Infrared spectroscopy of electronic bands in bilayer graphene

TL;DR

This study uses infrared spectroscopy to analyze the electronic band structure of bilayer graphene under different doping levels, revealing key spectral features and discrepancies with theoretical predictions.

Contribution

It provides detailed experimental spectra of bilayer graphene and compares them with tight binding calculations, highlighting new insights into band parameters and electron-hole asymmetry.

Findings

Identification of interband transition features in spectra

Observation of gate voltage dependence and electron-hole asymmetry

Discrepancy between experimental and theoretical bandgap-related structures

Abstract

We present infrared spectra (0.1-1 eV) of electrostatically gated bilayer graphene as a function of doping and compare it with tight binding calculations. All major spectral features corresponding to the expected interband transitions are identified in the spectra: a strong peak due to transitions between parallel split-off bands and two onset-like features due to transitions between valence and conduction bands. A strong gate voltage dependence of these structures and a significant electron-hole asymmetry is observed that we use to extract several band parameters. Surprisingly, the structures related to the gate-induced bandgap are much less pronounced in the experiment than predicted by the tight binding model.