Elusive electron-phonon coupling in quantitative analyses of the spectral function

Abstract

We examine multiple techniques for extracting information from ARPES data, and test them against simulated spectral functions for electron-phonon coupling. We find that, in the low-coupling regime, it is possible to extract self-energy and bare-band parameters through a self-consistent Kramers-Kronig bare-band fitting routine and verify the momentum independence of the self-energy along the quasiparticle dispersion. We also show that the effective coupling parameters deduced from the renormalization of quasiparticle mass, velocity, and spectral weight are momentum dependent and, in general, distinct from the true microscopic coupling; the latter is thus not readily accessible in the quasiparticle dispersion revealed by ARPES.