Researchers demonstrate ultrafast coherent control of a skyrmion crystal

Researchers at Switzerland EPFL, China's Anhui University, Germany's University of Cologne and University of New Hampshire in the US have developed a technique that can visualize and control the rotation of a handful of spins arranged in a vortex-like texture at the fastest speed ever achieved. The breakthrough can advance spintronics devices like computer memory, logic gates, and high-precision sensors.

"The visualization and deterministic control of very few spins has not yet been achieved at the ultrafast timescales," says Dr. Phoebe Tengdin, a postdoc at EPFL, pointing out the very tight timeframes that this control needs to happen for spintronics to ever make the leap into applications. Now, the team developed a new technique that can visualize and control the rotation of a handful of spins arranged in a vortex-like texture, a kind of spin "nano-whirlpool" called a skyrmion.

To do this, the scientists used sequences of laser pulses at a femtosecond timeframe (10-15 or a quadrillionth of a second). By arranging the laser pulses apart just right, they were able to control the rotation of spins in a selenium-copper mineral known in the field by its chemical composition, Cu2OSeO3. The mineral is quite popular in the field of spintronics, as it provides an ideal testbed for studying spins.

Controlling the spins with laser pulses, the researchers found that they could even switch their orientation at will by simply changing the delay time between successive driving pulses and adjusting the laser polarization.

Furthermore, by using using a type of transmission electron microscope that can detect nanoscale dimensions, the team was also able to actually image the spin changes.

The breakthrough could have significant implications for the fundamental aspects of spintronics. It offers the field a new protocol for controlling magnetic textures at ultrafast timescales, and opens up exciting new opportunities for spin switches in next-generation information storage devices.

"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," says Tengdin. "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."

Posted: Jan 28,2023 by Roni Peleg