Evidence for flat zero-energy bands in bilayer graphene with a periodic defect lattice.

In this work, we perform ab initio calculations, based on the density functional theory, of the electronic structure of a graphene bilayer with a periodic array of topological defects. The defects are generated by intercalation of carbon atoms between the layers and their subsequent absorption by one of the layers. We use the unit cell of the bilayer to construct larger unit cells (supercells), positioning a single carbon atom in the hollow position between the monolayers and periodically replicating the supercell. By increasing the size of the supercell and, consequently, the periodicity of the inserted atoms, we not only optimize the results but also vary the size of the defect lattice. Our main result is the appearance of a doubly degenerate flat band at the Fermi level. These states are interpreted as coming from the periodic deformation of the bilayer due to the topological defects generated by the inserted atoms. It acts as a non-Abelian flux network creating zero energy flat bands as predicted by San-Jose, González and Guinea in 2012. Since the periodic strain field associated to the defect array has such a strong influence on the electronic properties of the bilayer, it may be useful for practical applications. For instance, it can act as frozen-in magnetic-like field flux tubes. All-carbon nanostructures can then be designed to have electronic behavior at different regions tailored by the chosen defect pattern. • Ab initio test of non-Abelian flux network theoretical proposal. • Generation of periodic array of topological defects in bilayer graphene. • Zero energy degenerate flat energy bands. [ABSTRACT FROM AUTHOR]