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

Anastasia Varlet, Ming-Hao Liu, Dominik Bischoff, Pauline Simonet, Takashi Taniguchi, Kenji Watanabe, Klaus Richter, Thomas Ihn, Klaus Ensslin

Published 2015-08-11Version 1

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.