Intrinsic spin Nernst effect of magnons in a noncollinear antiferromagnet

We investigate the intrinsic magnon spin current in a noncollinear antiferromagnetic insulator. To this end, we derive a magnon spin current in a noncollinear antiferromagnet from continuity equation and find that in general it is not conserved, but for certain symmetries and spin polarizations, the averaged effect of non-conserving terms can vanish. We formulate a general linear response theory for magnons in noncollinear antiferromagnets subject to a temperature gradient and analyze the effect of symmetries on the response tensor. We apply this theory to single-layer potassium iron jarosite KFe3(OH)6(SO4)2 and predict a measurable spin current response. According to the symmetry analysis, many other material candidates should exhibit the spin Nernst effect, including quasi-two- and three-dimensional noncollinear antiferromagnets and antiferromagnets with magnetic textures such as skyrmions. Our proposal can be useful for spin generation in spintronics applications. Furthermore, this effect can also serve as a probe for the materials that can hold multiple noncollinear states.