Composition and Stacking Dependent Topology in Bilayers from the Graphene Family

We investigate from first-principles the electronic and structural properties of silicene, germanene, and stanene bilayers. Due to the staggering of the individual layers, several stacking patterns are possible, most of which are not available to the bilayer graphene. Our results reveal the appearance of distinct band features, including orbital hybridization and band inversion, and they are attributed to the combined effects of the composition, stacking, and to the presence of the spin-orbit coupling. It is found that particular arrangements give rise to topological features in the Hall response, offering new directions for exploring Dirac features in 2D systems.