Pressure Induced topological phase transition in LaAs

Rare-earth pnictides have emerged as an important class of topological phase materials, where fundamental phenomena associated with band crossings have been predicted. Here, we use density functional theory with the Heyd, Scuseria, and Ernzerhof (HSE06) screened hybrid functional to study the band structure and the effects of spin-orbit coupling in LaAs. In DFT within the generalized gradient approximation (GGA), we find that LaAs is predicted to display a topological phase without any applied pressure due to the overestimated band overlap. The As-related p bands cross the La-related d bands near the X point. Such crossing does not happen when the band overlap is corrected in the HSE06 functional. However, we find that LaAs undergoes a topological phase transition without breaking any symmetry under the effect of hydrostatic pressure at around 7 GPa. The crystal structure of LaAs remains unchanged under applied pressure up to 21 GPa, which is far above the topological phase transition pressure. These findings are important in exploring the novel topological states and their evolution from the viewpoint of topological phase transition in the family of rare-earth pnictides.