Spin-Mediated Response in 2D Honeycomb Magnets*

Two-dimensional honeycomb ferromagnets that include a second nearest neighbor Dzyaloshinskii-Moriya interaction reproduce the Haldane model and are therefore expected to exhibit a non-trivial magnon band topology. It has been shown that such a system gives rise to a thermal Hall effect via magnon carriers. Likewise, chiral honeycomb antiferromagnets may generate a spin Nernst effect in response to the application of a temperature gradient. Recent theoretical studies modeling these spin-mediated responses in honeycomb magnets have been restricted to the linear spin wave limit – and are therefore only valid at low temperatures – or otherwise neglect to incorporate higher-order spin fluctuations which are crucial in the vicinity of the critical temperature.  In this talk, we will describe our approach to model the thermal Hall effect and spin Nernst effect in honeycomb magnets, particularly near and beyond the critical temperature. We will also show that spin-mediated response bolstered by increasing thermal fluctuations can be particularly robust at high temperatures, a result that is unexpected in the traditional magnon picture.