Graphyne: Hexagonal network of carbon with versatile Dirac cones

TL;DR

This paper investigates alpha, beta, and gamma graphyne, revealing their versatile Dirac cones caused by carbon triple bonds, which influence electronic properties and potential applications in carbon-based nanostructures.

Contribution

It demonstrates how carbon triple bonds in different graphyne allotropes create unique Dirac cone features and affect electronic structures, expanding understanding of 2D carbon materials.

Findings

Dirac cones with reversed chirality in alpha graphyne

Momentum shift of Dirac point in beta graphyne

Switch of energy gap in gamma graphyne

Abstract

We study alpha, beta, and gamma graphyne, a class of graphene allotropes with carbon triple bonds, using a first-principles density-functional method and tight-binding calculation. We find that graphyne has versatile Dirac cones and it is due to remarkable roles of the carbon triple bonds in electronic and atomic structures. The carbon triple bonds modulate effective hopping matrix elements and reverse their signs, resulting in Dirac cones with reversed chirality in alpha graphyne, momentum shift of the Dirac point in beta graphyne, and switch of the energy gap in gamma graphyne. Furthermore, the triple bonds provide chemisorption sites of adatoms which can break sublattice symmetry while preserving planar sp2-bonding networks. These features of graphyne open new possibilities for electronic applications of carbon-based two-dimensional materials and derived nanostructures.