Environmental Breakdown of Topological Interface States in Armchair Graphene Nanoribbon Heterostructures

Abstract

We theoretically investigate the stability and transport properties of topological interface states (IFs) in 9-7-9 and 15-13-15 armchair graphene nanoribbon heterostructures (AGNRHs) laterally embedded in boron nitride (BN) sheets. Two configurations, $n$-BNNR/AGNRH/$n$-BNNR and $n$-BNNR/AGNRH/$n$-NBNR, corresponding to same-topology and reverse-topology BN environments, are examined within a tight-binding framework. Using a bulk boundary perturbation approach, we show that in BNNR/AGNRH/BNNR the IFs are destroyed by chirality breaking induced by symmetric BN environments at both interfaces. In contrast, the IFs in the reverse-topology structure remain robust against lateral interface interactions from BN atoms. Transport calculations further demonstrate that the surviving IFs in BNNR/AGNRH/NBNR exhibit the characteristic behavior of topological double quantum dots, with an enhanced interdot hopping strength compared with vacuum boundary conditions. These results reveal that BN environments can either suppress or reinforce topological interface states, depending critically on the topology of the surrounding nanoribbons.