Spin transport in noncollinear antiferromagnetic metals

For noncollinear antiferromagnetic metals, magnon spectra display nontrivial multiband structure in which both direction and magnitude of the angular momenta of magnons are momentum dependent. We study the roles of these magnons on the spin transport properties by taking into account the momentum and angular momentum transfer between conduction electrons and magnons. We have calculated spin conductivity tensor by using the coupled Boltzmann equations for the electron spin and magnon, and we show that the unpolarized electron current driven by an electric field can efficiently induce a magnon spin current. The temperature dependence of the magnon spin conductivity is also calculated.