  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.
