Nonlinear dielectric response of antiferroelectric liquid crystals

We measure the nonlinear dielectric response of antiferroelectric liquid crystals in the SmC A*and SmC α*phase. In the SmC A*phase, the spectrum of the third-order nonlinear permittivity ε 3*shows a Debye-type relaxation and is ascribed to the deformation of helical structure due to the coupling between dielectric anisotropy and electric field. In the SmC α*phase, the spectrum of ε 3*shows a complicated form and is explained by the Landau-type phenomenological free-energy which is composed of the ferroelectric and the antiferroelectric order parameter.