2,290 research outputs found
AC Josephson properties of phase slip lines in wide tin films
Current steps in the current-voltage characteristics of wide superconducting
Sn films exposed to a microwave irradiation were observed in the resistive
state with phase slip lines. The behaviour of the magnitude of the steps on the
applied irradiation power was found to be similar to that for the current steps
in narrow superconducting channels with phase slip centers and, to some extent,
for the Shapiro steps in Josephson junctions. This provides evidence for the
Josephson properties of the phase slip lines in wide superconducting films and
supports the assumption about similarity between the processes of phase slip in
wide and narrow films.Comment: 7 pages, 2 figures, to be published in Supercond. Sci. Techno
Effects of frequency correlation in linear optical entangling gate operated with independent photons
Bose-Einstein coalescence of independent photons at the surface of a beam
splitter is the physical process that allows linear optical quantum gates to be
built. When distinct parametric down-conversion events are used as an
independent photon source, distinguishability arises form the energy
correlation of each photon with its twin. We find that increasing the pump
bandwidth may help in improving the visibility of non-classical interference
and reaching a level of near perfect indistinguishability. PACS: 03.67.Mn,
42.65.Lm, 42.50.St.Comment: Replaced with published versio
Compressibility of a 2D electron gas under microwave radiation
Microwave irradiation of a two-dimensional electron gas (2DEG) produces a
non-equilibrium distribution of electrons, and leads to oscillations in the
dissipative part of the conductivity. We show that the same non-equilibrium
electron distribution induces strong oscillations in the 2DEG compressibility
measured by local probes. Local measurements of the compressibility are
expected to provide information about the domain structure of the zero
resistance state of a 2DEG under microwave radiation.Comment: v2: analysis of the wave-vector dependence of the compressibility
added; discussion of the Hall conductivity removed (shifted to
cond-mat/0409590 in a revised form
Random anisotropy disorder in superfluid 3He-A in aerogel
The anisotropic superfluid 3He-A in aerogel provides an interesting example
of a system with continuous symmetry in the presence of random anisotropy
disorder. Recent NMR experiments allow us to discuss two regimes of the
orientational disorder, which have different NMR properties. One of them, the
(s)-state, is identified as the pure Larkin-Imry-Ma state. The structure of
another state, the (f)-state, is not very clear: probably it is the
Larkin-Imry-Ma state contaminated by the network of the topological defects
pinned by aerogel.Comment: JETP Lett. style, 6 pages, no figures, discussion extended,
references added, version to be published in JETP Letter
Properties of discrete breathers in graphane from ab initio simulations
A density functional theory (DFT) study of the discrete breathers (DBs) in
graphane (fully hydrogenated graphene) was performed. To the best of our
knowledge, this is the first demonstration of the existence of DBs in a
crystalline body from the first-principle simulations. It is found that the DB
is a robust, highly localized vibrational mode with one hydrogen atom
oscillating with a large amplitude along the direction normal to the graphane
plane with all neighboring atoms having much smaller vibration amplitudes. DB
frequency decreases with increase in its amplitude, and it can take any value
within the phonon gap and can even enter the low-frequency phonon band. The
concept of DB is then used to propose an explanation to the recent experimental
results on the nontrivial kinetics of graphane dehydrogenation at elevated
temperatures.Comment: 20.07.14 Submitted to PhysRev
Translationally invariant nonlinear Schrodinger lattices
Persistence of stationary and traveling single-humped localized solutions in
the spatial discretizations of the nonlinear Schrodinger (NLS) equation is
addressed. The discrete NLS equation with the most general cubic polynomial
function is considered. Constraints on the nonlinear function are found from
the condition that the second-order difference equation for stationary
solutions can be reduced to the first-order difference map. The discrete NLS
equation with such an exceptional nonlinear function is shown to have a
conserved momentum but admits no standard Hamiltonian structure. It is proved
that the reduction to the first-order difference map gives a sufficient
condition for existence of translationally invariant single-humped stationary
solutions and a necessary condition for existence of single-humped traveling
solutions. Other constraints on the nonlinear function are found from the
condition that the differential advance-delay equation for traveling solutions
admits a reduction to an integrable normal form given by a third-order
differential equation. This reduction also gives a necessary condition for
existence of single-humped traveling solutions. The nonlinear function which
admits both reductions defines a two-parameter family of discrete NLS equations
which generalizes the integrable Ablowitz--Ladik lattice.Comment: 24 pages, 4 figure
Radiationless energy exchange in three-soliton collisions
We revisit the problem of the three-soliton collisions in the weakly
perturbed sine-Gordon equation and develop an effective three-particle model
allowing to explain many interesting features observed in numerical simulations
of the soliton collisions. In particular, we explain why collisions between two
kinks and one antikink are observed to be practically elastic or strongly
inelastic depending on relative initial positions of the kinks. The fact that
the three-soliton collisions become more elastic with an increase in the
collision velocity also becomes clear in the framework of the three-particle
model. The three-particle model does not involve internal modes of the kinks,
but it gives a qualitative description to all the effects observed in the
three-soliton collisions, including the fractal scattering and the existence of
short-lived three-soliton bound states. The radiationless energy exchange
between the colliding solitons in weakly perturbed integrable systems takes
place in the vicinity of the separatrix multi-soliton solutions of the
corresponding integrable equations, where even small perturbations can result
in a considerable change in the collision outcome. This conclusion is
illustrated through the use of the reduced three-particle model.Comment: 11 pages, 14 figures, submitted for publicatio
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