Bi_1−xAs_x alloys as Topological Weyl semimetals

Weyl semimetal (WSM) phase in bismuth arsenic alloys (Bi_1−xAs_x) are investigated using density functional theory, varying the atomic composition and position arrangement. We find three WSM states with As concentration of x =0.5, 0.67 and 0.83 with specific inversion symmetry broken structures. The Weyl points are located very close to Fermi level in all three compositions, facilitating their observation in experiments, and also suggests that they could be characterized by analyzing surface and bulk transport properties. The presence of Fermi arc verifies the Weyl semimetal phase in the 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 that surface bands reside within the bulk band gap. Our results depict the importance of composition and structure arrangement in determining the Weyl semimetal phases in the Bi_1−xAs_x alloys.