Correlated Topological States in Graphene Nanoribbon Heterostructures

TL;DR

This paper reveals how electron correlation effects significantly influence topological in-gap states in graphene nanoribbon heterostructures, leading to magnetic and energy renormalization phenomena consistent with experimental observations.

Contribution

It demonstrates the importance of correlation effects in GNR heterostructures, showing their impact on magnetic moments and energy splitting of topological states, a factor not considered in previous models.

Findings

Correlation effects increase magnetic moments at edges.

Energy renormalization of topological end states observed.

Discovery of a novel mechanism causing energy splitting.

Abstract

Finite graphene nanoribbon (GNR) heterostructures host intriguing topological in-gap states (Rizzo, D. J. et al.~\textit{Nature} \textbf{2018}, \textit{560}, 204]). These states may be localized either at the bulk edges, or at the ends of the structure. Here we show that correlation effects (not included in previous density functional simulations) play a key role in these systems: they result in increased magnetic moments at the ribbon edges accompanied by a significant energy renormalization of the topological end states -- even in the presence of a metallic substrate. Our computed results are in excellent agreement with the experiments. Furthermore, we discover a striking, novel mechanism that causes an energy splitting of the non-zero-energy topological end states for a weakly screened system. We predict that similar effects should be observable in other GNR heterostructures as well.