  Exotic magnetic textures emerging from the subtle interplay between
thermodynamic and topological fluctuation have attracted intense interest due
to their potential applications in spintronic devices. Recent advances in
electron microscopy have enabled the imaging of random photo-generated
individual skyrmions. However, their deterministic and dynamical manipulation
is hampered by the chaotic nature of such fluctuations and the intrinsically
irreversible switching between different minima in the magnetic energy
landscape. Here, we demonstrate a method to coherently control the rotation of
a skyrmion crystal by discrete amounts at speeds which are much faster than
previously observed. By employing circularly polarized femtosecond laser pulses
with an energy below the bandgap of the Mott insulator Cu2OSeO3, we excite a
collective magnon mode via the inverse Faraday effect. This triggers coherent
magnetic oscillations that directly control the rotation of a skyrmion crystal
imaged by cryo-Lorentz Transmission Electron Microscopy. The manipulation of
topological order via ultrafast laser pulses shown here can be used to engineer
fast spin-based logical devices.
