A first-principles investigation of topological phase transition in half-Heusler LiMgSb driven by volume expansive pressure

Abstract

Half-Heusler (HH) compounds are novel materials known for their diverse applications such as, magnetic semi-conductors, thermo-electrics and spintronic devices. Generally, HH systems are semi-conducting but, spin-locked surface states can be realized by application of stress/strain driving the system into Topological Phase Transition (TPT). In the current study, we use first-principles method to predict that, HH compound LiMgSb undergoes a TPT under the application of Volume Expansive Pressure (VEP). We find that, at 0% VEP the system exhibits a semi-conducting nature with indirect band gap. Whereas, at a considerably higher VEP (∼ 17 %) a Dirac Cone forms along the high symmetry point Γ in the Brillouin Zone (BZ). The existence of corresponding surface states have been confirmed by calculating, computational Angle Resolved Photo Emission Spectroscopy (ARPES). On further increment, the band reopens indicating Topological Insulator (TI) nature. We quantify the TI nature by calculating Z2 indices to conclude that, LiMgSb is a TI characterized by the Z2 indices as (0, 0 0 0). The predicted HH can thus have multi-functional applications in the field of spintronics and quantum computation.