13,259 research outputs found
Theory of plasmon-enhanced high-harmonic generation in the vicinity of metal nanostructures in noble gases
We present a semiclassical model for plasmon-enhanced high-harmonic
generation (HHG) in the vicinity of metal nanostructures. We show that both the
inhomogeneity of the enhanced local fields and electron absorption by the metal
surface play an important role in the HHG process and lead to the generation of
even harmonics and to a significantly increased cutoff. For the examples of
silver-coated nanocones and bowtie antennas we predict that the required
intensity reduces by up to three orders of magnitudes and the HHG cutoff
increases by more than a factor of two. The study of the enhanced high-harmonic
generation is connected with a finite-element simulation of the electric field
enhancement due to the excitation of the plasmonic modes.Comment: 4 figure
On surface plasmon polariton wavepacket dynamics in metal-dielectric heterostructures
The WKB equations for dynamics of the surface plasmon polariton (SPP)
wavepacket are studied. The dispersion law for the SPP in the metal-dielectric
heterostructure with varying thickness of a perforated dielectric layer is
rigorously calculated and investigated using the scattering matrix method. Two
channels of the SPP wavepacket optical losses related to the absorption in a
metal and to the SPP leakage are analyzed. It is shown that change of the
dielectric layer thickness acts on the SPP as an external force leading to
evolution of its quasimomentum and to the wavepacket reversal or even to the
optical Bloch oscillations (BO). Properties of these phenomena are investigated
and discussed. Typical values of the BO amplitude are about tens of microns and
the period is around tens or hundreds of femtoseconds.Comment: 12 pages, 5 figure
Noise-Activated Escape from a Sloshing Potential Well
We treat the noise-activated escape from a one-dimensional potential well of
an overdamped particle, to which a periodic force of fixed frequency is
applied. We determine the boundary layer behavior, and the physically relevant
length scales, near the oscillating well top. We show how stochastic behavior
near the well top generalizes the behavior first determined by Kramers, in the
case without forcing. Both the case when the forcing dies away in the weak
noise limit, and the case when it does not, are examined. We also discuss the
relevance of various scaling regimes to recent optical trap experiments.Comment: 9 pages, no figures, REVTeX, expanded versio
Pairing symmetry of the one-band Hubbard model in the paramagnetic weak-coupling limit: a numerical RPA study
We study the spin-fluctuation-mediated superconducting pairing gap in a
weak-coupling approach to the Hubbard model for a two dimensional square
lattice in the paramagnetic state. Performing a comprehensive theoretical study
of the phase diagram as a function of filling, we find that the superconducting
gap exhibits transitions from p-wave at very low electron fillings to
d_{x^2-y^2}-wave symmetry close to half filling in agreement with previous
reports. At intermediate filling levels, different gap symmetries appear as a
consequence of the changes in the Fermi surface topology and the associated
structure of the spin susceptibility. In particular, the vicinity of a van Hove
singularity in the electronic structure close to the Fermi level has important
consequences for the gap structure in favoring the otherwise sub-dominant
triplet solution over the singlet d-wave solution. By solving the full gap
equation, we find that the energetically favorable triplet solutions are chiral
and break time reversal symmetry. Finally, we also calculate the detailed
angular gap structure of the quasi-particle spectrum, and show how
spin-fluctuation-mediated pairing leads to significant deviations from the
first harmonics both in the singlet d_{x^2-y^2} gap as well as the chiral
triplet gap solution.Comment: 11 pages 11 figure
Recommended from our members
Integration with Ontologies
One of today’s hottest IT topics is integration, as bringing together information from different sources and structures is not completely solved. The approach outlined here wants to illustrate how ontologies [Gr93] could help to support the integration process
Phase behavior of the Confined Lebwohl-Lasher Model
The phase behavior of confined nematogens is studied using the Lebwohl-Lasher
model. For three dimensional systems the model is known to exhibit a
discontinuous nematic-isotropic phase transition, whereas the corresponding two
dimensional systems apparently show a continuous
Berezinskii-Kosterlitz-Thouless like transition. In this paper we study the
phase transitions of the Lebwohl-Lasher model when confined between planar
slits of different widths in order to establish the behavior of intermediate
situations between the pure planar model and the three-dimensional system, and
compare with previous estimates for the critical thickness, i.e. the slit width
at which the transition switches from continuous to discontinuous.Comment: Submitted to Physical Review
Monadic Functional Reactive Programming
Functional Reactive Programming (FRP) is a way to program reactive systems in functional style, eliminating many of the problems
that arise from imperative techniques. In this paper, we present an
alternative FRP formulation that is based on the notion of a reactive computation: a monadic computation which may require the
occurrence of external events to continue. A signal computation is a
reactive computation that may also emit values. In contrast to signals
in other FRP formulations, signal computations can end, leading to
a monadic interface for sequencing signal phases. This interface has
several advantages: routing is implicit, sequencing signal phases is
easier and more intuitive than when using the switching combinators found in other FRP approaches, and dynamic lists require much
less boilerplate code. In other FRP approaches, either the entire
FRP expression is re-evaluated on each external stimulus, or impure
techniques are used to prevent redundant re-computations. We show
how Monadic FRP can be implemented straightforwardly in a purely
functional way while preventing redundant re-computations
Off-resonance field enhancement by spherical nanoshells
We study light scattering by spherical nanoshells consistent of
metal/dielectric composites. We consider two geometries of metallic nanoshell
with dielectric core, and dielectric coated metallic nanoparticle. We
demonstrate that for both geometries the local field enhancement takes place
out of resonance regions ("dark states"), which, nevertheless, can be
understood in terms of the Fano resonance. At optimal conditions the light is
stronger enhanced inside the dielectric material. By using nonlinear dielectric
materials it will lead to a variety nonlinear phenomena applicable for
photonics applications
Dynamics of higher-order solitons in regular and PT-symmetric nonlinear couplers
Dynamics of symmetric and antisymmetric 2-solitons and 3-solitons is studied
in the model of the nonlinear dual-core coupler and its PT-symmetric version.
Regions of the convergence of the injected perturbed symmetric and
antisymmetric N-solitons into symmetric and asymmetric quasi-solitons are
found. In the PT-symmetric system, with the balanced gain and loss acting in
the two cores, borders of the stability against the blowup are identified.
Notably, in all the cases the stability regions are larger for antisymmetric
2-soliton inputs than for their symmetric counterparts, on the contrary to
previously known results for fundamental solitons (N=1). Dynamical regimes
(switching) are also studied for the 2-soliton injected into a single core of
the coupler. In particular, a region of splitting of the input into a pair of
symmetric solitons is found, which is explained as a manifestation of the
resonance between the vibrations of the 2-soliton and oscillations of energy
between the two cores in the coupler.Comment: To appear in EPL journa
Plasmonic crystals for ultrafast nanophotonics: Optical switching of surface plasmon polaritons
We demonstrate that the dispersion of surface plasmon polaritons in a
periodically perforated gold film can be efficiently manipulated by femtosecond
laser pulses with the wavelengths far from the intrinsic resonances of gold.
Using a time- and frequency- resolved pump-probe technique we observe shifting
of the plasmon polariton resonances with response times from 200 to 800 fs
depending on the probe photon energy, through which we obtain comprehensive
insight into the electron dynamics in gold. We show that Wood anomalies in the
optical spectra provide pronounced resonances in differential transmission and
reflection with magnitudes up to 3% for moderate pump fluences of 0.5 mJ/cm^2.Comment: 5 pages, 4 figure
- …