Dynamical switching of magentic topology in microwave-driven itinerant magnet

Magnetic skyrmion crystals (SkXs) are magnetic textures characterized by a topological invariant called skyrmion number Nsk, which are often stabilized by the Dzyaloshinskii-Moriya interactions (DMI) in chiral magnets. Recently, SkXs have been discovered successively in centrosymmetric itinerant magnets without active DMI as well, and they are considered to be stabilized by a different mechanism, i.e., conduction-electron-mediated spin-spin interactions. Because the DMI is absent, the SkXs in such magnets have several unfrozen degrees of freedom associated with the swirling spin configurations, e.g., vorticity and helicity, which provide us with a unique opportunity to switch the magnetic topology by external stimuli. In this work, we theoretically demonstrate that the magnetic topology of SkX in Kondo-lattice magnets can be switched among Nsk=2, 1, and 0 by irradiating with circularly polarized microwave field via intensely exciting a resonance mode [1]. This topology switching exhibits various behaviors possibly due to different dynamical landscape of energies, that is, deterministic irreversible switching, probabilistic irreversible switching, and temporally random fluctuation.

[1] R. Eto and M. Mochizuki, Phys. Rev. B 104, 104425 (2021).