Scientists have discovered a way to make molecules sitting on a flat surface rotate together using extremely short flashes of light.
The discovery could eventually help researchers design faster electronics, advanced data storage systems, and new energy technologies.
The research was carried out by an international team from Germany, Japan, and India, led by scientists from DESY and the Universities of Kiel and Hamburg.
By using ultrafast light pulses from DESY’s free-electron laser FLASH and another advanced laser source, the team was able to trigger coordinated motion in molecules placed on special quantum materials.
The study was recently published in Nature Communications.
Normally, molecules that sit on the surface of a material remain mostly still. However, when energy is delivered to them—for example through light—they can start to move.
Scientists have long wondered whether this movement could be controlled in a precise way.
If so, it could open new possibilities for nanotechnology, including molecular electronics and advanced materials that respond to light or energy.
In this study, the researchers focused on hybrid systems where organic molecules are placed on extremely thin quantum materials that are only one or a few atoms thick. These combinations are of great interest to scientists because they can have unique electrical and chemical properties.
When the researchers illuminated the system with ultrafast light pulses, something remarkable happened.
The light caused some of the electric charge in the quantum material to transfer to the molecules sitting on top. This temporary change in charge altered the forces acting on the molecules and caused many of them to rotate at nearly the same time.
To observe these rapid changes, the team used a sophisticated technique called time-resolved momentum microscopy at the FLASH free-electron laser. This allowed them to track how electrons moved, how energy levels shifted, and how the molecules themselves rotated.
Because these events occur extremely quickly—within just a few hundred femtoseconds, or trillionths of a second—the scientists used an approach they described as creating a “multiplexed electronic movie.”
They fired ultrashort pulses of extreme ultraviolet and soft X-ray light at the material. The light knocked electrons out of the sample, and a special camera recorded their energy and direction. By combining several types of measurements in one experiment, the researchers could reconstruct what was happening step by step at the atomic scale.
The experiments revealed that when the light pulse hits the surface, a rapid transfer of charge occurs between the quantum material and the molecules. This brief change in electrical conditions causes a large group of molecules to rotate together in a synchronized way.
Interestingly, the collective rotation temporarily creates a chiral arrangement among the molecules.
Chirality refers to a kind of “handedness” in structure, similar to how left and right hands are mirror images but not identical. What makes this discovery especially surprising is that the individual molecules themselves are not naturally chiral.
The findings could be important for several emerging technologies. Scientists are particularly interested in molecular switches—molecules that can change between different stable states when triggered by light or other signals. Such switches could one day form the basis of electronic components built from single molecules, potentially leading to extremely small and energy-efficient computing devices.
Chiral materials are also crucial in many areas of chemistry and biology, including drug development, where the exact orientation of molecules can determine how a medicine works.
Although practical applications are still in the future, the researchers say this work provides an important step toward controlling molecular motion using light.
Future studies will explore how to better control, stabilize, or switch this light-driven movement so that it can eventually be used in real technologies.
Source: KSR.
