Strong Coupling in Two-Phase Metamaterials Fabricated by Sequential Self-Assembly

Self-assembly processes provide the means to achieve scalable and versatile
metamaterials by “bottom-up” fabrication. Despite their enormous potential,
especially as a platform for energy materials, self-assembled metamaterials
are often limited to single phase systems, and complex multi-phase
metamaterials have scarcely been explored. A new approach based on
sequential self-assembly (SSA) that enables the formation of a two-phase
metamaterial (TPM) composed of a disordered network metamaterial with
embedded nanoparticles (NPs) is proposed. Taking advantage of both the
high-spatial and high-energy resolution of electron energy loss spectroscopy
(EELS), inhomogeneous localization of light in the network is observed,
concurrent with dipolar and higher-order localized surface plasmon modes in
the nanoparticles. Moreover, it is demonstrated that the coupling strength
deviates from the interaction of two classical dipoles when entering the strong
coupling regime. The observed energy exchange between two phases in this
complex metamaterial, realized solely through self-assembly, implies the
possibility to exploit these disordered systems for plasmon-enhanced
catalysis.