A team of LMU nanophysicists identifies new mechanisms of plasmonic damping

Metal nanostructures can concentrate light so strongly that they can trigger chemical reactions. The key players in this process are plasmons—collective oscillations of free electrons in the metal that confine energy to extremely small volumes. A new study published in Science Advances now shows how crucial adsorbed molecules are in determining how quickly these plasmons lose their energy.

The team led by LMU nanophysicists Dr. Andrei Stefancu and Prof. Emiliano Cortés identified two fundamentally different mechanisms of so-called chemical interface damping (CID), the plasmon damping caused by adsorbed molecules. Which mechanism dominates depends on how the electronic states of the molecule align with those of the metal surface, gold in this case — and this alignment is even reflected in the material’s electrical resistance.

Two mechanisms identifed

In the first mechanism, the molecule absorbs energy directly and resonantly: if the plasmon energy matches an unoccupied electronic state of the molecule, an electron can transition into this state immediately. This process is extremely fast and strongly dependent on the color (energy) of the incoming light.

The second mechanism works without such a resonant transition. Instead, electrons undergo diffuse, inelastic scattering at the interface between the gold surface and the molecule. This scattering causes the plasmons to lose energy—and increases the electrical direct-current resistance of the gold. The study shows that this scattering process and the plasmon damping are closely linked.

The findings bring together two phenomena that were previously studied separately: electrical surface effects and plasmonic energy transfer. They demonstrate that the flow of energy between light, metal, and molecules can be deliberately controlled simply by choosing which molecules are adsorbed on the surface. This opens new opportunities for light-driven catalysis, sensing technologies, and energy-efficient chemical processes.

The study was made possible through an international collaboration involving researchers from Imperial College London, the Universidad de La Laguna in Tenerife, and Rice University, working together with the LMU team. As highlighted by Emiliano Cortés: “These insights show that nanoscale energy flow can be tuned through molecular design, opening new possibilities for technology transfer and practical applicability. This is an important step toward sustainable processes that use sunlight to drive chemical reactions, including the production of fuels and high-value chemicals.“