Stability of edge states in strained graphene

TL;DR

This paper investigates the conditions for observing stable counter-propagating edge modes in strained graphene, highlighting the role of edge type, interactions, and valley polarization effects.

Contribution

It reveals that zigzag edges support counter-propagating edge modes via a new hybridization mechanism, and analyzes how interactions and valley polarization influence their stability.

Findings

Zigzag edges support counter-propagating edge modes.

Interactions tend to destabilize these edge modes.

Spontaneous valley polarization affects edge mode stability.

Abstract

Spatially inhomogeneous strains in graphene can simulate the effects of valley-dependent magnetic fields. As demonstrated in recent experiments, the realizable magnetic fields are large enough to give rise to well-defined flat pseudo-Landau levels, potentially having counter-propagating edge modes. In the present work we address the conditions under which such edge modes are visible. We find that, whereas armchair edges do not support counter-propagating edge modes, zigzag edges do so, through a novel selective-hybridization mechanism. We then discuss effects of interactions on the stability of counter-propagating edge modes, and find that, for the experimentally relevant case of Coulomb interactions, interactions typically decrease the stability of the edge modes. Finally, we generalize our analysis to address the case of spontaneous valley polarization, which is expected to occur in charge-neutral strained graphene.