Weyl semimetal phases and intrinsic spin-Hall conductivity in SbAs ordered alloys

Using density functional theory calculations, we investigated possible Weyl semimetal (WSM) phases in antimony arsenide ordered alloys ${\mathrm{Sb}}_{1\ensuremath{-}x}{\mathrm{As}}_{x}$ ($x=0,1/6,1/3,1/2,2/3,5/6,1$). We find WSM phases for all As compositions of ${\mathrm{Sb}}_{1\ensuremath{-}x}{\mathrm{As}}_{x}$ with broken inversion symmetry, in contrast to ${\mathrm{Bi}}_{1\ensuremath{-}x}{\mathrm{Sb}}_{x}$ where only compositions $x=1/2$ and $5/6$ were predicted to exhibit WSM phases. The WSM phases in ${\mathrm{Sb}}_{1\ensuremath{-}x}{\mathrm{As}}_{x}$ are characterized by the presence of 12 Weyl points, located within 55 meV from the Fermi level in the case of $x=1/2$. The robust spin-orbit coupling strength and Berry curvature in these alloys produce large spin-Hall conductivity in the range of 176--602 ($\ensuremath{\hbar}/e$)(S/cm), comparable to that in the BiSb alloys. Finally, ${\mathrm{Sb}}_{0.5}{\mathrm{As}}_{0.5}$ is predicted to be almost lattice matched to GaAs(111), with the Fermi level within the gap of the semiconductor, facilitating growth and characterization, and thus, offering promising integration with conventional semiconductors.