407 research outputs found
Neutrino scattering on polarized electron target as a test of neutrino magnetic moment
We suggest to use a polarized electron target for improving the sensitivity
of the search for the neutrino magnetic moment to the level in the processes of neutrino (antineutrino) -- electron
scattering. It is shown that in this case the weak interaction term in the
total cross section is significantly suppressed comparing with unpolarized
case, but the electromagnetic term does not depend on electron polarization.Comment: 11 pages, LaTeX2e, using elsart.cls and epsf.sty, 3 postscript
figures. Accepted in Phys. Lett.
Electrical resistivity, hall coefficient, and thermopower of optimally doped high-T c superconductors
© 2014, Pleiades Publishing, Inc. For a two-dimensional optimally doped antiferromagnet with spin S =1/2, we study the temperature dependence of the electrical resistivity ρ(T), Hall coefficient RH(T), and thermopower Q(T). The temperature dependence corresponding to optimally doped layered high-Tc superconducting cuprates has been obtained simultaneously for all three transport coefficients within the unified spin-polaron approach for the Kondo lattice. The key features of our study are the usage of the multimoment method for solving the kinetic equations (seven moments for the nonequilibrium distribution function ensure a good convergence) and the form of ac spin susceptibility χ(q, ω) for localized spins. For χ(q, ω), we choose a self-consistent expression which takes into account the “crossover” between the spin susceptibility determined by the self-consistent spherically symmetric Green’s function method and the semiphenomenological spin susceptibility corresponding to the critical decay of magnons
Dispersion of the dielectric function of a charge-transfer insulator
We study the problem of dielectric response in the strong coupling regime of
a charge transfer insulator. The frequency and wave number dependence of the
dielectric function and its inverse is the main object of consideration. We show that the
problem, in general, cannot be reduced to a calculation within the Hubbard
model, which takes into account only a restricted number of electronic states
near the Fermi energy. The contribution of the rest of the system to the
longitudinal response (i.e. to ) is essential
for the whole frequency range. With the use of the spectral representation of
the two-particle Green's function we show that the problem may be divided into
two parts: into the contributions of the weakly correlated and the Hubbard
subsystems. For the latter we propose an approach that starts from the
correlated paramagnetic ground state with strong antiferromagnetic
fluctuations. We obtain a set of coupled equations of motion for the
two-particle Green's function that may be solved by means of the projection
technique. The solution is expressed by a two particle basis that includes the
excitonic states with electron and hole separated at various distances. We
apply our method to the multiband Hubbard (Emery) model that describes layered
cuprates. We show that strongly dispersive branches exist in the excitonic
spectrum of the 'minimal' Emery model () and consider the
dependence of the spectrum on finite oxygen hopping and on-site
repulsion . The relationship of our calculations to electron energy loss
spectroscopy is discussed.Comment: 22 pages, 5 figure
Origin of spin-gap in CaVO: effect of frustration and lattice distortion
We study the origin of spin-gap in recently discovered material CaVO.
We analyze the spin- Heisenberg model on the depleted square lattice
with nearest neighbor (nn) and next nearest neighbor (nnn) interactions, in
terms of the singlet and triplet states of the 4-spin plaquettes and 2-spin
dimers. Phase diagram of the model is obtained within a linear
``spin-wave"-like approximation, and is shown to agree well with the earlier
results of QMC simulations for nn interactions. We further propose that the
special lattice structure of CaVO naturally leads to lattice
distortions, which enhances the spin-gap via a spin-Peierls mechanism.Comment: 4 pages, RevTex, 2 postscript figures. Latex file and figures have
been uuencode
Performances and stability of a 2.4 ton Gd organic liquid scintillator target for antineutrino detection
In this work we report the performances and the chemical and physical
properties of a (2 x 1.2) ton organic liquid scintillator target doped with Gd
up to ~0.1%, and the results of a 2 year long stability survey. In particular
we have monitored the amount of both Gd and primary fluor actually in solution,
the optical and fluorescent properties of the Gd-doped liquid scintillator
(GdLS) and its performances as a neutron detector, namely neutron capture
efficiency and average capture time. The experimental survey is ongoing, the
target being continuously monitored. After two years from the doping time the
performances of the Gd-doped liquid scintillator do not show any hint of
degradation and instability; this conclusion comes both from the laboratory
measurements and from the "in-tank" measurements. This is the largest stable
Gd-doped organic liquid scintillator target ever produced and continuously
operated for a long period
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