We propose that the Dirac cone electronic states can be generally realized in those hexagonal perovskite bilayers sliced out directly from their cubic bulk phases. This is based on the simple analyses that the A-site atoms of these perovskites contribute neither valence nor conduction electrons and after the quasi-atom simplification their hexagonal bilayers indeed possess the honeycomb symmetry. Taking the CsPbBr$_3$ (111) bilayer as an example, with the density functional theory (DFT) calculations, we demonstrate their Dirac cones around the Fermi level and find the corresponding Fermi velocity, $sim$ 2$times$10$^6$m/s, can be almost twice as large as that of graphene. While under ambient conditions the solid ionic compounds normally do not conduct charge carriers very well, such high-velocity ballistic carrier transport in the new layered Dirac materials may revitalize the conventional perovskites and thereby bring new ultra-fast ionic electronics.
Published in: "arXiv Material Science".