Two-dimensional ZrB2C2 with multiple tunable Dirac states

Abstract

In this paper, we designed a two-dimensional honeycomb monolayer ZrB₂C₂, which is predicted to be a stable nanosheet and exhibits favorable mechanical and thermal properties. The Young's modulus of ZrB₂C₂ is 122.3 N m⁻¹, which is about one third of that of graphene. The ab initio molecular dynamics (AIMD) results show that ZrB₂C₂ can sustain up to 500 K. In addition, ZrB₂C₂ is semi-metallic and it exhibits twelve Dirac cones in the first Brillouin zone; the six pairs of Dirac cones form compensated electron–hole pockets, and the maximum Fermi velocity is about 6.3 × 10⁵ m s⁻¹, which is about 60% of that of graphene. Compared with other transition metal borides which possess Dirac states, the twelve Dirac cones are all robust under different types of external strains, and the Dirac states could be shifted along the opposite direction crossing the Fermi energy barrier by external strains and the gap of the two Dirac cones could be opened around the Fermi energy level with the effect of spin–orbit coupling.