Theoretical prediction of HfB₂ monolayer, a two-dimensional Dirac cone material with remarkable Fermi velocity

Abstract

Searching for new two-dimensional (2D) Dirac cone materials has been popular since the discovery of graphene with a Dirac cone structure. Based on density functional theory (DFT) calculations, we theoretically designed a HfB₂ monolayer as a new 2D Dirac material by introducing the transition metal Hf into a graphene-like boron framework. This newly predicted HfB₂ monolayer has pronounced thermal and kinetic stabilities along with a Dirac cone with a massless Dirac fermion and Fermi velocities (3.59 × 10⁵ and 6.15 × 10⁵ m s^-1) comparable to that of graphene (8.2 × 10⁵ m s^-1). This study enriches the diversity and promotes the application of 2D Dirac cone materials.