Comment on the "Create Dirac Cones in Your Favorite Materials", by Chia-Hui Lin and Wei Ku (arXiv:1303.4822)

TL;DR

This comment discusses how Dirac points can be engineered in materials via symmetry arguments, clarifying the mechanisms proposed by Lin and Ku for inducing Dirac cones through impurity-induced CDW states.

Contribution

It provides a symmetry-based explanation for the emergence of Dirac points in materials engineered with impurities, complementing Lin and Ku's original proposal.

Findings

Dirac points can be explained by symmetry considerations.

Impurities induce a charge density wave that leads to Dirac cones.

Symmetry analysis clarifies the conditions for Dirac point emergence.

Abstract

Recently a paper by Lin and Ku \cite{lin} was posted, where the authors propose a very interesting idea to engineer the Dirac points in material which originally did not have such points by inducing a CDW state through introduction of impurities like vacancy, substitution, or intercalation. In this comment we would like to explain the appearance of the Dirac points in such engineered structures by symmetry arguments.