BiAs as a Weyl semimetal

Bismuth belongs to the group-V in the Periodic Table, yet it is often found as a trivalent atom in compounds such as Bi2Se3 and Bi2Te3. It features a strong spin-orbit coupling, leading to non-trivial topological band structure in many Bi-containing compounds, including Bi2Se3 and LuBi. Here we explore BiAs as a novel topological material. Using density functional theory calculations and testing the various functionals, we predict the lowest energy structure of BiAs and its band structure. We find that BiAs is a trivial semimetal but at the brink of becoming a Weyl semimetal. We predict a transition at 2 GPa with band crossing along L and M/2 of the hexagonal Brillion zone, and another at 8 GPa with crossing along L and H/2 points. We find a total of 12 pairs of Weyl points including 12 nodes and 12 anti-nodes. We also predict that a ferroelectric polarization can used to tune the spintronic properties in BiAs thin films. The chirality of the Weyl points can be switched by applying external electric filed. The link between pressure and electric field can be used to alter the spin texture of the bulk BiAs system. These novel features make this material attractive for spintronic based devices.