Soft Mode Behavior Near the Critical Endpoint of a Nematic Liquid Crystal with Positive Dielectric Anisotropy

Abstract

A critical endpoint appears when a DC electric field is applied to a nematic liquid crystal with positive dielectric anisotropy. We have investigated the soft mode behavior near the critical endpoint of the nematic liquid crystal 8CB by dielectric spectroscopy while finely varying the temperature and DC electric field around it. Using an expression for the dielectric constant derived from the Landau–de Gennes theory, we obtained the relaxation strength and frequency for the soft mode from dielectric dispersions. An increase in relaxation strength and a decrease in relaxation frequency were observed as the critical endpoint was approached, which was expected from the theory.