Tunable large spin Nernst effect in a two-dimensional magnetic bilayer

TL;DR

This paper theoretically explores how topological spin transport, specifically the spin Nernst effect, can be tuned in two-dimensional magnetic bilayers, especially around phase transitions between ferromagnetic and antiferromagnetic states.

Contribution

It introduces a theoretical framework for tunable topological spin transport in 2D magnetic bilayers, highlighting the role of magnon-polarons and spin Berry curvature near phase transitions.

Findings

Spin Berry curvature is large in layered antiferromagnets due to small energy gaps.

Spin Nernst conductivity exhibits abrupt changes at magnetic phase transitions.

Interband transitions enable topological spin transport even with preserved time-reversal symmetry.

Abstract

We theoretically investigate topological spin transport of the magnon-polarons in bilayer magnet with two-dimensional square lattices. Our theory is motivated by recent reports on the van der Waals magnets which show the reversible electrical switching of the interlayer magnetic order between antiferromagnetic and ferromagnetic orders. The magnetoelastic interaction opens band gaps and allows the interband transition between different excitation states. In the layered antiferromagnet, due to the interband transition between the magnon-polaron states, the spin Berry curvature which allows the topological spin transport occurs even if the time-reversal symmetry is preserved. We find that the spin Berry curvature in the layered antiferromagnet is very large due to the small energy spacing between two magnon-like states. As a result, the spin Nernst conductivity shows sudden increase (or decrease) at the phase transition point between ferromagnetic and antiferromagnetic phases. Our result suggest that the ubiquity of tunable topological spin transports in two dimensional magnetic systems.