370 research outputs found
Robustness of the Rabi splitting under nonlocal corrections in plexcitonics
We explore theoretically how nonlocal corrections in the description of the
metal affect the strong coupling between excitons and plasmons in typical
examples where nonlocal effects are anticipated to be strong, namely small
metallic nanoparticles, thin metallic nanoshells or dimers with narrow
separations, either coated with or encapsulating an excitonic layer. Through
detailed simulations based on the generalised nonlocal optical response theory,
which simultaneously accounts both for modal shifts due to screening and for
surface-enhanced Landau damping, we show that, contrary to expectations, the
influence of nonlocality is rather limited, as in most occasions the width of
the Rabi splitting remains largely unaffected and the two hybrid modes are well
distinguishable. We discuss how this behaviour can be understood in view of the
popular coupled-harmonic-oscillator model, while we also provide analytic
solutions based on Mie theory to describe the hybrid modes in the case of
matryoshka-like single nanoparticles. Our analysis provides an answer to a so
far open question, that of the influence of nonlocality on strong coupling, and
is expected to facilitate the design and study of plexcitonic architectures
with ultrafine geometrical details
How nonlocal damping reduces plasmon-enhanced fluorescence in ultranarrow gaps
The nonclassical modification of plasmon-assisted fluorescence enhancement is
theoretically explored by placing two-level dipole emitters at the narrow gaps
encountered in canonical plasmonic architectures, namely dimers and trimers of
different metallic nanoparticles. Through detailed simulations, in comparison
with appropriate analytical modelling, it is shown that within classical
electrodynamics, and for the reduced separations explored here, fluorescence
enhancement factors of the order of can be achieved, with a divergent
behaviour as the particle touching regime is approached. This remarkable
prediction is mainly governed by the dramatic increase in excitation rate
triggered by the corresponding field enhancement inside the gaps. Nevertheless,
once nonclassical corrections are included, the amplification factors decrease
by up to two orders of magnitude and a saturation regime for narrower gaps is
reached. These nonclassical limitations are demonstrated by simulations based
on the generalised nonlocal optical response theory, which accounts in an
efficient way not only for nonlocal screening, but also for the enhanced Landau
damping near the metal surface. A simple strategy to introduce nonlocal
corrections to the analytic solutions is also proposed. It is therefore shown
that the nonlocal optical response of the metal imposes more realistic, finite
upper bounds to the enhancement feasible with ultrasmall plasmonic cavities,
thus providing a theoretical description closer to state of the art
experiments
Surface-plasmon resonances of arbitrarily shaped nanometallic structures in the small-screening-length limit
According to the hydrodynamic Drude model, surface-plasmon resonances of
metallic nanostructures blueshift owing to the nonlocal response of the metal's
electron gas. The screening length characterising the nonlocal effect is often
small relative to the overall dimensions of the metallic structure, which
enables us to derive a coarse-grained nonlocal description using matched
asymptotic expansions; a perturbation theory for the blueshifts of arbitrary
shaped nanometallic structures is then developed. The effect of nonlocality is
not always a perturbation and we present a detailed analysis of the "bonding"
modes of a dimer of nearly touching nanowires where the leading-order
eigenfrequencies and eigenmode distributions are shown to be a renormalisation
of those predicted assuming a local metal permittivity
Scheme for preparation of W state via cavity QED
In this paper, we presented a physical scheme to generate the multi-cavity
maximally entangled W state via cavity QED. All the operations needed in this
scheme are to modulate the interaction time only once.Comment: 8 pages, 1 figur
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