Probing enhanced electron-phonon coupling in graphene by infrared resonance Raman spectroscopy

TL;DR

This study uses infrared resonance Raman spectroscopy to reveal a significant enhancement of electron-phonon coupling in graphene near the Dirac point, impacting transport modeling in graphene-based devices.

Contribution

It demonstrates an increased electron-phonon interaction in graphene at low energies, supported by experimental measurements and ab initio calculations, highlighting a momentum-dependent coupling.

Findings

Giant increase in 2D/2D' peak intensity ratio near the Dirac point

Enhanced, momentum-dependent electron-phonon coupling in graphene

Implications for modeling transport in graphene devices at room temperature

Abstract

We report on resonance Raman spectroscopy measurements with excitation photon energy down to 1.16 eV on graphene, to study how low-energy carriers interact with lattice vibrations. Thanks to the excitation energy close to the Dirac point at $\mathbf{K}$, we unveil a giant increase of the intensity ratio between the double-resonant 2D and 2D$^\prime$ peaks with respect to that measured in graphite. Comparing with fully \textit{ab initio} theoretical calculations, we conclude that the observation is explained by an enhanced, momentum-dependent coupling between electrons and Brillouin zone-boundary optical phonons. This finding applies to two dimensional Dirac systems and has important consequences for the modeling of transport in graphene devices operating at room temperature.