Two synchronized light pulses induce an amplified sliding vibration in the atomic layers of WTe₂. Credit: Gerrit Horstmann

Researchers have uncovered an unexpected way to control the movement of atomic layers in quantum materials.

Scientists have discovered that two carefully timed laser pulses can move atomic layers in a quantum material more effectively than a single, more powerful pulse. Published in Nature Physics, the research shows that increasing light intensity can actually limit atomic motion, while controlling when the energy arrives can overcome that restriction.

The discovery comes from researchers at the Universities of Würzburg and Rostock and ETH Zurich, who investigated tungsten ditelluride (WTe₂), a material known as a sliding ferroelectric. Its neighboring atomic layers can shift sideways against each other, much like two palms pressed together.

“What makes this particularly exciting is that the relative motion of the atomic layers can influence a range of material properties, such as ferroelectricity and topology,” explains Gerrit Horstmann, first author of the study and head of an Emmy Noether junior research group at the University of Würzburg.

Why Stronger Laser Pulses Can Slow Atomic Motion

Ultrashort laser pulses can change a crystal’s structure by transferring energy to its electrons. As the electrons respond, they exert forces on atomic nuclei, setting the atoms in motion. These processes occur within femtoseconds, with each femtosecond lasting just one millionth of a billionth of a second.

Increasing the laser’s intensity might seem like an obvious way to produce greater movement, but the researchers found that this approach has a fundamental limitation. “Under very strong excitation, electrons are promoted into high-energy states that counteract the directed motion of the atoms. The additional light energy then no longer produces a correspondingly larger displacement of the atomic layers; instead, it effectively slows them down,” explains Gerrit Horstmann.

Using Two Laser Pulses to Control Quantum Materials

To bypass this limitation, the team divided the laser energy between two weaker pulses delivered at different times. After the first pulse, the excited electrons have time to partially relax before the second pulse arrives. By adjusting the delay, the researchers can reinforce the sliding motion of the atomic layers, similar to pushing a child on a swing at precisely the right moment.

“Timing opens up an additional way to make optimal use of the interaction between electrons and atomic motion,” says Horstmann. Rather than forcing the atoms to move with increasingly powerful pulses, the technique uses the material’s own electronic and atomic dynamics to achieve more effective control. The approach follows a familiar principle: “Work smarter, not harder!”

A Possible Path to More Energy-Efficient Electronics

Controlling how atomic layers slide could eventually provide a way to switch technologically useful properties, including ferroelectric polarization, with less energy. The technique may be particularly valuable for ultrathin materials such as WTe₂, which can consist of only a few atomic layers and are being explored for compact electronic devices.

Although practical applications remain a longer-term goal, the findings establish a strategy for manipulating quantum materials through the timing of light pulses rather than simply increasing their intensity. As the researchers put it, “Work smarter, not harder!”

Reference: “Coherent phonon control beyond amplitude saturation in a sliding ferroelectric” by Jan Gerrit Horstmann, Christoph Emeis, Andrin Caviezel, Quintin N. Meier, Nicolas Wyler, Thomas Lottermoser, Fabio Caruso and Manfred Fiebig, 21 October 2026, Nature Physics.
DOI: 10.1038/s41567-026-03491-1

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