Distinguishing Coulomb and electron-phonon interactions for massless Dirac fermions

TL;DR

This paper presents a method to distinguish electron-electron and electron-phonon interactions in graphene by analyzing spectral functions and employing maximum entropy inversion, revealing detailed insights into inelastic scattering processes.

Contribution

It introduces a technique to separately extract electron-electron and electron-phonon spectral densities from spectral data in graphene.

Findings

Distinct incoherent sidebands identify EE and EP interactions.

Maximum entropy inversion effectively separates the two interaction types.

The method offers new insights into inelastic scattering in graphene.

Abstract

While many physical properties of graphene can be understood qualitatively on the basis of bare Dirac bands, there is specific evidence that electron-electron (EE) and electron-phonon (EP) interactions can also play an important role. We discuss strategies for extracting separate images of the EE and EP interactions as they present themselves in the electron spectral density and related self-energies. While for momentum, $k$, equal to its Fermi value, $k_F$, a composite structure is obtained which can be difficult to separate into its two constituent parts, at smaller values of $k$ the spectral function shows distinct incoherent sidebands on the left and right of the main quasiparticle line. These image respectively the EE and EP interactions, each being most prominent in its own energy window. We employ a maximum entropy inversion technique on the self energy to reveal the electron-phonon spectral density separate from the excitation spectrum due to coulomb correlations. Our calculations show that this technique can provide important new insights into inelastic scattering processes in graphene.