Understanding Coupling in Hierarchically Doped Plasmonic Nanocrystal Metamaterials.

Mixtures of nanocrystals organized into dense monolayers can feature optical properties unattainable in films of homogeneous materials or in one-component nanocrystal assemblies. Doped metal oxide nanocrystals, which display metallic behavior with localized surface plasmon resonances that are tunable by dopant concentration, offer versatility as colloidal building blocks for such metasurfaces. By selecting nanocrystal components and mixing proportions, monolayers can be formed with multiple in- and out-of-plane collective plasmon resonances and broad spectral windows of near-zero permittivity. Here, we present a computational study using a mutual polarization method to assess how compositional correlations within a mixed binary monolayer of tin-doped indium oxide nanocrystals shift the balance between homo- and heterocoupling at a fixed nanocrystal mixing ratio, impacting optical properties from effective permittivity to near-field intensity spectra. The results highlight how the ability to control compositional ordering upon nanocrystal assembly would expand the design space available for creating metasurfaces with targeted optical responses.