Bidirectional spin-wave-driven domain wall motion in ferrimagnets

We investigate ferrimagnetic domain-wall dynamics induced by circularly polarized spin waves theoretically and numerically. We find that the direction of domain-wall motion depends on both the circular polarization of spin waves and the sign of net spin density of the ferrimagnet. Below the angular momentum compensation point, left- circularly (right-circularly) polarized spin waves push a domain wall towards (away from) the spin-wave source. Above the angular momentum compensation point, on the other hand, the direction of domain-wall motion is reversed. This bidirectional motion originates from the fact that the sign of spin-wave-induced magnonic torque depends on the circular polarization and the subsequent response of the domain wall to the magnonic torque is governed by the net spin density. Our finding provides a way to utilize a spin wave as a versatile driving force for bidirectional domain-wall motion.