Artist's impression: Two time-tuned light pulses cause the atomic layers in WTe2 to undergo an enhanced sliding vibration.
Image Credit: Gerrit Horstmann (JMU); computer rendered with support from Claude (Anthropic)
Scientific Frontline: Extended "At a Glance" Summary: Optical Control of Quantum Materials
The Core Concept: Researchers have discovered a method to control the atomic structure of quantum materials, specifically sliding ferroelectrics like tungsten ditelluride, using targeted sequences of time-delayed ultrashort laser pulses. By timing the pulses instead of simply increasing laser intensity, physicists can optimize the interaction between electrons and atomic motion to manipulate material properties efficiently.
Key Distinction/Mechanism: Unlike traditional approaches that increase laser energy to drive stronger atomic displacement—which can paradoxically excite electrons into states that inhibit movement—this method splits the energy into two weaker pulses. The time delay allows the electronic system to partially relax before the second pulse arrives, driving the atomic layers to slide efficiently in a manner analogous to pushing a child on a swing.
Origin/History: This mechanism was detailed in a 2026 study published in Nature Physics by researchers from the University of Würzburg, the University of Rostock, and ETH Zurich, marking a significant advancement in the optical control of quantum materials.
Major Frameworks/Components:
- Coherent Phonon Control: Using light to induce and manipulate organized atomic vibrations (phonons) within a crystal lattice.
- Sliding Ferroelectricity: A phenomenon in layered van der Waals materials where adjacent atomic layers slide against each other, altering properties like topology and electrical polarization.
- Amplitude Saturation Bypass: Overcoming the natural limits of single-pulse excitation by matching the light delivery to the intrinsic dynamics of the material.
Branches of Science: Condensed Matter Physics, Femtosecond Physics, Materials Science, Optoelectronics, and Quantum Mechanics.
Future Application: This technique paves the way for the energy-efficient switching of ferroelectric polarization in ultrathin, few-atom layers, which is critical for developing highly compact, next-generation electronic components and quantum computing architectures.
Why It Matters: It establishes a new paradigm in light-matter interaction, proving that meticulously timed excitation is far more effective than sheer energy input when altering a material's fundamental properties, fulfilling the principle of working smarter rather than harder in quantum engineering.
A new study shows that a targeted temporal sequence of light pulses can amplify the movement of atomic layers in a quantum material. In this way, functional material properties can be efficiently controlled.
Targeted excitation strategies are more effective than uniform energy increases when controlling quantum materials with light. Many of these macroscopic properties depend on atomic arrangement within the crystal lattice. Using ultrashort laser pulses, these structures can be altered in a targeted manner: the light initially excites electrons, whose altered energy and dynamics exert forces on the atomic nuclei, thereby triggering atomic movements. Such processes occur within femtoseconds—one millionth of one billionth of a second.
In a study recently published in Nature Physics, researchers from the University of Würzburg, the University of Rostock, and ETH Zurich investigated this mechanism in WTe2, a sliding ferroelectric. In such materials, weak interlayer bonding permits adjacent atomic layers to slide against each other. Gerrit Horstmann, first author of the study and leader of an Emmy Noether junior research group at Julius-Maximilians-Universität Würzburg (JMU), noted that the relative movement of atomic layers can dictate material properties such as ferroelectricity and topology.
More Light Does Not Always Lead to More Movement
It would seem logical to simply increase the energy of the laser pulse to achieve a stronger displacement of the atomic layers. However, the researchers show that this strategy has its limits. “With very strong excitation, electrons are excited into high-energy states that counteract the directed movement of the atoms. The additional light energy then no longer leads to a correspondingly stronger displacement of the atomic layers, but actually slows them down,” explains Horstmann.
Instead of further increasing the intensity, the researchers chose a different approach: they divided the light energy into two weaker, temporally separated pulses. After the first pulse, the electronic system is given time to partially relax before the second pulse arrives. By precisely selecting the time delay to match the material's structural resonance, the sliding movement is amplified, thereby overcoming the amplitude saturation limitations of single-pulse excitation. “The timing opens up an additional possibility to optimally utilize the interaction between electrons and atomic movement,” says Horstmann. Instead of introducing as much energy as possible all at once, the excitation is adapted to the dynamics of the material.
New Possibilities for the Control of Quantum Materials
In the long term, these results could help to switch technologically relevant properties, such as ferroelectric polarization, in an energy-efficient manner. This approach is particularly interesting for ultrathin materials like WTe2, which consist of only a few atomic layers and offer new perspectives for compact electronic components.
The study thus illustrates a fundamental principle of light control: higher energy is not necessarily decisive for achieving the desired properties of a material; rather, a better-coordinated temporal excitation can determine the outcome.
Funding: J.G.H. acknowledges funding by an ETH Postdoctoral Fellowship, a Swiss National Science Foundation (SNSF) Postdoctoral Fellowship (TMPFP2 217303), an ETH Seed Grant, the Daimler and Benz Foundation, and the Emmy Noether Program of the Deutsche Forschungsgemeinsschaft (DFG), project no. 577668401. Q.N.M. acknowledges funding by PEPR SPIN–MALT (ANR-24-EXSP-0006). Computational resources were provided by GENCI grant no. 2025-AD010916740. F.C. and C.E. acknowledge funding by the DFG, project no. 499426961, and from the European Union as part of the MSCA Doctoral Network TIMES (grant agreement no. 101118915). F.C. and C.E. also acknowledge computing time on the high-performance computer Lichtenberg II at TU Darmstadt, funded by the German Federal Ministry of Education and Research (BMBF) and the State of Hesse Ministry of Science and Research, Art and Culture (HMWK), project no. p0021280. The project was supported by the Swiss National Science Foundation through SNSF grant no. 200021_219807. Open access funding provided by Julius-Maximilians-Universität Würzburg.
Published in journal: Nature Physics
Title: Coherent phonon control beyond amplitude saturation in a sliding ferroelectric
Authors: Jan Gerrit Horstmann, Christoph Emeis, Andrin Caviezel, Quintin N. Meier, Nicolas Wyler, Thomas Lottermoser, Fabio Caruso, and Manfred Fiebig
Source/Credit: University of Würzburg
Edited by: Scientific Frontline
Reference Number: phy110426_01
