70 research outputs found
Long lived matter waves Bloch oscillations and dynamical localization by time dependent nonlinearity management
We introduce a new method to achieve long lived Bloch oscillations and
dynamical localization of matter wave gap solitons in optical lattices. The
method is based on time dependent modulations of the nonlinearity which can be
experimentally implemented by means of the Feshbach resonance technique. In
particular, we show that the width of the wave packet is preserved if time
modulations of the nonlinearity are taken proportional to the curvature of the
linear band spectrum which for most typical experimental settings are well
approximated by harmonic time modulations of proper frequencies
Dynamical localization of gap-solitons by time periodic forces
The phenomenon of dynamical localization of matter wave solitons in optical
lattices is first demonstrated and the conditions for its existence are
discussed. In addition to the trapping linear periodic potential we use a
periodic modulation of the nonlinearity in space to eliminate nonexistence
regions of gap-solitons in reciprocal space. We show that when this condition
is achieved, the observation of dynamical localization in true nonlinear regime
becomes possible. The results apply to all systems described by the periodic
nonlinear Schr\"odinger equation, including Bose-Einstein condensates of
ultracold atoms trapped in optical lattices and arrays of waveguides or
photonic crystals in nonlinear optics.Comment: accepted for Europhysics Letter
Localized modes in arrays of boson-fermion mixtures
It is shown that the mean-field description of a boson-fermion mixture with a
dominating fermionic component, loaded in a one-dimensional optical lattice, is
reduced to the nonlinear Schr\"{o}dinger equation with a periodic potential and
periodic nonlinearity. In such system there exist localized modes having
peculiar properties. In particular, for some regions of parameters there exists
a lower bound for a number of atoms necessary for creation of a mode, while for
other domains small amplitude gap solitons are not available in vicinity of
either of the gap edges. We found that the lowest branch of the symmetric
solution may either exist only for a restricted range of energies in a gap or
does not exist, unlike in pure bosonic condensates. The simplest bifurcations
of the modes are shown and stability of the modes is verified numerically
Surface modes and breathers in finite arrays of nonlinear waveguides
We present the complete set of symmetric and antisymmetric (edge and corner)
surface modes in finite one-- and two--dimensional arrays of waveguides. We
provide classification of the modes based on the anti-continuum limit, study
their stability and bifurcations, and discuss relation between surface and bulk
modes. We put forward existence of surface breathers, which represent
two-frequency modes localized about the array edges.Comment: Accepted for publication in Physical Review
Light scattering by a medium with a spatially modulated optical conductivity: the case of graphene
We describe light scattering from a graphene sheet having a modulated optical
conductivity. We show that such modulation enables the excitation of surface
plasmon-polaritons by an electromagnetic wave impinging at normal incidence.
The resulting surface plasmon-polaritons are responsible for a substantial
increase of electromagnetic radiation absorption by the graphene sheet. The
origin of the modulation can be due either to a periodic strain field or to
adatoms (or absorbed molecules) with a modulated adsorption profile.Comment: http://iopscience.iop.org/0953-8984/24/24/24530
Rabi oscillations of matter wave solitons in optical lattices
Inter-band Rabi oscillations of gap soliton matter waves induced by time
dependent periodic forces in combined linear and nonlinear optical lattices are
for the first time demonstrated. It is shown that under suitable conditions
these oscillations can become long-lived. By switching off the external force
at proper time it is possible to create either pure (stationary macroscopically
populated) gap soliton states or linear combination of two gap solitons with
appreciably long life-time
Acceleration and localization of matter in a ring trap
A toroidal trap combined with external time-dependent electric field can be
used for implementing different dynamical regimes of matter waves. In
particular, we show that dynamical and stochastic acceleration, localization
and implementation of the Kapitza pendulum can be originated by means of proper
choice of the external force
Mechanism for graphene-based optoelectronic switches by tuning surface plasmon-polaritons in monolayer graphene
It is shown that one can explore the optical conductivity of graphene,
together with the ability of controlling its electronic density by an applied
gate voltage, in order to achieve resonant coupling between an external
electromagnetic radiation and surface plasmon-polaritons in the graphene layer.
This opens the possibility of electrical control of the intensity of light
reflected inside a prism placed on top of the graphene layer, by switching
between the regimes of total reflection and total absorption. The predicted
effect can be used to build graphene-based opto-electronic switches.Comment: 5 page
Graphene-based polaritonic crystal
It is shown that monolayer graphene deposited on a spatially-periodic gate
behaves as a polaritonic crystal. Its band structure depending on the applied
gate voltage is studied. The scattering of electromagnetic radiation from such
a crystal is presented calculated and analyzed in terms of Fano-type resonances
between the reflected continuum and plasmon-polariton modes forming narrow
bands.Comment: submitted to Phys. Rev. Let
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