12,080 research outputs found
Stochastic resonance with weak monochromatic driving: gains above unity induced by high-frequency signals
We study the effects of a high-frequency (HF) signal on the response of a
noisy bistable system to a low-frequency subthreshold sinusoidal signal. We
show that, by conveniently choosing the ratio of the amplitude of the HF signal
to its frequency, stochastic resonance gains greater than unity can be measured
at the low-frequency value. Thus, the addition of the HF signal can entail an
improvement in the detection of weak monochromatic signals. The results are
explained in terms of an effective model and illustrated by means of numerical
simulations.Comment: 5 pages, 2 figure
Hot carrier and hot phonon coupling during ultrafast relaxation of photoexcited electrons in graphene
We study, by means of a Monte Carlo simulator, the hot phonon effect on the
relaxation dynamics in photoexcited graphene and its quantitative impact as
compared to considering an equilibrium phonon distribution. Our multi-particle
approach indicates that neglecting the hot phonon effect significantly
underestimates the relaxation times in photoexcited graphene. The hot phonon
effect is more important for a higher energy of the excitation pulse and
photocarrier densities between and .
Acoustic intervalley phonons play a non-negligible role, and emitted phonons
with wavelengths limited up by a maximum (determined by the carrier
concentration) induce a slower carrier cooling rate. Intrinsic phonon heating
is damped in graphene on a substrate due to additional cooling pathways, with
the hot phonon effect showing a strong inverse dependence with the carrier
density.Comment: 12 pages, 5 figure
Statistical Mechanics of finite arrays of coupled bistable elements
We discuss the equilibrium of a single collective variable characterizing a
finite set of coupled, noisy, bistable systems as the noise strength, the size
and the coupling parameter are varied. We identify distinct regions in
parameter space. The results obtained in prior works in the asymptotic infinite
size limit are significantly different from the finite size results. A
procedure to construct approximate 1-dimensional Langevin equation is adopted.
This equation provides a useful tool to understand the collective behavior even
in the presence of an external driving force
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