LOW-FREQUENCY RELAXATIONS IN A FERROELECTRIC LIQUID-CRYSTAL WITH THE HELIX TWIST INVERSION

Dielectric dispersion has been studied in the frequency range of 10Hz divided by 1MHz in a liquid crystal with 2-alkoxypropionate chiral gro up, which exhibits the helix twist inversion in the SmC phase at abou t 109 degrees C. The dispersion reveals two modes, dielectric strength s as well as relaxation frequencies of which exhibit a strong dependen ce on the sample thickness. Both modes are also detected in the electr ooptic response. The mode with the relaxation in the kHz range is the Goldstone mode, which is combined with the thickness mode. In the temp erature range near the inversion temperature, where the helicoidal str ucture is unwound, it becomes the pure thickness mode. The origin of t he lower frequency mode, which is detected for the first time, remains unexplained.