Dirac cones in two-dimensional borane

Abstract

We introduce two-dimensional borane, a single-layered material of BH stoichiometry, with promising electronic properties. We show that, according to Density Functional Theory calculations, two-dimensional borane is semimetallic, with two symmetry-related Dirac cones meeting right at the Fermi energy E_f. The curvature of the cones is lower than in graphene, thus closer to the ideal linear dispersion. Its structure, formed by a puckered trigonal boron network with hydrogen atoms connected to each boron atom, can be understood as distorted, hydrogenated borophene (Science {350}, 1513 (2015)). Chemical bonding analysis reveals the boron layer in the network being bound by delocalized four-center two-electron {\sigma} bonds. Finally, we suggest high-pressure could be a feasible route to synthesise two-dimensional borane.