Comment on "Theory of phonon-assisted adsorption in graphene: Many-body infrared dynamics''

TL;DR

This paper critically examines the approximations used in a previous study on hydrogen adsorption on graphene, revealing that certain neglected contributions significantly alter the self-energy calculations and invalidate the single-pole approximation.

Contribution

It identifies additional contributions to the atom self-energy that challenge the validity of the approximations used in prior work on phonon-assisted adsorption.

Findings

Additional self-energy contributions are of the same order as IBMA terms.

The real part of the self-energy is significantly altered at low energies.

The single-pole approximation becomes invalid due to these contributions.

Abstract

Two approximations used by Sengupta [Phys. Rev. B {\bf 100}, 075429 (2019)] in numerically computing the adsorption rate of cold hydrogen atoms on suspended graphene are critically examined. The independent boson model approximation (IBMA) was used to compute the atom self-energy, and the single-pole approximation (SPA) was used to obtain the adsorption rate from the self-energy. It is shown explicitly that there are additional contributions to the self-energy appearing at the same order of the atom-phonon coupling as the IBMA terms that alter the value of the real part of the self-energy at low energies by several orders of magnitude in the regime of interest. This shift in the self-energy consequently renders the use of SPA invalid.