2,535 research outputs found
Magnetic Raman scattering of the ordered tetrahedral spin-1/2 clusters in Cu_2Te_2O_5(Br_(1-x)Cl_x)_2 compounds
Raman light-scattering experiments in the antiferromagnetic phase of the
Cu_2Te_2O_5(Br_(1-x)Cl_x)_2 compounds are analyzed in terms of a dimerized spin
model for the tetrahedral Cu-clusters. It is shown that the longitudinal
magnetic excitation in the pure Br system hybridizes with a localized singlet
excitation due to the presence of a Dzyaloshinskii-Moriya anisotropy term. The
drastic change of the magnetic scattering intensities observed when a
proportion of Br is replaced by Cl ions, is proposed to be caused by a change
of the magnetic order parameter. Instead of being parallel/antiparallel with
each other, the spins in the two pairs of spin-1/2 order perpendicular to each
other, when the composition x is larger than about 0.25.Comment: EPL, in pres
The Effect of Alliance Block Membership on Innovative Performance
Alliance, membership, Innovation, performance
Comment on: rotational properties of trapped bosons
Based on the Hellman-Feynman theorem it is shown that the average square
radius of a cloud of interacting bosons in a parabolic well can be derived from
their free energy. As an application, the temperature dependence of the moment
of inertia of non-interacting bosons in a parabolic trap is determined as a
function of the number of bosons. Well below the critical condensation
temperature, the Bose-Einstein statistics are found to substantially reduce the
moment of inertia of this system, as compared to a gas of ``distinguishable''
particles in a parabolic well.Comment: Herewith we repost our paper cond-mat/9611090 (1996). It was
published in Phys. Rev. A 55, 2453 (March 1997), three years before
cond-mat/0003471 (2000) by Schneider and Wallis. Reposted by
[email protected]
The center-of-mass response of confined systems
For confined systems of identical particles, either bosons or fermions, we
argue that the parabolic nature of the confinement potential is a prerequisite
for the non-dissipative character of the center of mass response to a uniform
probe. For an excitation in a parabolic confining potential, the half width of
the density response function depends nevertheless quantitatively on properties
of the internal degrees of freedom, as is illustrated here for an ideal
confined gas of identical particles with harmonic interparticle interactions.Comment: 4 pages REVTEX; accepted as Brief Communication in Phys. Rev.
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