707 research outputs found
Size-dependent nonlocal effects in plasmonic semiconductor particles
Localized surface plasmons (LSP) in semiconductor particles are expected to
exhibit spatial nonlocal response effects as the geometry enters the nanometer
scale. To investigate these nonlocal effects, we apply the hydrodynamic model
to nanospheres of two different semiconductor materials: intrinsic InSb and
-doped GaAs. Our results show that the semiconductors indeed display
nonlocal effects, and that these effects are even more pronounced than in
metals. In a InSb particle at , the LSP
frequency is blueshifted 35%, which is orders of magnitude larger than the
blueshift in a metal particle of the same size. This property, together with
their tunability, makes semiconductors a promising platform for experiments in
nonlocal effects.Comment: 7 pages, 3 figures, 1 table, corrected typos in text and figure
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
Nonequilibrium orientational patterns in two-component Langmuir monolayers
A model of a phase-separating two-component Langmuir monolayer in the
presence of a photo-induced reaction interconvering two components is
formulated. An interplay between phase separation, orientational ordering and
treaction is found to lead to a variety of nonequilibrium self-organized
patterns, both stationary and traveling. Examples of the patterns, observed in
numerical simulations, include flowing droplets, traveling stripes, wave
sources and vortex defects.Comment: Submitted to the Physical Review
Long-term exposure to environmental concentrations of the pharmaceutical ethynylestradiol causes reproductive failure in fish
International audienceHeightened concern over endocrine-disrupting chemicals is driven by the hypothesis that they could reduce reproductive success and affect wildlife populations, but there is little evidence for this expectation. The pharmaceutical ethynylestradiol (EE(2)) is a potent endocrine modulator and is present in the aquatic environment at biologically active concentrations. To investigate impacts on reproductive success and mechanisms of disruption, we exposed breeding populations (n = 12) of zebrafish (Danio rerio) over multiple generations to environmentally relevant concentrations of EE(2). Life-long exposure to 5 ng/L EE(2) in the F, generation caused a 56% reduction in fecundity and complete population failure with no fertilization. Conversely, the same level of exposure for up to 40 days in mature adults in the parental F(0) generation had no impact on reproductive success. Infertility in the F, generation after life-long exposure to 5 ng/L EE(2) was due to disturbed sexual differentiation, with males having no functional testes and either undifferentiated or intersex gonads. These F, males also showed a reduced vitellogenic response when compared with F(0) males, indicating an acclimation to EE(2) exposure. Deputation studies found only a partial recovery in reproductive capacity after 5 months. Significantly, even though the F(0) males lacked functional testes, they showed male-pattern reproductive behavior, inducing the spawning act and competing with healthy males to disrupt fertilization. Endocrine disruption is therefore likely to affect breeding dynamics and reproductive success in group-spawning fish. Our findings raise major concerns about the population-level impacts for wildlife of long-term exposure to low concentrations of estrogenic endocrine disruptors
From Women-Staffed to Women-Led: Gender and Leadership in Academic Libraries, 1974-2018.
This article reviews post-1974 scholarly literature on women’s leadership in academic libraries, with the emphasis on the United States. The purpose of this synthesis is to highlight research areas and themes that have significantly expanded the profession’s knowledge about gender and its impact at the top administrative level. The article starts with a brief overview of theories of gender and leadership before tracing scholarship on the gendered career patterns singled out in Schiller’s work (1974). The article then focuses on additional issues related to gender and library administration, including leadership styles, perceptions of differences between male and female leaders, and the lack of diversity among academic library women directors
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