Effect of a magnetic field on the two-phonon Raman scattering in graphene
Résumé
We have studied, both experimentally and theoretically, the change of the so-called $2D$ band of the Raman scattering spectrum of graphene (the two-phonon peak near 2700~cm$^{-1}$) in an external magnetic field applied perpendicular to the graphene crystal plane at liquid helium temperature. A shift to lower frequency and broadening of this band is observed as the magnetic field is increased from 0 to 33~T. At fields up to 5--10~T the changes are quadratic in the field while they become linear at higher magnetic fields. This effect is explained by the curving of the quasiclassical trajectories of the photo-excited electrons and holes in the magnetic field, which enables us (i)~to extract the electron inelastic scattering rate, and (ii)~to conclude that electronic scattering accounts for about half of the measured width of the $2D$~peak.
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