Magnetophonon resonance and electron-phonon coupling in twisted bilayer graphene

We use electronic Raman scattering at magnetic fields up to 9T to investigate the electron-phonon coupling in bilayer graphene with a relative twist between the two layers greater than the magic angle. We take advantage of the enhanced scattering at wavelengths resonant with the bright interlayer exciton state to detect electronic transitions between Landau levels in the Raman spectrum. We extract information on the electron-phonon coupling from observation of a splitting in the graphene Raman G band due to an avoided crossing where the phonon energy matches a Landau level transition. By applying an external gate voltage, we tune the occupation factor of the Landau levels and track the evolution of the magnetophonon resonance with helicity-resolved scattering.