703 research outputs found
Superconductivity and single crystal growth of Ni0:05TaS2
Superconductivity was discovered in a Ni0:05TaS2 single crystal. A Ni0:05TaS2
single crystal was successfully grown via the NaCl/KCl flux method. The
obtained lattice constant c of Ni0:05TaS2 is 1.1999 nm, which is significantly
smaller than that of 2H-TaS2 (1.208 nm). Electrical resistivity and
magnetization measurements reveal that the superconductivity transition
temperature of Ni0:05TaS2 is enhanced from 0.8 K (2H-TaS2) to 3.9 K. The
charge-density-wave transition of the matrix compound 2H-TaS2 is suppressed in
Ni0:05TaS2. The success of Ni0:05TaS2 single crystal growth via a NaCl/KCl flux
demonstrates that NaCl/KCl flux method will be a feasible method for single
crystal growth of the layered transition metal dichalcogenides.Comment: 13pages, 6 figures, Published in SS
Equivalence between non-bilinear spin- Ising model and Wajnflasz model
We propose the mapping of polynomial of degree 2S constructed as a linear
combination of powers of spin- (for simplicity, we called as spin-
polynomial) onto spin-crossover state. The spin- polynomial in general can
be projected onto non-symmetric degenerated spin up (high-spin) and spin down
(low-spin) momenta. The total number of mapping for each general spin- is
given by . As an application of this mapping, we consider a
general non-bilinear spin- Ising model which can be transformed onto
spin-crossover described by Wajnflasz model. Using a further transformation we
obtain the partition function of the effective spin-1/2 Ising model, making a
suitable mapping the non-symmetric contribution leads us to a spin-1/2 Ising
model with a fixed external magnetic field, which in general cannot be solved
exactly. However, for a particular case of non-bilinear spin- Ising model
could become equivalent to an exactly solvable Ising model. The transformed
Ising model exhibits a residual entropy, then it should be understood also as a
frustrated spin model, due to competing parameters coupling of the non-bilinear
spin- Ising model
Twist-3 Distribute Amplitude of the Pion in QCD Sum Rules
We apply the background field method to calculate the moments of the pion
two-particles twist-3 distribution amplitude (DA) in QCD sum
rules. In this paper,we do not use the equation of motion for the quarks inside
the pion since they are not on shell and introduce a new parameter to
be determined. We get the parameter in this approach. If
assuming the expansion of in the series in Gegenbauer polynomials
, one can obtain its approximate expression which can be
determined by its first few moments.Comment: 12 pages, 3 figure
Quasiparticle contribution to heat carriers relaxation time in DyBaCuO from heat diffusivity measurements
It is shown that the controversy on phonons or electrons being the most
influenced heat carriers below the critical temperature of high-T
superconductors can be resolved. Electrical and thermal properties of the same
DyBaCuO monodomain have been measured for two highly different
oxygenation levels. While the oxygenated sample DyBaCuO has very
good superconducting properties ( K), the DyBaCuO
sample exhibits an insulator behavior. A careful comparison between
measurements of the {\bf thermal diffusivity} of both samples allows us to
extract the electronic contribution. This contribution to the relaxation time
of heat carriers is shown to be large below and more sensitive to the
superconducting state than the phonon contribution.Comment: 13 pages, 6 figure
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High-temperature superconducting thin-film-based electronic devices
This the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project involved optimization of processing of Y123 and Tl-2212 thin films deposited on novel substrates for advanced electronic devices. The Y123 films are the basis for development of Josephson Junctions to be utilized in magnetic sensors. Microwave cavities based on the Tl-2212 films are the basis for subsequent applications as communication antennas and transmitters in satellites
Self-organized current transport through low angle grain boundaries in YBaCuO thin films, studied magnetometrically
The critical current density flowing across low angle grain boundaries in
YBaCuO thin films has been studied magnetometrically.
Films (200 nm thickness) were deposited on SrTiO bicrystal substrates
containing a single [001] tilt boundary, with angles of 2, 3, 5, and 7 degrees,
and the films were patterned into rings. Their magnetic moments were measured
in applied magnetic fields up to 30 kOe at temperatures of 5 - 95 K; current
densities of rings with or without grain boundaries were obtained from a
modified critical state model. For rings containing 5 and 7 degree boundaries,
the magnetic response depends strongly on the field history, which arises in
large part from self-field effects acting on the grain boundary.Comment: 8 pages, including 7 figure
GPDs of the nucleons and elastic scattering at high energies
Taking into account the electromagnetic and gravitational form factors,
calculated from a new set of -dependent GPDs, a new model is built. The
real part of the hadronic amplitude is determined only through complex . In
the framework of this model the quantitative description of all existing
experimental data at GeV, including the
Coulomb range and large momentum transfers ($0.0008 \leq |t| \leq 9.75 \
^237$ TeV is made.Comment: 14 pages, 21 figures, minor corrections (slightly brush English and
removed two misprint in numbering
A study of charged kappa in
Based on events collected by BESII, the decay
is studied. In the invariant mass
spectrum recoiling against the charged , the charged
particle is found as a low mass enhancement. If a Breit-Wigner function of
constant width is used to parameterize the kappa, its pole locates at MeV/. Also in this channel,
the decay is observed for the first time.
Its branching ratio is .Comment: 14 pages, 4 figure
Partial wave analysis of J/\psi \to \gamma \phi \phi
Using events collected in the BESII detector, the
radiative decay is
studied. The invariant mass distribution exhibits a near-threshold
enhancement that peaks around 2.24 GeV/.
A partial wave analysis shows that the structure is dominated by a
state () with a mass of
GeV/ and a width of GeV/. The
product branching fraction is: .Comment: 11 pages, 4 figures. corrected proof for journa
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