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

TL;DR

This paper investigates the challenges of accurately extracting electron-phonon coupling information from ARPES spectral data, highlighting the limitations of common analysis methods and the momentum dependence of effective coupling parameters.

Contribution

The study systematically tests extraction techniques against simulated data, revealing the elusive nature of true microscopic electron-phonon coupling in ARPES analysis.

Findings

Self-consistent Kramers-Kronig fitting can recover parameters in low-coupling regimes.

Effective coupling parameters are momentum dependent and differ from true microscopic coupling.

True electron-phonon coupling is difficult to access directly from ARPES quasiparticle dispersion.

Abstract

We examine multiple techniques for extracting information from angle-resolved photoemission spectroscopy (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. 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.