Charge Localization and Hopping in a Topologically Engineered GNR

TL;DR

This study investigates charge localization and hopping mechanisms in topologically engineered graphene nanoribbons with alternating segments, revealing polaron formation and impaired mobility due to the system's topology.

Contribution

It introduces a two-dimensional Su-Schrieffer-Heeger model to analyze electronic properties of heterojunction GNRs with topological bands, highlighting charge transport behavior.

Findings

Charge injection leads to polaron formation in 9-AGNR segments.

Polaron mobility is significantly hindered by the system's topology.

Charge transport occurs via hopping between 9-AGNR segments.

Abstract

Graphene nanoribbons (GNRs) are promising two-dimensional materials with various technological applications, in particular for the armchair GNR families that have a semiconductor character. Recently, methods that allowed for the control of GNR's topology have been developed, resulting in the production of nanoribbons composed of alternating segments of two distinct armchair GNR families (7 and 9-AGNRs) connected in heterojunctions. This GNR displays two topological bands that lie between the valence and conduction bands that effectively modulates the nanoribbon bandgap. Here, we employ a two-dimensional extension of the Su-Schrieffer-Heeger model to study morphological and electronic properties of this new material in both neutral and charged states. Results demonstrate that charge injection in this system results in the formation of polarons that localize strictly in the 9-AGNRs segments of the system and whose mobility is highly impaired by the system's topology. We further show polaron displacement by means of hopping between 9-AGNR portions of the system, suggesting this mechanism for charge transport in this material.