Moir\'e edge states in twisted graphene nanoribbons

TL;DR

This paper reveals that twisted graphene bilayers support a new class of moiré edge states that are robust, energy-specific, and modulated by the moiré pattern, differing from traditional edge states.

Contribution

It demonstrates the existence of moiré edge states in twisted graphene bilayers, which are robust across edge types and depend on lattice commensuration rather than just twist angle.

Findings

Moiré edge states exist for all edge geometries.

These states occur at energies related to van Hove singularities.

They are strongly modulated by the moiré lattice pattern.

Abstract

The edge physics of graphene based systems is well known to be highly sensitive to the atomic structure at the boundary, with localized zero mode edge states found only on the zigzag type termination of the lattice. Here we demonstrate that the graphene twist bilayer supports an additional class of edge states, that (i) are found for all edge geometries and thus are robust against edge roughness, (ii) occur at energies coinciding with twist induced van Hove singularities in the bulk and (iii) possess an electron density strongly modulated by the moir\'e lattice. Interestingly, these "moir\'e edge states" exist only for certain lattice commensurations and thus the edge physics of the twist bilayer is, in dramatic contrast to that of the bulk, not uniquely determined by the twist angle.