Phonon switching and combined Fano-Rice effect in optical spectra of bilayer graphene

TL;DR

This paper presents a theoretical framework explaining the Fano-Rice effect and phonon switching in bilayer graphene's optical spectra, linking electron-phonon interactions with gate voltage and charge density variations.

Contribution

It introduces a unified model that accounts for asymmetric Fano lineshapes and phonon intensity changes, revealing a switching mechanism between phonon modes in bilayer graphene.

Findings

Identification of a phonon switching mechanism between symmetric and anti-symmetric modes.

A phase diagram showing the dependence of optical phonon response on charge density and bandgap.

Explanation of Fano lineshape asymmetry and intensity variation in optical spectra.

Abstract

Recent infrared measurements of phonon peaks in gated bilayer graphene reveal two striking signatures of electron-phonon interaction: an asymmetric Fano lineshape and a giant variation of the peak intensity as a function of the applied gate voltage. In this Letter we provide a unified theoretical framework which accounts for both these effects and unveils the occurrence of a switching mechanism between the symmetric ($E_g$) and anti-symmetric ($E_u$) phonon mode as dominant channel in the optical response. A complete phase diagram of the optical phonon response is also presented, as a function of both the charge density and the bandgap.