Anomalous Ballistic Transport in Disordered Bilayer Graphene: Dimer Vacancies induced Dirac Semimetal

TL;DR

This study reveals that in disordered bilayer graphene, dimer vacancies induce an unexpected ballistic transport regime due to symmetry breaking, leading to a Dirac semimetal state with an enlarged energy window at higher impurity densities.

Contribution

It demonstrates that dimer vacancies in bilayer graphene create a ballistic transport regime and a Dirac semimetal state, a novel phenomenon not observed with non-dimer vacancies.

Findings

Dimer vacancies induce a ballistic transport regime in bilayer graphene.

Non-dimer vacancies lead to localization effects.

The energy window of ballistic transport enlarges with increased impurity density.

Abstract

We report anomalous quantum transport features in bilayer graphene in presence of a random distribution of structural vacancies. By using an efficient real-space Kubo-Greenwood transport methodology, the impact of a varying density of dimer versus non-dimer vacancies is investigated in very large scale disordered models. While non-dimer vacancies are shown to induce localization regimes, dimer vacancies result in an unexpected ballistic regime whose energy window surprisingly enlarges with increasing impurity density. Such counterintuitive phenomenon is explained by the formation of an effective linear dispersion in the bilayer bandstructure, which roots in the symmetry breaking effects driven by dimer vacancies, and provides a novel realization of Dirac semimetals in high dimension.