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Hydration-induced anisotropic spin fluctuations in Na_{x}CoO_{2}\cdot1.3H_{2}O superconductor
We report ^{59}Co NMR studies in single crystals of cobalt oxide
superconductor Na_{0.42}CoO_{2}\cdot1.3H_{2}O (T_c=4.25K) and its parent
compound Na_{0.42}CoO_{2}. We find that both the magnitude and the temperature
(T) dependence of the Knight shifts are identical in the two compounds above
T_c. The spin-lattice relaxation rate (1/T_1) is also identical above T_0
\sim60 K for both compounds. Below T_0, the unhydrated sample is found to be a
non-correlated metal that well conforms to Fermi liquid theory, while spin
fluctuations develop in the superconductor. These results indicate that water
intercalation does not change the density of states but its primary role is to
bring about spin fluctuations. Our result shows that, in the hydrated
superconducting compound, the in-plane spin fluctuation around finite wave
vector is much stronger than that along the c-axis, which indicates that the
spin correlation is quasi-two-dimensional.Comment: 4 pages, 5 figure
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The nuclear equation of state probed by production in heavy ion collisions
The dependence of production on the nuclear equation of state is
investigated in heavy ion collisions. An increase of the excitation function of
multiplicities obtained in heavy () over light () systems
when going far below threshold which has been observed by the KaoS
Collaboration strongly favours a soft equation of state. This observation holds
despite of the influence of an in-medium kaon potential predicted by effective
chiral models which is necessary to reproduce the experimental yields.
Phase space effects are discussed with respect to the excitation
function.Comment: 14 pages Revtex, 6 figures, Proceedings to the XXXIX Interantional
Winter Meeting on Nuclear Physics, Bormio, Italy, 200
A real-space grid implementation of the Projector Augmented Wave method
A grid-based real-space implementation of the Projector Augmented Wave (PAW)
method of P. E. Blochl [Phys. Rev. B 50, 17953 (1994)] for Density Functional
Theory (DFT) calculations is presented. The use of uniform 3D real-space grids
for representing wave functions, densities and potentials allows for flexible
boundary conditions, efficient multigrid algorithms for solving Poisson and
Kohn-Sham equations, and efficient parallelization using simple real-space
domain-decomposition. We use the PAW method to perform all-electron
calculations in the frozen core approximation, with smooth valence wave
functions that can be represented on relatively coarse grids. We demonstrate
the accuracy of the method by calculating the atomization energies of twenty
small molecules, and the bulk modulus and lattice constants of bulk aluminum.
We show that the approach in terms of computational efficiency is comparable to
standard plane-wave methods, but the memory requirements are higher.Comment: 13 pages, 3 figures, accepted for publication in Physical Review
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