5,597 research outputs found
Mechanism of Near-Field Raman Enhancement in One-Dimensional Systems
We develop a theory of near-field Raman enhancement in one-dimensional systems, and report supporting experimental results for carbon nanotubes. The enhancement is established by a laser-irradiated nanoplasmonic structure acting as an optical antenna. The near-field Raman intensity is inversely proportional to the 10th power of the separation between the enhancing structure and the one-dimensional system. Experimental data obtained from single-wall carbon nanotubes indicate that the Raman enhancement process is not significantly influenced by the specific phonon eigenvector, and is mainly defined by the properties of the nanoplasmonic structure
Comment on "Dynamic properties in a family of competitive growing models"
The article [Phys. Rev. E {\bf 73}, 031111 (2006)] by Horowitz and Albano
reports on simulations of competitive surface-growth models RD+X that combine
random deposition (RD) with another deposition X that occurs with probability
. The claim is made that at saturation the surface width obeys a
power-law scaling , where is only either
or , which is illustrated by the models where X is
ballistic deposition and where X is RD with surface relaxation. Another claim
is that in the limit , for any lattice size , the time evolution
of generally obeys the scaling , where is Family-Vicsek universal scaling function. We
show that these claims are incorrect.Comment: 2 pages, 3 figures, accepted for publication in Physical Review E in
Aug. 200
Extreme Long-time Dynamic Monte Carlo Simulations
We study the extreme long-time behavior of the metastable phase of the
three-dimensional Ising model with Glauber dynamics in an applied magnetic
field and at a temperature below the critical temperature. For these
simulations we use the advanced simulation method of projective dynamics. The
algorithm is described in detail, together with its application to the escape
from the metastable state. Our results for the field dependence of the
metastable lifetime are in good agreement with theoretical expectations and
span more than fifty decades in time.Comment: 13 pages with embedded eps figures. Int. J. Mod. Phys. C, in pres
Sub-Kelvin Parametric Feedback Cooling of a Laser-Trapped Nanoparticle
Recent experiments have demonstrated the ability to optically cool a
macroscopic mechanical oscillator to its quantum ground state by means of
dynamic backaction. Such experiments allow quantum mechanics to be tested with
mesoscopic objects, and represent an essential step toward quantum optical
memories, transducers, and amplifiers. Most oscillators considered so far are
rigidly connected to their thermal environment, fundamentally limiting their
mechanical Q-factors and requiring cryogenic precooling to liquid helium
temperatures. Here we demonstrate parametric feedback cooling of a
laser-trapped nanoparticle which is entirely isolated from the thermal bath.
The lack of a clamping mechanism provides robust decoupling from internal
vibrations and makes it possible to cool the nanoparticle in all degrees of
freedom by means of a single laser beam. Compared to laser-trapped
microspheres, nanoparticles have the advantage of higher resonance frequencies
and lower recoil heating, which are favorable conditions for quantum ground
state coolin
A projection method for statics and dynamics of lattice spin systems
A method based on Monte Carlo sampling of the probability flows projected
onto the subspace of one or more slow variables is proposed for investigation
of dynamic and static properties of lattice spin systems. We illustrate the
method by applying it, with projection onto the order-parameter subspace, to
the three-dimensional 3-state Potts model in equilibrium and to metastable
decay in a three-dimensional 3-state kinetic Potts model.Comment: 4 pages, 3 figures, RevTex, final version to appear in Phys. Rev.
Let
Scanning emitter lifetime imaging microscopy for spontaneous emission control
We report an experimental technique to map and exploit the local density of
optical states of arbitrary planar nano-photonic structures. The method relies
on positioning a spontaneous emitter attached to a scanning probe
deterministically and reversibly with respect to its photonic environment while
measuring its lifetime. We demonstrate the method by imaging the enhancement of
the local density of optical states around metal nanowires. By
nano-positioning, the decay rate of a pointlike source of fluorescence can be
reversibly and repeatedly changed by a factor of two by coupling it to the
guided plasmonic mode of the wire
Universal Scaling in Mixing Correlated Growth with Randomness
We study two-component growth that mixes random deposition (RD) with a
correlated growth process that occurs with probability p. We find that these
composite systems are in the universality class of the correlated growth
process. For RD blends with either Edwards-Wilkinson of Kardar-Parisi-Zhang
processes, we identify a nonuniversal parameter in the universal scaling in p.Comment: 4 pages, 6 figures, 11 references; under revie
Plasmon-mediated superradiance near metal nanostructures
We develop a theory of cooperative emission of light by an ensemble of
emitters, such as fluorescing molecules or semiconductor quantum dots, located
near a metal nanostructure supporting surface plasmon. The primary mechanism of
cooperative emission in such systems is resonant energy transfer between
emitters and plasmons rather than the Dicke radiative coupling between
emitters. We identify two types of plasmonic coupling between the emitters, (i)
plasmon-enhanced radiative coupling and (ii) plasmon-assisted nonradiative
energy transfer, the competition between them governing the structure of system
eigenstates. Specifically, when emitters are removed by more than several nm
from the metal surface, the emission is dominated by three superradiant states
with the same quantum yield as a single emitter, resulting in a drastic
reduction of ensemble radiated energy, while at smaller distances cooperative
behavior is destroyed by nonradiative transitions. The crossover between two
regimes can be observed in distance dependence of ensemble quantum efficiency.
Our numerical calculations incorporating direct and plasmon-assisted
interactions between the emitters indicate that they do not destroy the
plasmonic Dicke effect.Comment: 12 pages, 10 figure
Calculation of the Raman G peak intensity in monolayer graphene: role of Ward identities
The absolute integrated intensity of the single-phonon Raman peak at 1580
cm^{-1} is calculated for a clean graphene monolayer. The resulting intensity
is determined by the trigonal warping of the electronic bands and the
anisotropy of the electron-phonon coupling, and is proportional to the second
power of the excitation frequency. The main contribution to the process comes
from the intermediate electron-hole states with typical energies of the order
of the excitation frequency, contrary to what has been reported earlier. This
occurs because of strong cancellations between different terms of the
perturbation theory, analogous to Ward identities in quantum electrodynamics
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