NONLINEAR DIELECTRIC-SPECTROSCOPY OF THE GOLDSTONE MODE IN AN ANTIFERROELECTRIC LIQUID-CRYSTAL

The third-order nonlinear dielectric constant of an antiferroelectric liquid crystal, MHPOBC, was measured in the antiferroelectric phase (SmCA*). The third-order dielectric relaxation due to the antiferroelectric Goldstone mode was observed, which was Debye-type. This Debye-type relaxation in the third-order dielectric response indicates that the third-order dielectric constant should be proportional to the linear susceptibility of the antiferroelectric Goldstone mode. The temperature dependence of the relaxation frequency was obtained from the third-order dielectric constant. By comparing it with that obtained by the photon correlation spectroscopy, it was found that the surface anchoring has a great influence on the helical pitch.