11,237 research outputs found
Dynamics of an electron in finite and infinite one dimensional systems in presence of electric field
We study,numerically, the dynamical behavior of an electron in a two site
nonlinear system driven by dc and ac electric field separately. We also study,
numerically, the effect of electric field on single static impurity and
antidimeric dynamical impurity in an infinite 1D chain to find the strength of
the impurities. Analytical arguments for this system have also been given.Comment: File Latex, 8 Figures available on reques
Chaotic Phenomenon in Nonlinear Gyrotropic Medium
Nonlinear gyrotropic medium is a medium, whose natural optical activity
depends on the intensity of the incident light wave. The Kuhn's model is used
to study nonlinear gyrotropic medium with great success. The Kuhn's model
presents itself a model of nonlinear coupled oscillators. This article is
devoted to the study of the Kuhn's nonlinear model. In the first paragraph of
the paper we study classical dynamics in case of weak as well as strong
nonlinearity. In case of week nonlinearity we have obtained the analytical
solutions, which are in good agreement with the numerical solutions. In case of
strong nonlinearity we have determined the values of those parameters for which
chaos is formed in the system under study. The second paragraph of the paper
refers to the question of the Kuhn's model integrability. It is shown, that at
the certain values of the interaction potential this model is exactly
integrable and under certain conditions it is reduced to so-called universal
Hamiltonian. The third paragraph of the paper is devoted to quantum-mechanical
consideration. It shows the possibility of stochastic absorption of external
field energy by nonlinear gyrotropic medium. The last forth paragraph of the
paper is devoted to generalization of the Kuhn's model for infinite chain of
interacting oscillators
Stochastic resonance in soft matter systems: combined effects of static and dynamic disorder
We study the impact of static and dynamic disorder on the phenomenon of
stochastic resonance (SR) in a representative soft matter system. Due to their
extreme susceptibility to weak perturbations soft matter systems appear to be
excellent candidates for the observation of SR. Indeed, we derive generic SR
equations from a polymer stabilized ferroelectric liquid crystal (LC) cell,
which is a typical soft matter representative constituting one of the basic
components in several electro-optic applications. We generalize these equations
further in order to study an even broader class of qualitatively different
systems, especially disclosing the influence of different types of static
disorder and interaction ranges amongst LC molecules on the SR response. We
determine the required conditions for the observation of SR in the examined
system, and moreover, reveal that a random field type static disorder yields
qualitatively different responses with respect to random dilution, random bond
and spin glass universality classes. In particular, while the latter three
decrease the level of dynamic disorder (Gaussian noise) warranting the optimal
response, the former evokes exactly the opposite effect, hence increasing the
optimal noise level that is needed to resonantly fine-tune the system's
response in accordance with the weak deterministic electric field. These
observations are shown to be independent of the system size and range of
interactions, thus implying their general validity and potentially wide
applicability also within other similar settings. We argue that soft matter
systems might be particularly adequate as a base for different SR-based
sensitive detectors and thus potent candidates for additional theoretical as
well as experimental research in the presently outlined direction.Comment: 11 two-column pages, 6 figures; accepted for publication in Soft
Matte
Duffing revisited: Phase-shift control and internal resonance in self-sustained oscillators
We address two aspects of the dynamics of the forced Duffing oscillator which
are relevant to the technology of micromechanical devices and, at the same
time, have intrinsic significance to the field of nonlinear oscillating
systems. First, we study the stability of periodic motion when the phase shift
between the external force and the oscillation is controlled -contrary to the
standard case, where the control parameter is the frequency of the force.
Phase-shift control is the operational configuration under which self-sustained
oscillators -and, in particular, micromechanical oscillators- provide a
frequency reference useful for time keeping. We show that, contrary to the
standard forced Duffing oscillator, under phase-shift control oscillations are
stable over the whole resonance curve. Second, we analyze a model for the
internal resonance between the main Duffing oscillation mode and a
higher-harmonic mode of a vibrating solid bar clamped at its two ends. We focus
on the stabilization of the oscillation frequency when the resonance takes
place, and present preliminary experimental results that illustrate the
phenomenon. This synchronization process has been proposed to counteract the
undesirable frequency-amplitude interdependence in nonlinear time-keeping
micromechanical devices
Dynamically Generated Synthetic Electric Fields for Photons
Static synthetic magnetic fields give rise to phenomena including the Lorentz
force and the quantum Hall effect even for neutral particles, and they have by
now been implemented in a variety of physical systems. Moving towards fully
dynamical synthetic gauge fields allows, in addition, for backaction of the
particles' motion onto the field. If this results in a time-dependent vector
potential, conventional electromagnetism predicts the generation of an electric
field. Here, we show how synthetic electric fields for photons arise
self-consistently due to the nonlinear dynamics in a driven system. Our
analysis is based on optomechanical arrays, where dynamical gauge fields arise
naturally from phonon-assisted photon tunneling. We study open, one-dimensional
arrays, where synthetic magnetic fields are absent. However, we show that
synthetic electric fields can be generated dynamically, which, importantly,
suppress photon transport in the array. The generation of these fields depends
on the direction of photon propagation, leading to a novel mechanism for a
photon diode, inducing nonlinear nonreciprocal transport via dynamical
synthetic gauge fields.Comment: 12 pages, 5 figures; Fig. 2 and Fig. 3 modified in v2; paragraph "The
basic physics behind our results" added in v2; revised introduction including
new references in v3; Fig. 1 modified in v3; extended supplementary material
in v
Contribution of the magnetic resonance to the third harmonic generation from a fishnet metamaterial
We investigate experimentally and theoretically the third harmonic generated
by a double-layer fishnet metamaterial. To unambiguously disclose most notably
the influence of the magnetic resonance, the generated third harmonic was
measured as a function of the angle of incidence. It is shown experimentally
and numerically that when the magnetic resonance is excited by pump beam, the
angular dependence of the third harmonic signal has a local maximum at an
incidence angle of {\theta} \simeq 20{\deg}. This maximum is shown to be a
fingerprint of the antisymmetric distribution of currents in the gold layers.
An analytical model based on the nonlinear dynamics of the electrons inside the
gold shows excellent agreement with experimental and numerical results. This
clearly indicates the difference in the third harmonic angular pattern at
electric and magnetic resonances of the metamaterial.Comment: 7 pages, 5 figure
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