Nonreciprocal transport of thermally generated magnons

We demonstrate the nonreciprocity of electrically and thermally generated incoherent magnon transport using the magnetization direction of a Py wire placed on top of an ultrathin YIG film. We show that the transport properties of thermally generated magnons under a Py wire depend on the relative orientation between the temperature gradient and the Py-magnetization direction. The symmetries of this nonreciprocal magnon transport match with those predicted by the remote dipolar interaction between YIG and Py magnons, controlled by the chirality of the YIG magnon dipolar stray fields. We also show that the directional magnon generation by the spin Seebeck effect from the Py wire displays the symmetries expected from the chiral spin Seebeck effect.