Structurally Dependent Fano Resonances in the Infrared Spectra of Phonons in Few-Layer Graphene

TL;DR

This study investigates how layer thickness and stacking order in few-layer graphene influence Fano resonances in phonon spectra, revealing strong phonon-electron coupling and stacking-dependent spectral features.

Contribution

It demonstrates the dependence of Fano resonance features on stacking order and layer number in few-layer graphene using infrared spectroscopy.

Findings

Fano resonances are observed in the infrared spectra of few-layer graphene.

Phonon intensities vary significantly with stacking order.

Strong phonon-electron coupling is evidenced by the asymmetric spectral features.

Abstract

The in-plane optical phonons around 200 meV in few-layer graphene are investigated utilizing infrared absorption spectroscopy. The phonon spectra exhibit unusual asymmetric features characteristic of Fano resonances, which depend critically on the layer thickness and stacking order of the sample. The phonon intensities in samples with rhombohedral (ABC) stacking are significantly higher than those with Bernal (AB) stacking. These observations reflect the strong coupling between phonons and interband electronic transitions in these systems and the distinctive variation in the joint density of electronic states in samples of differing thickness and stacking order.