Strain-induced metal-semimetal transition of BeB2 monolayer

Abstract

The Dirac point and cones make some two-dimensional materials (e.g., graphene, silicone and graphyne) exhibit ballistic charge transport and enormously high carrier mobilities. Here, we present a novel semimetal with triangular lattice. Metallic BeB₂ monolayer could transform to a semimetal with a Dirac point at the Fermi level when the lattice parameters are isotropically compressed by about 5%, while it becomes metallic again under larger compression. The Fermi velocity of semimetallic BeB₂ monolayer is 0.857 × 10⁶ m s⁻¹, just a little smaller than that of graphene. Furthermore, it is found that uniaxial compressive strain opens a band gap in the BeB₂ monolayer, while uniaxial tensile strain keeps it metallic. Our study expands the Dirac systems and provides new insight to explore novel semimetallic materials.