Sb_1−xAs_x and Bi_1−xAs_x alloys as Topological Weyl semimetals

Weyl semimetal (WSM) phase in antimony arsenic Sb_1-xAs_x alloys and bismuth arsenic Bi_1-xAs_x alloys are investigated using density functional theory, varying atomic composition, and structure arrangements. We find WSM states in all As concentrations in SbAs alloys, and for three As concentrations (x=0.5, 0.67, and x=0.83) in BiAs alloys with specific inversion symmetry broken. The Weyl points are located very close to the Fermi level in all compositions, facilitating their observation in experiments and suggesting that they could be characterized by analyzing surface and bulk transport properties. The presence of Fermi arcs also verifies the Weyl semimetal phase in SbAs and BiAs alloys. There is a total of 12 Weyl points located in the Brillouin zone for each composition. The chirality of these points shows that 6 Weyl points are the source and 6 Weyl points are the sink of Berry curvature. Our calculations also show that the surface bands reside within the bulk band gap. Our results illustrate the importance of composition and structure arrangement for determining the Weyl semi-metal phase in the Sb_1-xAs_x and Bi_1-xAs_x alloys.