Multiple topological phase transitions in noncentrosymmetric Ga2BiAs

Based on first-principles calculations combined with symmetry analyses, we theoretically investigate the topological phase transitions in noncentrosymmetric compound ${\mathrm{Ga}}_{2}\mathrm{BiAs}$. Without spin-orbital coupling (SOC), ${\mathrm{Ga}}_{2}\mathrm{BiAs}$ is a topological semimetal with a pair of triple degenerate points located in the ${k}_{z}$ axis of the Brillouin zone. When SOC is included, the triple degenerate points evolve into Dirac points due to the protection of crystal symmetry. To understand the constraints of crystal symmetry on degenerate points, the $\mathbit{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbit{p}$ effective models are constructed. Furthermore, we demonstrate the topological translations of ${\mathrm{Ga}}_{2}\mathrm{BiAs}$ from the Dirac semimetal phase to the topological insulator and Weyl semimetal phases through the selective breaking of symmetry. Our work not only reveals the bulk-boundary correspondence of ${\mathrm{Ga}}_{2}\mathrm{BiAs}$ but also promotes the study of topological phase transitions.