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Ferroelectrics are seen as promising candidates for the electronics of tomorrow. An experiment at the world's largest X-ray laser—the European XFEL in Schenefeld near Hamburg—now shows that their properties can be controlled with high precision at ultrafast time scales—using light.

An international team of researchers led by Le Phuong Hoang and Giuseppe Mercurio from European XFEL has discovered a new way to manipulate the properties of ferroelectric materials extremely quickly and precisely with light. This breakthrough could pave the way for faster, more energy-efficient memory devices or electronic components. The findings are in the journal Nature Communications.

Ferroelectric materials are crystals in which positive and negative charges are slightly displaced from one another, generating an internal electric field—known as spontaneous polarization. This polarization can be reversed by applying an external electric field, making these materials ideal for use as nanoscale switches.

In this study, the researchers have now shown that the polarization can be altered independently of the lattice distortion to which it is usually closely linked. Until now, this decoupling had only been theorized—it had never been observed experimentally. The process was enabled by ultra-short, high-energy laser pulses, which excited the electrons in the material. This allowed the team to change the polarization extremely fast—in less than a trillionth of a second.

At the SCS instrument, the researchers studied barium titanate (BaTiO₃), a prototypical ferroelectric oxide, using the exceptionally bright and intense X-ray flashes of European XFEL, together with optical lasers. With their measurement techniques, they were able to track changes in the material's polarization, lattice structure and electronic state under the same conditions—with a temporal resolution of just 90 femtoseconds, or one-millionth of a billionth of a second.

They observed that just 350 femtoseconds after excitation by the laser, the polarization had already changed significantly—without the crystal lattice having had time to shift notably. "Our measurements show that the polarization was primarily controlled by photoexcited electrons rather than structural distortions," explains Le Phuong Hoang.

"This decoupling opens up new possibilities for designing future electronic components," adds Giuseppe Mercurio.

"Until now, achieving specific polarization states has required applying electric fields and complex circuitry. In future, light pulses could be sufficient. It might also be possible to manipulate magnetic properties in a similar way—for example, in so-called multiferroics, which can be controlled both electrically and magnetically," Mercurio predicts.

The study demonstrates a fundamentally new approach to controlling materials—not only faster, but also via mechanisms alternative to the typical approach of tailoring material properties by sample design. The researchers are convinced this marks an important step towards light-controlled electronics, with potentially wide-ranging applications in sensing technologies, data processing, and energy-efficient information storage.