▎ 摘　　要

The resonance between the G-band phonon excitation and Landau level optical transitions in graphene has been systematically studied by micromagneto Raman mapping. In purely decoupled graphene regions on a graphite substrate, eight traces of anticrossing spectral features with G-mode peaks are observed as a function of magnetic fields up to 9 T, and these traces correspond to either symmetric or asymmetric Landau level transitions. Three distinct split peaks of the G mode, named G(-), G(i), and G(+), are observed at the strong magnetophonon resonance condition corresponding to a magnetic field of similar to 4.65 T. These three special modes are attributed to (i) the coupling between the G phonon and the magneto-optical transitions, which is responsible for G(+) and G(-) and can be well described by the two coupled mode model and (ii) the magnetic field-dependent oscillation of the G(i) band, which is currently explained by the G band of graphite modified by the interaction with G(+) and G(-). The pronounced interaction between Dirac fermions and phonons demonstrates a dramatically small Landau level width (similar to 1.3 meV), which is a signature of the ultrahigh quality graphene obtained on the surface of graphite.