Nano Lett. 15, 1547 (2015)
Many-body effects resulting from strong electron–electron and electron–phonon interactions play a significant role in graphene physics. We report on their manifestation in low B field magneto-phonon resonances in high-quality exfoliated single-layer and bilayer graphene encapsulated in hexagonal boron nitride. These resonances allow us to extract characteristic effective Fermi velocities, as high as 1.20 × 10⁶ m/s, for the observed “dressed” Landau level transitions, as well as the broadening of the resonances, which increases with the Landau level index.