Topologically localized excitons in single graphene nanoribbons

Intrinsic optoelectronic properties of atomically precise graphene nanoribbons (GNRs) remain largely unexplored because of luminescence quenching effects that are due to the metallic substrate on which the ribbons are grown. We probed excitonic emission from GNRs synthesized on a metal surface with atomic-scale spatial resolution. A scanning tunneling microscope (STM)-based method to transfer the GNRs to a partially insulating surface was used to prevent luminescence quenching of the ribbons. STM-induced fluorescence spectra reveal emission from localized dark excitons that are associated with the topological end states of the GNRs. A low-frequency vibronic emission comb is observed and attributed to longitudinal acoustic modes that are confined to a finite box. Our study provides a path to investigate the interplay between excitons, vibrons, and topology in graphene nanostructures.

Automated summary

In this study, the intrinsic optoelectronic properties of graphene nanoribbons (GNRs) were explored using a scanning tunneling microscope-based method. By transferring the GNRs onto a partially insulating surface, luminescence quenching effects were prevented and localized dark excitons associated with the topological end states of the GNRs were observed.