Cumulant expansion for phonon contributions to the electron spectral function

Abstract

We describe an approach for calculations of phonon contributions to the electron spectral function, including both quasiparticle properties and satellites. The method is based on a cumulant expansion for the retarded one-electron Green's function and a many-pole model for the electron self-energy. The electron-phonon couplings are calculated from the Eliashberg functions, and the phonon density of states is obtained from a Lanczos representation of the phonon Green's function. Our calculations incorporate ab initio dynamical matrices and electron-phonon couplings from the density functional theory code ABINIT. Illustrative results are presented for several elemental metals and for Einstein and Debye models with a range of coupling constants. These are compared with experiment and other theoretical models. Estimates of corrections to Migdal's theorem are obtained by comparing with leading order contributions to the self-energy, and are found to be significant only for large electron-phonon couplings at low temperatures.

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• Ab initio electron-phonon interactions in correlated electron systems
• Theoretical Understanding of Photon Spectroscopies in Correlated Materials In and Out of Equilibrium
• Next-to-Leading Order Ab Initio Electron-Phonon Scattering
• Influence of Fröhlich polaron coupling on renormalized electron bands in polar semiconductors. Results for zincblende GaN
• Finite temperature Green's function approach for excited state and thermodynamic properties of cool to warm dense matter
• Particle-hole cumulant approach for inelastic losses in x-ray spectra
• Intermediate Polaronic Charge Transport in Organic Crystals from a Many-Body First-Principles Approach
• Demonstration of resonant inelastic X-ray scattering as a probe of exciton-phonon coupling
• Quasi-particles ultrafastly releasing kink bosons to form Fermi arcs in a cuprate superconductor
• From carriers and virtual excitons to exciton populations: Insights into time-resolved ARPES spectra from an exactly solvable model
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• Low temperature-semiconductor band gap thermal shifts: T^4 shifts from ordinary acoustic and T^2 from piezoacoustic coupling
• Non-perturbative Green's function method to determine the electronic spectral function due to electron-phonon interactions: Application to a graphene model from weak to strong coupling
• Manifestations of the electron-phonon interaction range in angle resolved photoemission spectra
• Nonperturbative self-consistent electron-phonon spectral functions and transport
• Many-body calculations of plasmon and phonon satellites in angle-resolved photoelectron spectra using the cumulant expansion approach
• Beyond-quasiparticle transport with vertex correction: self-consistent ladder formalism for electron-phonon interactions
• Applicability of the cumulant expansion method for the calculation of transport properties in electron-phonon systems
• Many-body Green's function approaches to the doped Fröhlich solid: Exact solutions and anomalous mass enhancement