5,363 research outputs found
Ab initio theory of Fano resonances in plasmonic nanostructures and metamaterials
An ab initio theory for Fano resonances in plasmonic nanostructures and
metamaterials is developed using Feshbach formalism. It reveals the role played
by the electromagnetic modes and material losses in the system, and enables the
engineering of Fano resonances in arbitrary geometries. A general formula for
the asymmetric resonance in a non-conservative system is derived. The influence
of the electromagnetic interactions on the resonance line shape is discussed
and it is shown that intrinsic losses drive the resonance contrast, while its
width is mostly determined by the coupling strength between the non-radiative
mode and the continuum. The analytical model is in perfect agreement with
numerical simulations.Comment: 13 pages, 5 figure
Low-temperature nucleation in a kinetic Ising model with soft stochastic dynamics
We study low-temperature nucleation in kinetic Ising models by analytical and
simulational methods, confirming the general result for the average metastable
lifetime, = A*exp(beta*Gamma) (beta = 1/kT) [E. Jordao Neves and R.H.
Schonmann, Commun. Math. Phys. 137, 209 (1991)]. Contrary to common belief, we
find that both A and Gamma depend significantly on the stochastic dynamic. In
particular, for a ``soft'' dynamic, in which the effects of the interactions
and the applied field factorize in the transition rates, Gamma does NOT simply
equal the energy barrier against nucleation, as it does for the standard
Glauber dynamic, which does not have this factorization property.Comment: 4 pages RevTex4, 2 figures. Phys. Rev. Lett., in pres
Real-Time Description of the Electronic Dynamics for a Molecule close to a Plasmonic Nanoparticle
The optical properties of molecules close to plasmonic nanostructures greatly
differ from their isolated molecule counterparts. To theoretically investigate
such systems in a Quantum Chemistry perspective, one has to take into account
that the plasmonic nanostructure (e.g., a metal nanoparticle - NP) is often too
large to be treated atomistically. Therefore, a multiscale description, where
the molecule is treated by an ab initio approach and the metal NP by a lower
level description, is needed. Here we present an extension of one such
multiscale model [Corni, S.; Tomasi, J. {\it J. Chem. Phys.} {\bf 2001}, {\it
114}, 3739] originally inspired by the Polarizable Continuum Model, to a
real-time description of the electronic dynamics of the molecule and of the NP.
In particular, we adopt a Time-Dependent Configuration Interaction (TD CI)
approach for the molecule, the metal NP is described as a continuous dielectric
of complex shape characterized by a Drude-Lorentz dielectric function and the
molecule- NP electromagnetic coupling is treated by an equation-of-motion (EOM)
extension of the quasi-static Boundary Element Method (BEM). The model includes
the effects of both the mutual molecule- NP time-dependent polarization and the
modification of the probing electromagnetic field due to the plasmonic
resonances of the NP. Finally, such an approach is applied to the investigation
of the light absorption of a model chromophore, LiCN, in the presence of a
metal NP of complex shape.Comment: This is the final peer-reviewed manuscript accepted for publication
of an open access article published under an ACS AuthorChoice License, which
permits copying and redistribution of the article or any adaptations for
non-commercial purposes. Link to the original article:
http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.6b1108
Universal oscillations in counting statistics
Noise is a result of stochastic processes that originate from quantum or
classical sources. Higher-order cumulants of the probability distribution
underlying the stochastic events are believed to contain details that
characterize the correlations within a given noise source and its interaction
with the environment, but they are often difficult to measure. Here we report
measurements of the transient cumulants > of the number n of passed
charges to very high orders (up to m=15) for electron transport through a
quantum dot. For large m, the cumulants display striking oscillations as
functions of measurement time with magnitudes that grow factorially with m.
Using mathematical properties of high-order derivatives in the complex plane we
show that the oscillations of the cumulants in fact constitute a universal
phenomenon, appearing as functions of almost any parameter, including time in
the transient regime. These ubiquitous oscillations and the factorial growth
are system-independent and our theory provides a unified interpretation of
previous theoretical studies of high-order cumulants as well as our new
experimental data.Comment: 19 pages, 4 figures, final version as published in PNA
Remote optical addressing of single nano-objects
We present a scheme for remotely addressing single nano-objects by means of
near-field optical microscopy that makes only use of one of the most
fundamental properties of electromagnetic radiation: its polarization. A medium
containing optically active nano-objects is covered with a thin metallic film
presenting sub-wavelength holes. When the optical tip is positioned some
distance away from a hole, surface plasmons in the metal coating are generated
which, by turning the polarization plane of the excitation light, transfer the
excitation towards a chosen hole and induce emission from the underlying
nano-objects. The method, easily applicable to other systems, is demonstrated
for single quantum dots (QDs) at low temperature. It may become a valuable tool
for future optical applications in the nanoworld
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