Infrared resonance Raman of bilayer graphene: signatures of massive fermions and band structure on the 2D peak

TL;DR

This study uses low-energy resonance Raman spectroscopy to investigate massive fermions in bilayer graphene, revealing detailed band structure signatures and electron-phonon interactions through experimental and theoretical analysis.

Contribution

It provides new insights into the band structure and quasiparticle behavior of bilayer graphene at low excitation energies, combining experimental Raman data with ab initio calculations.

Findings

Clear frequency separation of 2D peak sub-structures at low excitation energy

Correlation between Raman intensity variations and electronic band splitting

Enhanced understanding of electron-phonon interactions in bilayer graphene

Abstract

Few-layer graphene possesses low-energy carriers which behave as massive fermions, exhibiting intriguing properties in both transport and light scattering experiments. Lowering the excitation energy of resonance Raman spectroscopy down to 1.17 eV we target these massive quasiparticles in the split bands close to the K point. The low excitation energy weakens some of the Raman processes which are resonant in the visible, and induces a clearer frequency-separation of the sub-structures of the resonance 2D peak in bi- and trilayer samples. We follow the excitation-energy dependence of the intensity of each sub-structure and, comparing experimental measurements on bilayer graphene with ab initio theoretical calculations, we trace back such modifications on the joint effects of probing the electronic dispersion close to the band splitting and enhancement of electron-phonon matrix elements.