When physicists at the University of Konstanz shone a flash of light on a simple iron crystal, they weren’t expecting to watch the rules of matter change before their eyes. Yet that seems to be what happened.
In an experiment that reads like science fiction, the team discovered a way to use light—not heat or exotic materials—to alter a substance’s magnetic properties, effectively turning one material into another in a fraction of a trillionth of a second.
The results, published in Science Advances, show that the effect doesn’t require supercooling or specialized alloys: it happens at room temperature. The light responsible doesn’t melt, burn, or deform the crystal. Instead, it simply changes the way its atoms behave. This process opens a door to new physics that merges the quantum and the macroscopic. With this, light itself can rewrite the physical identity of matter.
The researchers describe their discovery as a way to “change the frequencies and properties of the material in a non-thermal way.” In other words, they have shown that light alone, “not temperature,” can alter a material’s magnetic behavior, offering a new route to control magnetism without heat.
“Every solid has its own set of frequencies: electronic transitions, lattice vibrations, magnetic excitations,” lead author and physicist at the University of Konstanz, Dr. Davide Bossini, said in a statement. “Every material resonates in its own way. 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.”
Researchers used laser pulses to excite pairs of “magnons”—quantum waves that represent collective spin oscillations in a magnetic material. These magnons act like tiny disturbances or waves in a sea of electron spins. By controlling them, researchers found they could change the material’s magnetic “fingerprint.”
“The result was a huge surprise for us,” Dr. Bossini said. “No theory has ever predicted it.”
In essence, when light strikes the hematite crystal, it excites pairs of magnons to vibrate in sync. Those vibrations cascade through the lattice, coupling with other magnetic modes—types of oscillations in the arrangement of atomic spins—and reshaping the entire magnetic spectrum.
That transformation lasts only as long as the excited states persist—mere trillionths of a second—but it’s long enough to prove that light can temporarily redefine the intrinsic behavior of matter itself.
To achieve the effect, researchers used haematite, a naturally occurring iron ore once used in medieval compasses. “Haematite is widespread. Centuries ago, it was already used for compasses in seafaring,” Dr. Bossini said.
Using ultrafast laser pulses, each less than a millionth of a billionth of a second, the researchers could excite high-momentum magnons—quantized packets of spin waves that carry magnetic energy—within the hematite, a type of iron oxide. When these tiny magnetic waves coupled with lower-energy modes (slower, less energetic oscillations), the material’s resonance pattern shifted. This wasn’t a thermal effect from heating; it was purely quantum mechanical.
In their paper, the researchers verified this by changing the laser’s pulse rate and intensity. Even when the overall heat input varied by a factor of four, the results were identical. The magnetic states had changed, but not because of temperature. “The effects are not caused by laser excitation. The cause is light, not temperature,” Dr. Bossini confirmed.
In traditional physics, to alter a material’s state—for example, turning metal into a magnet—you’d need to heat, cool, or chemically modify it. However, here, the transformation is instantaneous and reversible.
Once the light stops, the material returns to its normal state. But for those fleeting moments, its magnetic behavior, and potentially its quantum properties, become something entirely new.
The experiment demonstrates a fundamental ability to control quantum phenomena at room temperature, something that has long eluded researchers. Normally, the delicate interactions behind quantum behavior collapse at everyday temperatures. However, by exciting magnon pairs, researchers achieved effects previously observable only near absolute zero.
These findings could have big implications for quantum technology. In quantum tech, information is stored and processed using magnetic spins and waveforms, not electric charges. This technique offers a way to modulate those spins without heat or energy loss. Heat and energy loss are major hurdles for developing fast and efficient quantum devices.
This ability to control magnetism with light could one day enable faster data storage and transmission at terahertz rates—without the thermal slowdowns that limit current electronic systems.
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