Nonlinear magnon spin Nernst effect in antiferromagnets and strain-tunable pure spin current*

The topological properties of magnons, as exemplified by the magnon spin Nernst effect (SNE) in antiferromagnets [1], offer great potential for spin current generation in magnetic materials. However, many of them are studied in the linear response regime and their realization is often limited to the magnets which have, such as, nonnegligible Dzyaloshinskii-Moriya (DM) interaction. On the other hand, nonlinear topological responses of magnons are expected to be realized in a wide range of materials, as can be imagined from the nonlinear Hall effect in electronic systems [2].

We study the SNE of magnons in the nonlinear response regime [3]. We derive the formula for the nonlinear magnon spin Nernst current by solving the Boltzmann equation. The nonlinear magnon SNE is expected to occur in various Neel antiferromagnets without DM interaction. Thus, it will be one of a few possible ways to generate spin current in materials with negligible DM interaction. In particular, the nonlinear spin Nernst current in the honeycomb and diamond lattice antiferromagnets can be controlled by strain/pressure.

[1] R. Cheng, S. Okamoto, and D. Xiao, Phys. Rev. Lett. 117, 217202 (2016).

[2] I. Sodemann and L. Fu, Phys. Rev. Lett. 115, 216806 (2015).

[3] H. Kondo and Y. Akagi, arXiv:2109.09464.