The effect of the sample thickness on the collective modes in ferroelectric liquid crystals

Abstract

Complex permittivity ε* has been studied in the vicinity of the SmA-SmC* phase transition for samples 6, 12, 25, 50, and 100 μm thick. In the studied frequency range of (10¹−10⁶) Hz the relaxation of collective modes, namely the soft, Goldstone and/or “thickness” modes, occurs. From the frequency dependence of ε* the relaxation frequency, f_r , and dielectric strength, Δε, of these modes are determined in dependence of temperature and the sample thickness. Results are discussed on the basis of a phenomenological theory taking into account surface interactions.

Keywords:

• ferroelectric liquid crystals
• dielectric relaxation
• softmode
• Goldstone-mode
• cell thickness dependence