Imaging the Ultrafast Coherent Control of a Skyrmion Crystal

Abstract

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 enable the imaging of random photogenerated 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 band gap of the Mott insulatorCu2OSeO3, 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.

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Plain Language Summary

Technological advancements in computation, data storage, and sensing all require new techniques to control the nanoscale magnetic properties of materials. Particularly important is the magnetic orientation of individual atoms, known as spin. Here, we provide a new protocol for controlling nanoscale magnetic textures on ultrafast timescales, offering exciting new opportunities for ultrafast spin switches in high-density next-generation information storage devices.

The visualization and control of very few spins has not yet been achieved on ultrafast timescales. Recently, researchers developed a new technique that can visualize and control the rotation of a handful of spins arranged in a vortexlike texture, called a skyrmion. We demonstrate a method to coherently control the rotation of a skyrmion crystal by discrete amounts at speeds that are orders of magnitude faster than those previously observed. By employing circularly polarized femtosecond laser pulses, we excite a collective magnon mode in the Mott insulatorCu2OSeO3. This triggers coherent magnetic oscillations that directly control the rotation of a skyrmion crystal, which we image with a type of electron microscopy. Additionally, we harness the insulating properties of this special skyrmion host material. This avoids heating effects and enables low-energy consumption devices.

The manipulation of topological order via ultrafast laser pulses shown here can be used to engineer fast spin-based logical devices.