Topological phase transition in LaAs under pressure

Abstract

Using density functional theory (DFT) calculations with the screened hybrid functional of Heyd, Scuseria, and Ernzerhof (HSE06), we study the effects of hydrostatic pressure on the electronic properties of LaAs. We focus on the band crossing near the $X$ point that can make LaAs a topological semimetal, discussing results of both DFT within the generalized gradient approximation (GGA) and the HSE06 hybrid functional. We find that in DFT-GGA, under the calculated equilibrium lattice parameter, LaAs displays a crossing between the highest As $p$ band and the lowest La $d$ band near the $X$ point due to the overestimated $p\text{\ensuremath{-}}d$ band overlap. Such crossing does not occur when the band overlap is corrected in the HSE06 calculation. However, we find that the $p\text{\ensuremath{-}}d$ crossing can be induced in LaAs under hydrostatic pressure, showing a topological phase transition at $\ensuremath{\sim}7\phantom{\rule{3.33333pt}{0ex}}\mathrm{GPa}$. The rocksalt crystal structure of LaAs is predicted to be stable under applied pressure up to 20 GPa, in good agreement with experimental observations.