Researchers at the University of Rostock, working at the Center for Interdisciplinary Electron Microscopy MV (ELMI-MV) in the Department of Life, Light, and Matter, in collaboration with the Collaborative Research Center “LiMatI,” have uncovered a surprising effect in tiny silver spheres.
Electrons oscillating in unison (plasmons) within tiny nanoparticles are influenced by their carbon substrate — essentially the balance beam on which they reside. The researchers visualized these plasmon resonances using high-resolution spectroscopy combined with simulation calculations and decomposed them into their individual modes — the various dances of the swaying electrons.
Contrary to the intuitive expectation that the influence of the substrate decreases with increasing distance, they observed a stronger energy decay precisely where the electron oscillation is excited furthest from the balance beam — a non-local effect. The studies demonstrate that this anomaly results from the geometry of the plasmon modes and the symmetry breaking caused by the substrate.
The results highlight that, for the technical application of such nano-resonators — for example, as light guides on a chip — the interaction with the substrate and the resulting mode splitting must be taken into account.
Publication:
Oldenburg, K., Meiwes-Broer, K.-H., und Barke, I.: Nonlocal substrate effect on supported silver clusters revealed by lifted plasmon degeneracy, Phys. Rev. Research, 7, 023267 (2025).
DOI: https://doi.org/10.1103/PhysRevResearch.7.023267