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Investigating electrons, phonons and electron-phonon interactions in graphene by Raman spectroscopy

We will first show that Resonance Raman spectroscopy is a very useful tool to investigate electrons and phonons near the Dirac point of graphenes due to the specific double resonance (DR) Raman process that occur in these materials. We have performed recent investigations of monolayer and bilayer graphene using this methodology and we were able to determine the tight-binding parameters that describe the electronic dispersions of these materials. Our results reveal a significant asymmetry between the electronic dispersion in the valence and conduction bands of bilayer graphene. The special process of electron-phonon interaction that renormalizes the phonon energy giving rise to the Kohn anomaly will be discussed, and illustrated by gated experiments where the position of the Fermi level can be changed.

coloquio-pimenta-2009