Cumulant expansion for phonon contributions to the electron spectral function

S. M. Story*, J. J. Kas, F. D. Vila, M. J. Verstraete, J. J. Rehr

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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. Pole models are also used for the phonon density of states and the Eliashberg functions. Our calculations incorporate ab initio dynamical matrices and electron-phonon couplings from the density functional theory. 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 and low temperatures.

Original languageEnglish
Article number195135
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume90
Issue number19
DOIs
Publication statusPublished - 19 Nov 2014
Externally publishedYes

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