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Dennis P. Clougherty
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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.
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