The principle “Work smarter, not harder!” apparently also applies to controlling quantum materials with light. Many of their fascinating properties depend on how the atoms are arranged in the crystal. Ultrashort laser pulses can be used to alter these structures in a targeted way—the light first excites electrons, whose changed energy and dynamics exert forces on the atomic nuclei and can thereby set the atoms in motion. Such processes unfold within femtoseconds, a millionth of a billionth of a second.

In a study now published in Nature Physics, researchers from the Universities of Würzburg and Rostock and from ETH Zurich investigated this mechanism in WTe₂, a so-called sliding ferroelectric. In such materials, neighboring atomic layers can slide 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.