Speaker: Alexey Kovalev (UNL)

Abstract:
We predict that a temperature gradient can induce a magnon-mediated spin Hall response in a collinear antiferromagnet with Dzyaloshinskii-Moriya interactions [1]. To address this problem, we develop a linear response theory based on the Luttinger approach of the gravitational scalar potential which gives a general condition for a Hall current to be well defined, even when the thermal Hall response is forbidden by symmetry. We apply our theory to honeycomb lattice antiferromagnet and study a role of magnon edge states in a finite geometry. As examples, we consider single and bi-layer honeycomb antiferromagnets where the nearest neighbor exchange interactions and the second nearest neighbor DMI are present. From our analysis, we suggest looking for the magnon-mediated spin Nernst effect in insulating antiferromagnets that are invariant under (i) a global time reversal symmetry or under (ii) a combined operation of time reversal and inversion symmetries. In both cases, the thermal Hall effect is zero while the spin Nernst effect could be present.

[1] V. A. Zyuzin and A. A. Kovalev, Phys. Rev. Lett. 117, 217203 (2016