Plasmonic semiconductor nanoparticles showing nonlocal response

Abstract

We predict that localized surface plasmons (LSP) in semiconductor particles exhibit spatial nonlocal response effects as the geometry enters the nanometer scale. To investigate these nonlocal effects, we first apply the hydrodynamic model (HDM) to nanospheres of two different semiconductor materials: intrinsic InSb and n-doped GaAs. Our results show that the semiconductors indeed display nonlocal effects, and that these effects are even more pronounced than in metals, and more tunable as well. We also present a two-fluid hydrodynamic model for semiconductors containing electrons and holes (from thermal or external excitation) or light and heavy holes (in p-doped materials). The two-fluid model predicts the existence of two longitudinal modes, an acoustic and an optical, whereas only an optical mode is present in the HDM. By extending nonlocal Mie theory to two plasmas, we simulate the optical properties of two-fluid nanospheres and predict that the acoustic mode gives rise to peaks in the extinction spectra that are absent in the HDM. And from a numerical study, we predict that by considering dimers rather than monomers of nanowires, the extinction cross section and field enhancement of the acoustic localized surface plasmon resonances can increase substantially. In this conference proceedings, we present calculations of the two-fluid GNOR model, which show that acoustic surface plasmon modes are surprisingly robust against size-dependent broadening.