Correlated Topological States in Graphene Nanoribbon Heterostructures

Finite graphene nanoribbon (GNR) heterostructures host intriguing topological in-gap states localized at the edges of both the bulk and the end regions (Rizzo et al., Nature 2018, 560, 204. We employ a Green function method, which allows us to go beyond previous density functional theory simulations and show that electronic correlation effects play a key role in these systems: they result in increased magnetic moments at the ribbon edges accompanied by a significant energy renormalization of the topological end states, even in the presence of a metallic substrate -- bringing the computed features in agreement with the experiments. Furthermore, we discover a striking, novel mechanism that causes an energy splitting of non-zero topological end states for weakly screened systems. We predict that states with similar features are present in other GNR heterostructures as well.