Dresden 2017 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 53: Focus Session: Topology meets Magnetism

MA 53.3: Hauptvortrag

Donnerstag, 23. März 2017, 16:15–16:45, HSZ 01

Magnon-mediated Dzyaloshinskii-Moriya torques, heat pumping, and spin Nernst effect — •Alexey Kovalev — University of Nebraska-Lincoln, USA

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. We also consider transport of magnons and its relation to non-equilibrium magnon-mediated spin torques [2]. We apply our theory to the magnon-mediated Nernst and torque responses in systems realizing Weyl magnons.

[1] Phys. Rev. Lett. 117, 217203 (2016)

[2] Phys. Rev. B 93, 161106 (2016)