Nodal adsorbate bound states in armchair graphene nanoribbons: Fano resonances and adsorbate recognition in weak disorder

Abstract

We consider adsorbates on metallic armchair-graphene nanoribbons (AGNRs). An adsorbed atom on a nodal site of the gapless subband in the AGNR is found to induce a bound state. The nodal-adsorbate bound state alone does not cause reflection in the AGNR quantum transport in the one propagating-channel regime. Yet its manifestation, as a Fano resonance in G, is brought forth by the presence of a non-nodal adsorbate (or a scatterer) located on a longitudinally separated site. Both the adsorbate-dependent nature and the significantly enhanced energy resolution of the Fano structure in G invite adsorbate recognition. The Fano peak is shown to be robust against weak disorder such as from edge vacancies, due to the localized nature of the Fano resonant state. Adsorbates F and OH, described within an extended Huckel model, are considered as examples.