抄録
Nonlinear dielectric response has been studied in various kinds of smectic-C like sub-phases in antiferroelectric liquid crystals. These sub-phases are also clearly distinguished in temperature dispersion of nonlinear permittivity. We have succeeded to detect some fluctuation modes those are not observed in linear dielectric spectrum by third-order nonlinear spectrum. One is the soft mode of SmC_α^* phase and that appears remarkably in the vicinity of SmA-SmC_α^* phase transition. The other is the antiferroelectric Goldstone mode with low relaxation frequency and is observed in both AF and SmC_A^* phases. These findings show the usefulness of nonlinear dielectric spectroscopy in research of these liquid crystals.
