2,326 research outputs found
Experimentally observed evolution between dynamic patterns and intrinsic localized modes in a driven nonlinear electrical cyclic lattice
Locked intrinsic localized modes (ILMs) and large amplitude lattice spatial
modes (LSMs) have been experimentally measured for a driven 1-D nonlinear
cyclic electric transmission line, where the nonlinear element is a saturable
capacitor. Depending on the number of cells and electrical lattice damping a
LSM of fixed shape can be tuned across the modal spectrum. Interestingly, by
tuning the driver frequency away from this spectrum an LSM can be continuously
converted into ILMs and visa versa. The differences in pattern formation
between simulations and experimental findings are due to a low concentration of
impurities. Through this novel nonlinear excitation and switching channel in
cyclic lattices either energy balanced or unbalanced LSMs and ILMs may occur.
Because of the general nature of these dynamical results for nonintegrable
lattices applications are to be expected. The ultimate stability of driven aero
machinery containing nonlinear periodic structures may be one example.Comment: 7 pages 7 figure
Comparative study of the effects of electron irradiation and natural disorder in single crystals of SrFe(AsP) (0.35) superconductor
London penetration depth, , was measured in single crystals of
SrFe(AsP) (0.35) iron - based superconductor. The
influence of disorder on the transition temperature, , and on
was investigated. The effects of scattering controlled by the annealing of
as-grown crystals was compared with the effects of artificial disorder
introduced by 2.5~MeV electron irradiation. The low temperature behavior of
can be described by a power-law function, , with the exponent close to one in pristine annealed samples, as
expected for superconducting gap with line nodes. Upon
\ecm irradiation, the exponent increases rapidly exceeding a dirty limit
value of 2 implying that the nodes in the superconducting gap are
accidental and can be lifted by the disorder. The variation of the exponent
with is much stronger in the irradiated crystals compared to the crystals
in which disorder was controlled by the annealing of the growth defects. We
discuss the results in terms of different influence of different types of
disorder on intra- and inter- band scattering
Glauber dynamics in a single-chain magnet: From theory to real systems
The Glauber dynamics is studied in a single-chain magnet. As predicted, a
single relaxation mode of the magnetization is found. Above 2.7 K, the
thermally activated relaxation time is mainly governed by the effect of
magnetic correlations and the energy barrier experienced by each magnetic unit.
This result is in perfect agreement with independent thermodynamical
measurements. Below 2.7 K, a crossover towards a relaxation regime is observed
that is interpreted as the manifestation of finite-size effects. The
temperature dependences of the relaxation time and of the magnetic
susceptibility reveal the importance of the boundary conditions.Comment: Submitted to PRL 10 May 2003. Submitted to PRB 12 December 2003;
published 15 April 200
Universal observation of multiple order parameters in cuprate superconductors
The temperature dependence of the London penetration depth \lambda was
measured for an untwined single crystal of YBa_2Cu_3O_{7-\delta} along the
three principal crystallographic directions (a, b, and c). Both in-plane
components (\lambda_a and \lambda_b) show an inflection point in their
temperature dependence which is absent in the component along the c-direction
(\lambda_c). The data provide convincing evidence that the in-plane
superconducting order parameter is a mixture of s+d-wave symmetry whereas it is
exclusively s-wave along the c-direction. In conjunction with previous results
it is concluded that coupled s+d-order parameters are universal and intrinsic
to cuprate superconductors.Comment: 5 pages, 3 figure
Observational Artifacts of NuSTAR: Ghost Rays and Stray Light
The Nuclear Spectroscopic Telescope Array (NuSTAR), launched in June 2012,
flies two conical approximation Wolter-I mirrors at the end of a 10.15m mast.
The optics are coated with multilayers of Pt/C and W/Si that operate from 3--80
keV. Since the optical path is not shrouded, aperture stops are used to limit
the field of view from background and sources outside the field of view.
However, there is still a sliver of sky (~1.0--4.0 degrees) where photons may
bypass the optics altogether and fall directly on the detector array. We term
these photons Stray-light. Additionally, there are also photons that do not
undergo the focused double reflections in the optics and we term these Ghost
Rays. We present detailed analysis and characterization of these two components
and discuss how they impact observations. Finally, we discuss how they could
have been prevented and should be in future observatories.Comment: Published in Journal of Astronomical Telescopes, Instruments, and
Systems. Open Access. http://dx.doi.org/10.1117/1.JATIS.3.4.04400
Effect of cation size variance on spin and orbital order in Eu(LaY)VO
We have investigated the -ion ( = rare earth or Y) size variance effect
on spin/orbital order in Eu(LaY)VO. The
size variance disturbs one-dimensional orbital correlation in -type
spin/-type orbital ordered states and suppresses this spin/orbital order. In
contrast, it stabilizes the other spin/orbital order. The results of neutron
and resonant X-ray scattering denote that in the other ordered phase, the
spin/orbital patterns are -type/-type, respectively.Comment: 4 pages, 4 figures, accepted to Rapid Communication in Physical
Review
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