Observation of an Electric-Field Induced Band Gap in Bilayer Graphene by Infrared Spectroscopy

TL;DR

This study experimentally demonstrates that applying a strong perpendicular electric field to bilayer graphene induces a significant band gap, confirmed by infrared spectroscopy measurements showing new optical transitions.

Contribution

First direct infrared spectroscopy observation of an electric-field-induced band gap in bilayer graphene, aligning with theoretical predictions.

Findings

Band gap up to 200 meV observed at 1 V/nm electric field

Emergence of new optical transitions indicating band gap opening

Infrared spectra consistent with tight-binding model calculations

Abstract

It has been predicted that application of a strong electric field perpendicular to the plane of bilayer graphene can induce a significant band gap. We have measured the optical conductivity of bilayer graphene with an efficient electrolyte top gate for a photon energy range of 0.2 - 0.7 eV. We see the emergence of new transitions as a band gap opens. A band gap approaching 200 meV is observed when an electric field ~ 1 V/nm is applied by an electrolyte gate to the bilayer system, inducing a carrier density of about 10^13 cm-2. The magnitude of the band gap and the features observed in the infrared conductivity spectra are broadly compatible with calculations within a tight-binding model.