Dielectric study of the electroclinic effect in the smectic-A phase

The dielectric properties of a smectic-A liquid crystal in the presence of a dc bias field are studied in the frequency range 100 Hz–1 MHz. It is shown that near the smectic-A–smectic-${\mathit{C}}^{\mathrm{*}}$ phase transition the relaxation frequency and dielectric strength of the soft mode have nonlinear bias field dependencies resulting from an electroclinic coupling between the molecular tilt and the polarization. A simple mean field theory is proposed to explain the experimental results.