Giant strain-induced spin splitting effect in MnTe, a $g$-wave altermagnetic semiconductor

Hexagonal MnTe is an altermagnetic semiconductor with $g$-wave symmetry of spin polarization in momentum space. In the nonrelativistic limit, this symmetry mandates that electric current flowing in any crystallographic direction is unpolarized. However, it is shown that elastic strain is effective in inducing the spin splitting effect in MnTe. For this analysis, a spin-orbit-coupled $\mathbf{k}\cdot\mathbf{p}$ Hamiltonian for the valence band maximum at the A point is derived and fitted to eigenvalues calculated from first principles. The spin splitting angle is calculated using the Boltzmann approach in the relaxation-time approximation. The spin splitting gauge factor exceeds 20 near the valence band maximum. Thus, with suitable substrate engineering, MnTe can be used as an efficient source and detector of spin current in spintronic devices. Proper inclusion of the Rashba-Dresselhaus spin-orbit coupling is crucial for the correct description of the transport properties of MnTe.