Engineering magnetic edge states in zigzag graphene nanoribbons

Zigzag graphene nanoribbons (ZGNRs) are expected to host electronic edge states that are ferromagnetically coupled along the long axis of the ribbon and antiferromagnetically coupled across the width of the ribbon. This unique electronic structure however is often obscured by the innate chemical reactivity of spin-ordered edge states. An unusually strong hybridization on ZGNRs with accessible surface states of the underlying support represents a veritable challenge to their exploration. We describe the bottom-up synthesis of ZGNRs featuring a superlattice of heteroatom dopants along the zigzag edge. Using scanning tunneling spectroscopy (STS), we demonstrate that the substitutional doping of ZGNRs with nitrogen atoms leads to a partial localization of the valence and conduction band edge states and an overall contraction of the quasiparticle band gap. Experimental results reveal that the magnetic edge states of nitrogen doped ZGNRs can readily be decoupled from the metallic growth substrate using a simple tip manipulation protocol. Our work suggests a new strategy to chemically passivate the reactive edges of ZGNRs without sacrificing the emergent spin degree of freedom critical to the exploration and realization of graphene-based spintronics.