Seminar: Spin Nernst effect and pumping of spin current in a collinear antiferromagnet

Dr. Alexey A. Kovalev from University of Nebraska in Lincoln (USA) will visit Spintec and give the seminar on July 10 at 14:00 entitled

“Magnon-mediated spin Nernst effect and pumping of spin current in a collinear antiferromagnet”

Date: Monday July 10 at 14:00
Place: CEA/Spintec, Bat. 1005, room 434

Abstract: We predict that a temperature gradient can induce a magnon-mediated spin Hall response in a collinear antiferromagnet with Dzyaloshinskii-Moriya interactions [1]. An experiment consistent with such prediction has recently been reported [2]. 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 [3,4]. In case of a collinear antiferromagnet, such torques become staggered and can control the dynamics of the Neel order parameter. In systems with broken inversion symmetry, such torques can also have a component associated with accumulation of the Berry phase. The Onsager reciprocal effect suggests that it should be possible to pump magnon-mediated spin current by a Neel order dynamics.

[1] V. Zyuzin, A.A. Kovalev, Phys. Rev. Lett. 117, 217203 (2016).
[2] Y. Shiomi, R. Takashima, E. Saitoh, arXiv:1706.03978
[3] A.A. Kovalev, V. Zyuzin, Phys. Rev. B 93, 161106 (2016).
[4] A.A. Kovalev, V. Zyuzin,, Bo Li, Phys. Rev. B 95, 165106(2017)

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