5 research outputs found
Two-fluid hydrodynamic model for semiconductors
The hydrodynamic Drude model (HDM) has been successful in describing the
optical properties of metallic nanostructures, but for semiconductors where
several different kinds of charge carriers are present, an extended theory is
required. We present a two-fluid hydrodynamic model for semiconductors
containing electrons and holes (from thermal or external excitation) or light
and heavy holes (in -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 are able to 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.Comment: Accepted in PRB. 17 pages, 9 figures, 1 tabl
Hydrodynamic acoustic plasmon resonances in semiconductor nanowires and their dimers
The hydrodynamic Drude model known from metal plasmonics also applies to
semiconductor structures of sizes in between single-particle quantum
confinement and bulk. But contrary to metals, for semiconductors two or more
types of plasma may have to be taken into account in order to properly describe
their plasmonic properties. In this combined analytical and computational
study, we explore predictions of the recently proposed two-fluid hydrodynamic
Drude model for the optical properties of plasmonic semiconductor nanowires, in
particular for thermally excited InSb nanowires. We focus on the low-frequency
acoustic surface and bulk plasmon resonances that are unique fingerprints for
this model and are yet to be observed. We identify these resonances in spectra
for single nanowires based on analytical calculations, and they are in complete
agreement with our numerical implementation of the model. For dimers of
nanowires we predict substantial increase of the extinction cross section and
field enhancement of the acoustic localized surface plasmon resonance, which
makes its observation in dimers more likely.Comment: I would like to inform that Dr.Abbas Zarifi is the corresponding
author of this pape
Robustness of the far-field response of nonlocal plasmonic ensembles
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 (NPs) are therefore
expected to exhibit a nonclassical inhomogeneous spectral broadening due to
size distribution. For a normal distribution of free-electron NPs, and within
the simple nonlocal Hydrodynamic Drude Model (HDM), 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 NPs
is taken into account, either through a local size-dependent damping (SDD)
model or through the Generalized Nonlocal Optical Response (GNOR) theory. The
role of ensemble averaging is further explored in realistic distributions of
noble-metal NPs, 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
Plasmonic semiconductor nanoparticles showing nonlocal response
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