C$_4$N$_3$H monolayer: A novel two-dimensional organic Dirac material with high Fermi velocity

TL;DR

This paper reports the design of a new 2D organic monolayer, C$_4$N$_3$H, exhibiting high Fermi velocity and Dirac semimetal properties, which could advance applications in organic electronics.

Contribution

The study introduces a novel 2D organic Dirac material with unprecedented high Fermi velocity, expanding the potential for practical applications of organic Dirac materials.

Findings

Monolayer C$_4$N$_3$H is stable and free-standing.

It exhibits anisotropic Dirac cones with high Fermi velocity.

Fermi velocity is comparable to graphene, much higher than previous organic Dirac materials.

Abstract

Searching for two-dimensional (2D) organic Dirac materials, which have more adaptable practical applications in comparing with inorganic ones, is of great significance and has been ongoing. However, only two kinds of these materials with low Fermi velocity have been discovered so far. Herein, we report the design of an organic monolayer with C$_4$N$_3$H stoichiometry which possesses fascinating structure and good stability in its free-standing state. More importantly, we demonstrate that this monolayer is a semimetal with anisotropic Dirac cones and very high Fermi velocity. This Fermi velocity is roughly one order of magnitude larger than that in 2D organic Dirac materials ever reported, and is comparable to that in graphene. The Dirac states in this monolayer arise from the extended $\pi$-electron conjugation system formed by the overlapping 2\emph{p}$_z$ orbitals of carbon and nitrogen atoms. Our finding opens a door for searching more 2D organic Dirac materials with high Fermi velocity.