Angle-resolved photoemission spectroscopy reveals pronounced kinks in the dispersion of the $\sigma$ band of graphene. Such kinks are usually caused by the combination of a strong electron-boson interaction and the cutoff in the Fermi-Dirac distribution. They are therefore not expected for the $\sigma$ band of graphene that has a binding energy of more than $\approx 3.5\mathrm{eV}$. We argue that the observed kinks are indeed caused by the electron-phonon interaction, but the role of the Fermi-Dirac distribution cutoff is assumed by a cutoff in the density of $\sigma$ states. The existence of the effect suggests a very weak coupling of holes in the $\sigma$ band not only to the $\pi$ electrons of graphene but also to the substrate electronic states. This is confirmed by the presence of such kinks for graphene on several different substrates that all show a strong coupling constant of $\lambda \approx 1$.

• Received 26 May 2013
• Corrected 22 November 2013

DOI:https://doi.org/10.1103/PhysRevLett.111.216806