Hall mass and transverse Noether spin currents in noncollinear antiferromagnets*

Noncollinear antiferromagnets (AFM) in the family of Mn3X (X=Ir, Sn, Ge, Pt, etc.) have attracted considerable interest as a platform for spintronics because they both possess the general benefits of antiferromagnets and exhibit various interesting transport, magnetic, and optical properties.  Here we study the conserved Noether current associated with spin-rotation symmetry of the local spins in noncollinear kagome AFM. We found that a transverse component of the d.c. Noether spin current can be created by a longitudinal driving force associated with a propagating spin wave and is proportional to a response coefficient that we denote as the Hall (inverse) mass, reminiscent of the isotropic spin Hall conductivity. We show the effect of the Hall mass and its association with transverse spin currents by simulating spin pumping in a ferromagnet (FM)-noncollinear AFM bilayer structure. Our results shed light on the potential of noncollinear AFM in manipulating the polarization and flow of spin currents in general spintronic devices.