title: Robustness of the far-field response of nonlocal plasmonic ensembles.
abstract: Contrary to classical predictions, the optical response of few-nm plasmonic particles depends on particle size due to effects such as nonlocality and electron spill-out. Ensembles of such nanoparticles are therefore expected to exhibit a nonclassical inhomogeneous spectral broadening due to size distribution. For a normal distribution of free-electron nanoparticles, and within the simple nonlocal hydrodynamic Drude model, both the nonlocal blueshift and the plasmon linewidth are shown to be considerably affected by ensemble averaging. Size-variance effects tend however to conceal nonlocality to a lesser extent when the homogeneous size-dependent broadening of individual nanoparticles is taken into account, either through a local size-dependent damping model or through the Generalized Nonlocal Optical Response theory. The role of ensemble averaging is further explored in realistic distributions of isolated or weakly-interacting noble-metal nanoparticles, as encountered in experiments, while an analytical expression to evaluate the importance of inhomogeneous broadening through measurable quantities is developed. Our findings are independent of the specific nonclassical theory used, thus providing important insight into a large range of experiments on nanoscale and quantum plasmonics.
authors.affiliation: Technical University of Denmark, Department of Photonics Engineering, Kgs. Lyngby, 2800, Denmark.
authors.forename: Christos
authors.initials: C
authors.lastname: Tserkezis
authors.affiliation: Technical University of Denmark, Department of Photonics Engineering, Kgs. Lyngby, 2800, Denmark.
authors.forename: Johan R
authors.initials: JR
authors.lastname: Maack
authors.affiliation: University of California, San Diego, Department of Electrical and Computer Engineering, La Jolla, CA 92093-0407, USA.
authors.forename: Zhaowei
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Technical University of Denmark, Department of Photonics Engineering, Kgs. Lyngby, 2800, Denmark.|Technical University of Denmark, Center for Nanostructured Graphene, Kgs. Lyngby, 2800, Denmark.
authors.forename: Martijn
authors.initials: M
authors.lastname: Wubs
authors.affiliation: Technical University of Denmark, Department of Photonics Engineering, Kgs. Lyngby, 2800, Denmark.|Technical University of Denmark, Center for Nanostructured Graphene, Kgs. Lyngby, 2800, Denmark.
authors.forename: N Asger
authors.initials: NA
authors.lastname: Mortensen