Thermal Hall effect in yttrium iron garnet (YIG) potentially due to magnon-polarons*

The theory of the magnon-polaron coupling interaction [1] in the ferrimagnet YIG has followed the experimental evidence substantiated by the spin Seebeck effect measurements conducted by Kikkawa. [2] It is also predicted that, at least in Kitaev antiferromagnets, a magnon-polaron driven thermal Hall effect can arise [3] due to the quantum-geometric Berry curvature of the magnon-polarons.  Motivated by this, we conducted thermal Hall measurement in a single-crystal YIG from 60K to 4K. We report new experimental data regarding the thermal Hall effect in YIG and show that the data demonstrate a field dependence in remarkable agreement with that of the magnon-polaron forming magnon and phonon dispersions.