Topologically localized excitons in single graphene nanoribbons

TL;DR

This study uses advanced microscopy to observe localized excitons in graphene nanoribbons, revealing how their topological features influence excitonic and vibrational properties at the atomic scale.

Contribution

It introduces a novel STM-based method to study excitons in GNRs on insulating surfaces, highlighting the role of topological end states in exciton localization.

Findings

Localized dark excitons are observed at the topological end states.

Vibronic emission features depend on GNR length, indicating confined acoustic modes.

A new approach enables atomic-scale investigation of exciton-topology interplay.

Abstract

Excitonic emission from atomically precise graphene nanoribbons (GNRs) synthesised on a metal surface is probed with atomic-scale spatial resolution using a scanning tunneling microscopy (STM) approach. A STM-based strategy to transfer the GNRs to a partially insulating surface is used to prevent light emission quenching of the ribbons by the metal substrate. Sub-nanometer resolved STM-induced fluorescence spectra reveal emission from localized dark excitons build upon the topological end states of the GNRs. A low frequency vibronic emission comb whose characteristics change with the GNR length is attributed to longitudinal acoustic modes confined to a finite box. Overall, our study provides a novel path to investigate the interplay between excitons, vibrons and topology in atomically precise graphene nanostructures.