Multiple Embedded Eigenstates in Nonlocal Plasmonic Nanostructures

TL;DR

This paper explores how nonlocal effects in plasmonic nanostructures enable multiple embedded eigenstates, allowing light trapping at various frequencies without strict zero-permittivity conditions, thus advancing nanophotonics.

Contribution

It reveals that spatial dispersion effects in nonlocal plasmonic materials facilitate multiple trapped light states, relaxing previous constraints for light confinement.

Findings

Nonlocality creates new degrees of freedom for light trapping.

Multiple frequencies can achieve suppressed radiation loss.

Zero-permittivity condition is no longer necessary.

Abstract

Trapping light in open cavities is a long sought "holy grail" of nanophotonics. Plasmonic materials may offer a unique opportunity in this context, as they may fully suppress the radiation loss and enable the observation of spatially localized light states with infinite lifetime in an open system. Here, we investigate how the spatial dispersion effects, e.g., caused by the electron-electron interactions in a metal, affect the trapped eigenstates. Heuristically, one may expect that the repulsive-type electron-electron interactions should act against light localization, and thereby that they should have a negative impact on the formation of the embedded eigenstates. Surprisingly, here we find that the nonlocality of the material response creates new degrees of freedom and relaxes the requirements for the observation of trapped light. In particular, a zero-permittivity condition is no longer mandatory and the same resonator shell can potentially suppress the radiation loss at multiple frequencies.