Apparent corrugation variations in moir\'e patterns of dislocated graphene on Highly Oriented Pyrolytic Graphite and the origin of the van Hove singularities of the moir\'e system

TL;DR

This study investigates moiré patterns in dislocated graphene on HOPG, revealing how apparent corrugations depend on bias, and elucidates the origins of van Hove singularities in twisted bilayer graphene's electronic structure.

Contribution

It provides a combined geometric and ab initio analysis of moiré patterns, clarifying their atomic origins and electronic properties, especially regarding van Hove singularities and the graphene-like behavior of dislocated layers.

Findings

Apparent moiré corrugations vary with tunneling bias.

Different atomic arrangements can produce similar moiré periods.

Van Hove singularities originate from the band structures of twisted bilayer graphene.

Abstract

Moir\'e patterns on Highly Oriented Pyrolytic Graphite surfaces due to dislocated graphene layers were studied. We observed that the apparent corrugations of the moir\'e patterns in scanning tunnelling microscopy images change as a function of tunnel junction bias. A simple geometric investigation of the atomic structure of the graphene layers generating moir\'e patterns revealed that different atomic arrangements due to different twist angles can result in similar geometric moir\'e periods such that, only a small fraction of the observed moir\'e periodicities may coincide with the real atomic periodicity generating the moir\'e system. Ab initio calculations showed that the band structure of moir\'e patterns exhibit the fingerprints of those of bilayer graphene system preserving the Dirac cone. Moreover, our calculations in view of the correct atomistic modelling of the moir\'e patterns showed that van Hove singularities in twisted bilayer graphene system with varying angles have different origins in their respective band structures. Consequently, our results shed light on the graphene like behaviour of the top most dislocated graphene layer on HOPG surfaces by showing that the layer does not act alone but the final graphene bilayer has electronic properties partially resembling graphene.