Concomitant enhancement of electron-phonon coupling and electron-electron interaction in graphene decorated with ytterbium

The presence of foreign atoms induces exotic many-body physics in a condensed matter system. Especially, a two-dimensional system is very sensitive to such an external perturbation to lead metal-insulator transition, Kondo effect, strongly enhanced electron-phonon coupling, etc. Here we report that the presence of Yb results in the enhancement of not only electron-phonon coupling, but also electron-electron interaction in graphene. When the band structure of graphene with Yb exhibits the characteristics of electron-phonon coupling that is not clearly observed in as-grown graphene, the slope of the energy-momentum dispersion was also found to decrease by the presence of Yb using angle-resolved photoemission spectroscopy. Within the Fermi liquid theory, the decreased slope indicates enhanced electron-electron interaction, suggesting possibility interplay between electron-phonon coupling and electron-electron interaction in graphene decorated with foreign atoms.