Breaking the Mode Degeneracy of Surface-Plasmon Resonances in a Triangular System

TL;DR

This study systematically breaks the symmetry in triangular gold nanoprisms to lift mode degeneracy, revealing how symmetry alterations affect plasmonic resonances, damping, and eigenenergies in Fano-type resonances.

Contribution

It introduces a method to control plasmonic mode degeneracy by symmetry-breaking in triangular nanoprisms, a novel approach for tuning plasmonic properties.

Findings

Symmetry-breaking lifts mode degeneracy.

Altered damping and eigenenergies of resonances.

Controlled tuning of Fano resonances.

Abstract

In this paper, we present a systematic investigation of symmetry-breaking in the plasmonic modes of triangular gold nanoprisms. Their geometrical C3 symmetry is one of the simplest possible that allows degeneracy in the particle's mode spectrum. It is reduced to the non-degenerate symmetries Cv or E by positioning additional, smaller gold nanoprisms in close proximity, either in a lateral or a vertical configuration. Corresponding to the lower symmetry of the system, its eigenmodes also feature lower symmetries (Cv), or preserve only the identity (E) as symmetry. We discuss how breaking the symmetry of the plasmonic system not only breaks the degeneracy of some lower order modes, but also how it alters the damping and eigenenergies of the observed Fano-type resonances.