No abstract

We analyzed the complex dielectric and Raman spectra of hydrogen-bond liquids in the microwave to terahertz frequency range. As for water and methanol, the high-frequency component of the dielectric spectrum, i.e., the small deviation from the principal Debye relaxation, clearly corresponds to the Raman spectrum. This indicates that the cooperative relaxation, accompanied by huge polarization fluctuation, is virtually not Raman active, whereas the faster processes reflect common microscopic dynamics. For ethylene glycol, the shape of the Raman spectrum also resembles that of the high-frequency deviation of the dielectric spectrum, but, additionally, a weak manifestation of the cooperative relaxation arising from quadrupolar conformers is detected.

Any polar-ordered material with a spatially uniform polarization field is internally frustrated: The symmetry-required local preference for polarization is to be nonuniform, i.e., to be locally bouquet-like or "splayed." However, it is impossible to achieve splay of a preferred sign everywhere in space unless appropriate defects are introduced into the field. Typically, in materials like ferroelectric crystals or liquid crystals, such defects are not thermally stable, so that the local preference is globally frustrated and the polarization field remains uniform. Here, we report a class of fluid polar smectic liquid crystals in which local splay prevails in the form of periodic supermolecular-scale polarization modulation stripes coupled to layer undulation waves. The polar domains are locally chiral, and organized into patterns of alternating handedness and polarity. The fluid-layer undulations enable an extraordinary menagerie of filament and planar structures that identify such phases.