Magnetoelastic coupling enabled tunability of magnon spin current generation in two-dimensional antiferromagnets

© 2021 American Physical Society.We theoretically investigate the magnetoelastic coupling (MEC) and its effect on magnon transport in two-dimensional antiferromagnets with a honeycomb lattice. MEC coefficients along with magnetic exchange parameters and spring constants are computed for monolayers of transition-metal trichalcogenides with Néel magnetic order (MnPS3 and VPS3) and zigzag order (CrSiTe3, NiPS3, and NiPSe3) by ab initio calculations. Using these parameters, we predict that the spin-Nernst coefficient is significantly enhanced due to magnetoelastic coupling. Our study shows that although Dzyaloshinskii-Moriya interaction can produce spin-Nernst effect in these materials, other mechanisms such as magnon-phonon coupling should be taken into account. We also demonstrate that the magnetic anisotropy is an important factor for control of magnon-phonon hybridization and enhancement of the Berry curvature and thus the spin-Nernst coefficient. Our results pave the way toward gate tunable spin current generation in two-dimensional magnets by spin-Nernst effect via electric field modulation of MEC and anisotropy.11Nsciescopu

Symmetry enhanced spin-Nernst effect in honeycomb antiferromagnetic transition metal trichalcogenide monolayers

We investigate systematically the spin-Nernst effect in Neel and zigzag ordered honeycomb antiferromagnets. Monolayers of transition-metal trichalcogenides, MnPSe3, MnPS3, and VPS3 show an antiferromagnetic Neel order while CrSiTe3, NiPS3, and NiPSe3 show an antiferromagnetic zigzag order. We extract the exchange and Dzyaloshinskii-Moriya interaction parameters from ab initio calculations. Using these parameters, we predict that the spin-Nernst coefficient is at least two orders of magnitude larger in zigzag compared to the Neel ordered antiferromagnets. We find that this enhancement relies on the large band splitting due to the symmetry of magnetic configuration in the zigzag order. Our calculations indicate that the Dzyaloshinskii-Moriya interaction is the underlying factor for the spin-Nernst effect in both cases, although with different microscopic mechanisms. In the case of Neel antiferromagnets, magnon bands already possess a Berry curvature and introducing the Dzyaloshinskii-Moriya interaction splits the magnon bands with the opposite helicity throughout the Brillouin zone which results in an unbalanced population of magnons carrying opposite spins. In the case of zigzag antiferromagnets, magnon bands do not possess the Berry curvature but they are split for opposite helicity magnons due to symmetry of the system. In this case, introducing the Dzyaloshinskii-Moriya interaction induces the Berry curvature and results in the spin-Nernst effect. Due to large magnon band splitting, the spin-Nernst effect in zigzag antiferromagnets is stronger than Neel antiferromagnets