@article {606,
	title = {Prediction of massless Dirac fermions in a carbon nitride covalent network},
	journal = {Appl. Phys. Lett.},
	volume = {118},
	year = {2021},
	pages = {133104},
	abstract = {Two-dimensional (2D) Dirac materials have received tremendous attention due to their potential applications in spintronics and energy applications. Motivated by recent experimental synthesis of a carbon nitride network with a C$_{2}$$_{2}$N$_{4}$ stoichiometry, the N-doped graphdiyne, or pyrazinoquinoxaline-based graphdiyne (PQ-GDY), we studied the electronic and topological properties of the PQ-GDY monolayer using first-principles calculations. Surprisingly, we found that the PQ-GDY monolayer indeed is a 2D Dirac semimetal also known as 2D topologically nontrivial semimetal. The linear band dispersions around the Dirac point are mainly composed of the bonding and antibonding pz-orbitals of C and N atoms. In combination with parity analysis, we found that the mechanism of band inversion in PQ-GDY is similar to the strain-induced Dirac cone in GDY. The underlying physical property of strained GDY is equivalent to expanding the single center benzene into the three benzene rings observed in PQ-GDY. Finally, the formed Dirac cone located on the Y-Γ high-symmetry line is very robust, and a bandgap is opened only after including a large artificial spin{\textendash}orbit coupling, which transforms it to a 2D topological insulator.},
	doi = {10.1063/5.0046069},
	author = {Jiangming Cao and Zhi-Quan Huang and Gennevieve M. Macam and Yifan Gao and Naga Venkateswara Rao Nulakani and Xun Ge and Xiang Ye and Feng-Chuan Chuang and Li Huang}
}