Band gap and broken chirality in single-layer and bilayer graphene

TL;DR

This review discusses how breaking inversion symmetry in single- and bilayer graphene opens a band gap, affecting chirality and pseudospin, with experimental evidence from Fabry-Perot interference measurements.

Contribution

It provides a comprehensive overview of the effects of symmetry breaking on band structure and chirality in graphene, supported by experimental observations.

Findings

Band gap opening at the K-point due to inversion symmetry breaking

Alteration of pseudospin and chirality near the band gap

Experimental evidence from Fabry-Perot interference in bilayer graphene

Abstract

Chirality is one of the key features governing the electronic properties of single- and bilayer graphene: the basics of this concept and its consequences on transport are presented in this review. By breaking the inversion symmetry, a band gap can be opened in the band structures of both systems at the K-point. This leads to interesting consequences for the pseudospin and, therefore, for the chirality. These consequences can be accessed by investigating the evolution of the Berry phase in such systems. Experimental observations of Fabry-Perot interference in a dual-gated bilayer graphene device are finally presented and are used to illustrate the role played by the band gap on the evolution of the pseudospin. The presented results can be attributed to the breaking of the chirality in the energy range close to the gap.