Pressure-induced topological phase transition in XMR material YbAs: a first-principles study

Many rare-earth monopnictides having extremely large magnetoresistance (XMR) show topologically non-trivial nature under applied hydrostatic pressure. We find that YbAs which show XMR effect, is stable in rocksalt structure (NaCl-type) for entire studied pressure range (0–40 GPa). The structural phase transition to CsCl-type structure takes place at 67 GPa which is in fine agreement with previous experimental study. We also verify its dynamical stability from phonon dispersion spectrum. This material undergoes topological phase transition (trivial to non-trivial) under applied hydrostatic pressure of 6 GPa and retains this non-trivial nature up to 39.5 GPa without breaking any symmetry. This quantum phase transition is associated with spin–orbit coupling effect. We find the band inversions near the Fermi level at X and Γ point at 6 GPa and 39.5 GPa, respectively, and verified the same with the help of band parities.