Determination of the gate-tunable bandgap and tight-binding parameters in bilayer graphene using infrared spectroscopy

TL;DR

This study uses infrared spectroscopy and a tight-binding model to demonstrate and quantify a gate-tunable bandgap in bilayer graphene, providing detailed parameters and insights into interaction effects.

Contribution

It presents the first comprehensive determination of tight-binding parameters and the gate-dependent bandgap in bilayer graphene through combined experimental and theoretical analysis.

Findings

Successful fitting of infrared spectra with tight-binding model

Quantitative determination of the gate-dependent bandgap

Identification of interaction effects causing model-data mismatches

Abstract

We present a compelling evidence for the opening of a bandgap in exfoliated bottom-gated bilayer graphene by fitting the gate-voltage modulated infrared reflectivity spectra in a large range of doping levels with a tight-binding model and the Kubo formula. A close quantitative agreement between the experimental and calculated spectra is achieved, allowing us to determine self-consistently the full set of Slonczewski-Weiss-McClure tight-binding parameters together with the gate-voltage dependent bandgap. The doping dependence of the bandgap shows a good agreement with the existing calculations that take the effects of self-screening into account. We also identify certain mismatches between the tight-binding model and the data, which can be related to electron-electron and electron-phonon interactions.