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.