Nonlinear spin current of photoexcited magnons in collinear antiferromagnets

Generation of spin currents is currently actively studied from the viewpoint of magnon spintronics. Here, the authors propose that ac electric field can excite magnons and induce nonlinear spin currents in antiferromagnets with broken inversion symmetry. In particular, they show that linearly polarized light generates magnon spin shift current that originates from the nontrivial geometry of the magnon band and is closely related to the electronic shift current in semiconductors. The authors demonstrate that the photoinduced spin current is accessible for measurements in the multiferroic compound Mn${}₂$Mo${}₃$O${}₈$.