Deterministic control of skyrmion motion by Floquet engineering in altermagnets

Altermagnetic skyrmions hold great promise for spintronics by combining the ultrafast dynamics of antiferromagnets with the high accessibility of ferromagnets. However, achieving their deterministic manipulation remains a significant challenge due to the re-emergent skyrmion Hall effect. Here, we demonstrate deterministic control the dynamics of these textures via Floquet engineering. We firstly develop a theory to describe the Floquet dynamics of magnetic structures, combining a classical Heisenberg Hamiltonian, the Floquet-Magnus expansion, and the collective coordinate method. Applying this theory to a two-dimensional extrinsic altermagnet, we reveal frequency-reversible, directional skyrmion motion driven by light-induced asymmetric torque distributions. The direction reversal is achieved by exciting distinct skyrmion deformation modes through periodically modulated anisotropic exchange coupling. Furthermore, we show bound magnons within the skyrmion induce a non-dissipative drag and a velocity saturation at low damping. Interestingly, we uncover an enhanced skyrmion mobility at finite temperatures, facilitated by increased skyrmion deformation. This work establishes a theoretical framework for investigating light-induced non-equilibrium spin dynamics, and offers new avenues for controlling skyrmion motion.