Predicting the strain-mediated topological phase transition in 3D cubic ThTaN₃

The cubic ThTaN₃ compound has long been known as a semiconductor with a band gap of approximately 1 eV, but its electronic properties remain largely unexplored. By using density functional theory, we find that the band gap of ThTaN₃ is very sensitive to the hydrostatic pressure/strain. A Dirac cone can emerge around the Γ point with an ultrahigh Fermi velocity at a compressive strain of 8%. Interestingly, the effect of spin-orbital coupling (SOC) is significant, leading to a band gap reduction of 0.26 eV in the ThTaN₃ compound. Moreover, the strong SOC can turn ThTaN₃ into a topological insulator with a large inverted gap up to 0.25 eV, which can be primarily attributed to the inversion between the d-orbital of the heavy element Ta and the p-orbital of N. Our results highlight a new 3D topological insulator with strain-mediated topological transition for potential applications in future spintronics.