760 research outputs found
Hybridization and interference effects for localized superconducting states in strong magnetic field
Within the Ginzburg-Landau model we study the critical field and temperature
enhancement for crossing superconducting channels formed either along the
sample edges or domain walls in thin-film magnetically coupled superconducting
- ferromagnetic bilayers. The corresponding Cooper pair wave function can be
viewed as a hybridization of two order parameter (OP) modes propagating along
the boundaries and/or domain walls. Different momenta of hybridized OP modes
result in the formation of vortex chains outgoing from the crossing point of
these channels. Near this crossing point the wave functions of the modes merge
giving rise to the increase in the critical temperature for a localized
superconducting state. The origin of this critical temperature enhancement
caused by the wave function squeezing is illustrated for a limiting case of
approaching parallel boundaries and/or domain walls. Using both the variational
method and numerical simulations we have studied the critical temperature
dependence and OP structure vs the applied magnetic field and the angle between
the crossing channels.Comment: 12 pages, 13 figure
Infrared and THz studies of polar phonons and improper magnetodielectric effect in multiferroic BFO3 ceramics
BFO3 ceramics were investigated by means of infrared reflectivity and time
domain THz transmission spectroscopy at temperatures 20 - 950 K, and the
magnetodielectric effect was studied at 10 - 300 K, with the magnetic field up
to 9 T. Below 175 K, the sum of polar phonon contributions into the
permittivity corresponds to the value of measured permittivity below 1 MHz. At
higher temperatures, a giant low-frequency permittivity was observed, obviously
due to the enhanced conductivity and possible Maxwell-Wagner contribution.
Above 200 K the observed magnetodielectric effect is caused essentially through
the combination of magnetoresistance and the Maxwell-Wagner effect, as recently
predicted by Catalan (Appl. Phys. Lett. 88, 102902 (2006)). Since the
magnetodielectric effect does not occur due to a coupling of polarization and
magnetization as expected in magnetoferroelectrics, we call it improper
magnetodielectric effect. Below 175 K the magnetodielectric effect is by
several orders of magnitude lower due to the decreased conductivity. Several
phonons exhibit gradual softening with increasing temperature, which explains
the previously observed high-frequency permittivity increase on heating. The
observed non-complete phonon softening seems to be the consequence of the
first-order nature of the ferroelectric transition.Comment: subm. to PRB. revised version according to referees' report
Nanostructured materials for optoelectronic applications
Study and optimization of new nanoscale materials useful for optoelectronic application have been considered. The search for the effective nanostructured materials has been revealed in two directions: to optimize the mechanical hardness of the inorganic systems and to increase the photorefractive parameters of the organics with nanoobjects. It has been testified that the surface mechanical properties of the inorganic materials via nanotubes treatment process can be drastically improved. For example, the surface mechanical hardness of the UV and IR range soft materials can be increased up to 3-10 times under the conditions of oriented nanotubes placement. It has been obtained that the nonlinear optical characteristics (nonlinear refraction n2 and cubic nonlinearity x(3)) of the organics thin films sensitized with fullerenes or nanotubes can be increased up to 3-4 orders of magnitude in comparison with the same parameters for bulk materials traditionally used for nonlinear optics.Selected papers presented at the Eleventh Annual Conference of the Materials Research Society of Serbia, YUCOMAT 200
The lightest scalar glueball
Recently performed investigations of meson spectra allow us to determine the
resonance structure for the waves , , ,
= in the mass region up to 1900 MeV, thus
establishing the meson multiplets and .
Experimental data demonstrate that there are five scalar/isoscalar states in
this mass region. Four of them are states, that is, members of the
and nonets, while the fifth state is an extra
one not accomodated by systematics; it has the properties of the
lightest scalar glueball. Analysis of the -wave performed within the
framework of the dispersion relation technique allows us to reconstruct the
mixing of a pure gluonium with neighbouring scalar states belonging
to and nonets: three scalar mesons share the
gluonium state between each other -- those are two comparatively narrow
resonances and and a broad resonance
. The broad state is a descendant of the gluonium,
keeping about 40-50% of its component.Comment: 48 pages, LaTeX, 25 PostScript figures, epsfig.sty. Submitted to
Russian Journal Uspekhi Fiz. Nauk (Phys-Uspekhi
Measurement of decay rate and parameters at KEDR
Using the inclusive photon spectrum based on a data sample collected at the
peak with the KEDR detector at the VEPP-4M collider, we
measured the rate of the radiative decay as well
as mass and width. Taking into account an asymmetric photon
lineshape we obtained keV, MeV/, MeV.Comment: 6 pages, 3 figure
Measurement of B(J/psi->eta_c gamma) at KEDR
We present a study of the inclusive photon spectrum from 6.3 million J/psi
decays collected with the KEDR detector at the VEPP-4M e+e- collider. We
measure the branching fraction of the radiative decay J/psi -> eta_c gamma,
eta_c width and mass. Taking into account an asymmetric photon line shape we
obtain: M(eta_c) = (2978.1 +- 1.4 +- 2.0) MeV/c^2, Gamma(eta_c) = (43.5 +- 5.4
+- 15.8) MeV, B(J/psi->eta_c gamma) = (2.59 +- 0.16 +- 0.31)%$.Comment: 6 pages, 1 figure. To be published in the proceedings of the 4th
International Workshop on Charm Physics (Charm2010), October 21-24, 2010,
IHEP, Beijin
Measurement of J/psi to eta_c gamma at KEDR
We present a study of the inclusive photon spectra from 5.9 million J/psi
decays collected with the KEDR detector at the VEPP-4M e+e- collider. We
measure the branching fraction of radiative decay J/psi to eta_c gamma, eta_c
width and mass. Our preliminary results are: M(eta_c) = 2979.4+-1.5+-1.9 MeV,
G(eta_c) = 27.8+-5.1+-3.3 MeV, B(J/psi to eta_c gamma) = (2.34+-0.15+-0.40)%.Comment: To be published in Proceedings of the PhiPsi09, Oct. 13-16, 2009,
Beijing, Chin
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