Fano resonance in Raman scattering of graphene

TL;DR

This paper investigates Fano resonances in the Raman G band of single-layer graphene, revealing doping-dependent asymmetric line shapes linked to phonon-exciton interactions, and contrasting behavior in bilayer graphene.

Contribution

It demonstrates the doping dependence of Fano resonances in single-layer graphene and explains their absence in bilayer graphene within an excitonic interaction framework.

Findings

Fano resonance appears in SLG near charge neutrality point

Fano resonance is absent in bilayer graphene regardless of doping

Interference between phonons and excitonic spectra explains the observations

Abstract

Fano resonances and their strong doping dependence are observed in Raman scattering of single-layer graphene (SLG). As the Fermi level is varied by a back-gate bias, the Raman G band of SLG exhibits an asymmetric line shape near the charge neutrality point as a manifestation of a Fano resonance, whereas the line shape is symmetric when the graphene sample is electron or hole doped. However, the G band of bilayer graphene (BLG) does not exhibit any Fano resonance regardless of doping. The observed Fano resonance can be interpreted as interferences between the phonon and excitonic many-body spectra in SLG. The absence of a Fano resonance in the Raman G band of BLG can be explained in the same framework since excitonic interactions are not expected in BLG.