Magnetic spin modulation by optical vortex-induced spin-spin interaction

We investigate how an optical vortex radiation modulates magnetic spin order of a metallic chiral magnet. The optical vortex carries its intrinsic orbital angular momentum and has a toroidal field intensity, hence such a helical beam is expected to couple to angular momentum of electrons. Here we theoretically construct microscopic interactions between an optical vortex and electrons in the chiral magnet. As a result, we derive a spin-spin interaction which is induced by the optical vortex radiation in the one-dimensional tight-binding model, and find that this interaction can modulate the magnetic order. The optical vortex should be one of the plausible candidates for spin control source, and open a new door to future spintronics devices.