Signature of electronic excitations in the Raman spectrum of graphene

TL;DR

This paper investigates how electronic excitations in graphene influence its Raman spectrum, highlighting the dominance of inter-band modes with specific symmetry properties and their behavior under high magnetic fields.

Contribution

It reveals the symmetry and nature of electronic excitations in graphene's Raman spectrum, especially under magnetic fields, emphasizing the role of inter-band modes and their spectral signatures.

Findings

Inter-band electronic modes dominate Raman scattering in graphene.

These modes are odd under time-inversion symmetry and belong to the A2 irreducible representation.

High magnetic fields produce inter-Landau-level modes with specific energies and polarization characteristics.

Abstract

Inelastic light scattering from Dirac-type electrons in graphene is shown to be dominated by the generation of the inter-band electronic modes which are odd in terms of time-inversion symmetry and belong to the irreducible representation A$_2$ of the point group 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 $\omega_n=2\sqrt{2n} \hbar v/\lambda_B$ and characteristically crossed polarisation of in/out photons.