The GW plus cumulant method and plasmonic polarons: application to the homogeneous electron gas

Abstract

We study the spectral function of the homogeneous electron gas using many-body perturbation theory and the cumulant expansion. We compute the angle-resolved spectral function based on the GW approximation and the `GW plus cumulant' approach. In agreement with previous studies, the GW spectral function exhibits a spurious plasmaron peak at energies 1.5${\omega }_{\mathrm{pl}}$ below the quasiparticle peak, ${\omega }_{\mathrm{pl}}$ being the plasma energy. The GW plus cumulant approach, on the other hand, reduces significantly the intensity of the plasmon-induced spectral features and renormalizes their energy relative to the quasiparticle energy to ${\omega }_{\mathrm{pl}}$. Consistently with previous work on semiconductors, our results show that the HEG is characterized by the emergence of plasmonic polaron bands, that is, broadened replica of the quasiparticle bands, red-shifted by the plasmon energy.

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• Low-energy peak in the one-particle spectral function of the electron gas at metallic densities
• Elucidating Many-Body Effects in Molecular Core Spectra through Real-Time Approaches: Efficient Classical Approximations and a Quantum Perspective
• Many-body Green's function approaches to the doped Fröhlich solid: Exact solutions and anomalous mass enhancement