Metallic graphene nanoribbons with tunable bandwidth and magnetic properties*

It is known that 7-armchair graphene nanoribbon(AGNR) holds topological end states at its zigzag ends. A superlattice with such end states is predicted to give rise to in-gap bands whose energies differ from the bulk states’ significantly, which will form a well-isolated subspace. Utilizing these characters of the topological states, we develop a novel AGNR superlattice that possesses two zigzag edges per unit cell. We further show using first principle calculations that, by modifying the geometry of such GNRs, it is possible to get metallic GNRs with tunable bandwidth. Explicitly, the occurrence of five-membered rings would change the bandwidth drastically. After including substrate effects, we reach good agreement with experimental results. In addition, we predict that one of the structures would have ferrimagnetic orders based on Lieb’s theorem and confirmed by density functional theory (DFT) calculation.