Orbital contribution to the regulation of the spin-valley coupling in antiferromagnetic monolayer MnPTe3

In addition to the ferromagnetic materials with inversion symmetry breaking, the symmetric antiferromagnetic materials also exhibit intrinsic valley splitting due to the spin-valley coupling. Using first-principles calculations, we investigated the manipulation of valley splitting of antiferromagnetic monolayer ${\mathrm{MnPTe}}_{3}$ via biaxial strain. It is shown that two ${\mathrm{MnPTe}}_{3}$ monolayers with different structures are both stable antiferromagnetic semiconductors, and exhibit valley splitting between $K$ and ${K}^{\ensuremath{'}}$. The spin-valley coupling strength can be greatly tuned by in-plane strain, which is due to the changes of orbital composition of electronic state and the different contribution of two sublattice atoms. The proportions of $d$ orbitals of Mn atoms determine the orbital angular momentum of the electronic state, and the different contribution of different sublattices results in the change of Berry curvature at $K$ and ${K}^{\ensuremath{'}}$ points. The combination of two factors leads to the same changes of valley splitting and the proportion of the ${d}_{xz}$, ${d}_{yz}$ orbitals. These results of are some significance for the design of materials with greater valley splitting and the understanding of its mechanism.