Signature of electronic excitations in the Raman spectrum of graphene

Abstract

Inelastic light scattering from Dirac-type electrons in graphene is shown to be dominated by the generation of the interband electronic modes which are odd in terms of time-inversion symmetry and belong to the irreducible representation $A_2$ of the point group ${\text{C}}_{6v}$ of the honeycomb crystal. At high magnetic fields, these electron-hole excitations appear as peculiar $n^{-}\to n^{+}$ inter-Landau-level modes with energies ${\omega }_n=2\sqrt{2n}\hslash v/{\lambda }_B$ and characteristically crossed polarization of in/out photons.