self-consistent GW for the quasiparticle part, but now with a significantly improved plasmon satellite structure, which is more realistic.

Physical Review B, 56 12825-12831, 1997.

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