Scientists just changed the nature of matter with a flash of light

It might sound like science fiction, yet this breakthrough is real. A team of physicists at the University of Konstanz, led by Davide Bossini, has developed an experimental technique that makes it possible. By using laser pulses to coherently excite pairs of magnons (quanta of spin waves), the researchers achieved remarkable effects that could influence both information technology and quantum research. Their findings were published in Science Advances.

Technology based on magnons

Before diving deeper, it helps to understand what magnons are and why they matter. The modern world generates enormous amounts of data through artificial intelligence and the "Internet of Things." Our current information systems are already straining under the pressure, and a data bottleneck threatens to slow technological progress.

One proposed solution is to use electron spins -- or even better, waves of many spins moving together -- to carry information. These collective spin oscillations are called magnons. They behave like waves and can be manipulated by lasers, potentially allowing data transmission and storage at terahertz frequencies.

So far, however, scientists have only been able to excite magnons at their lowest frequencies using light, which limits their potential. To harness magnons for future technologies, researchers must be able to tune their frequency, amplitude, and lifetime. The team at Konstanz has now found a way to do exactly that. By directly exciting pairs of magnons -- the highest-frequency magnetic resonances in a material -- they discovered a powerful new form of control.

A huge surprise

"The result was a huge surprise for us. No theory has ever predicted it," says Davide Bossini. Not only does the process work -- it also has spectacular effects. By driving high-frequency magnon pairs via laser pulses, the physicists succeeded in changing the frequencies and amplitudes of other magnons -- and thus the magnetic properties of the material -- in a non-thermal way. "Every solid has its own set of frequencies: electronic transitions, lattice vibrations, magnetic excitations. Every material resonates in its own way," explains Bossini. It is precisely this set of frequencies that can be influenced through the new process. "It changes the nature of the material, the 'magnetic DNA of the material', so to speak, its 'fingerprint'. It has practically become a different material with new properties for the time being," says Bossini.

"The effects are not caused by laser excitation. The cause is light, not temperature," confirms Bossini: "We can change the frequencies and properties of the material in a non-thermal way." The advantages are obvious: The method could be used for future data storage and for fast data transmission at terahertz rates without the systems being slowed down by the pileup of heat.

No spectacular high-tech materials or rare earths are required as the basis for the process, but rather naturally grown crystals -- namely the iron ore haematite. "Haematite is widespread. Centuries ago, it was already used for compasses in seafaring," explains Bossini. It is perfectly possible that haematite will now also be used for quantum research in the future. The results of the Konstanz team suggest that, using the new method, researchers will be able to produce light-induced Bose-Einstein condensates of high-energy magnons at room temperature. This would pave the way to researching quantum effects without the need for extensive cooling. Sounds like magic, but it is just technology and cutting-edge research.

The project was carried out in the context of the Collaborative Research Centre SFB 1432 "Fluctuations and Nonlinearities in Classical and Quantum Matter beyond Equilibrium."