Sunday, April 2, 2023

A new technique for ultrafast control of spins in a microscope

The breakthrough can advance “spintronics".

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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 needs to be improved by the chaotic nature of such fluctuations and the intrinsically irreversible switching between different minima in the magnetic energy landscape. Plus, the visualization and deterministic control of very few spins have yet to be achieved at ultrafast timescales.

Tengdin, Ph.D., student Benoit Truc and fellow postdoc Dr. Alexey Sapozhnik have developed a new technique to visualize and control the rotation of a handful of spins arranged in a vortex-like texture at the fastest speed ever achieved.

The scientists accomplished this using a series of femtosecond laser pulses (10-15 or a quadrillionth of a second). They could control the spins’ rotation in a selenium-copper mineral known in the field by its chemical formula, Cu2OSeO3, by precisely spacing out the laser pulses. Due to its great testbed for investigating spins, the mineral is relatively well-known in spintronics.

When scientists controlled the spins with laser pulses, they found they could switch their orientation at will by changing the delay time between successive driving pulses and adjusting the laser polarization.

The team was also able to image the spin changes thanks to a transmission electron microscope that can “see” tiny dimensions. The discovery has significant ramifications for spintronics’ core concepts.

Dr. Phoebe Tengdin, a postdoc in Carbone’s lab, said“Our experiments demonstrate that it is possible to manipulate and image a handful of spins at very high speed using a moderate intensity light beam. Such an effect can be exploited in low-consumption ultrafast devices operating on spins. New types of memories or logic gates are possible candidates, as are high-precision sensors.”

Journal Reference:

  1. Phoebe Tengdin, Benoit Truc, Alexey Sapozhnik, et al. Imaging the ultrafast coherent control of a skyrmion crystal. Physical Review X, 20 December 2022. DOI: 10.1103/PhysRevX.12.041030
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