Nonlinear dielectric relaxation spectroscopy of ferroelectric liquid crystals in the smectic C^* phase

We have applied a nonlinear dielectric relaxation spectroscopy to the Goldstone mode of ferroelectric liquid crystals (FLCs) in the chiral smectic C phase. The linear spectrum shows a single relaxation of Debye type. The third and fifth-order nonlinear spectra show extended forms of Debye type to the nonlinear cases. We have also calculated the nonlinear dielectric spectra theoretically by means of the torque balance equation describing the dynamics of FLCs. The theoretical spectra in which we have taken into the distribution of the relaxation times make good agreement with the measured ones. We also discuss the application of nonlinear dielectric relaxation spectroscopy to the simultaneous measurement of material constants of FLCs.