7 research outputs found
Goldstone-Mode Phonon Dynamics in the Pyrochlore Cd2Re2O7
We have measured the polarized Raman scattering spectra of Cd2Re2O7, the
first superconducting pyrochlore, as a function of temperature. For
temperatures below the cubic-to-tetragonal structural phase transition (SPT) at
200K, a peak with B1 symmetry develops at zero frequency with divergent
intensity. We identify this peak as the first observation of the Goldstone
phonon in a crystalline solid. The Goldstone phonon is a collective excitation
that exists due to the breaking of the continuous symmetry with the SPT. Its
emergence coincides with that of a Raman-active soft mode. The order parameter
for both features derives from an unstable doubly-degenerate vibration (with Eu
symmetry) of the O1 atoms which drives the SPT.Comment: 4+ pages, 4 figures. Updated figures and text. Accepted to PR
Forces between cylindrical nanoparticles in a liquid crystal
Using classical density functional theory, the forces between two cylindrical nanoparticles in a liquid crystal solvent are calculated. Both the nematic and isotropic phases of the solvent are considered. In the nematic phase, the interaction is highly anisotropic. At short range, changes in the defect structure around the cylinders leads to a complex interaction between them. In the isotropic phase, an attractive interaction arises due to overlap between halos of ordered fluid adsorbed on the surfaces of the cylinders