Influence of the bias field on dielectric properties of the SmC_A* in the vicinity of the SmC*–SmC_A* phase transition

Abstract

In a large class of smectic mixtures prepared at our University, the phase transition between chiral ferroelectric smectic C (SmC*) and chiral antiferroelectric smectic C (SmCA*) phases can be observed on cooling. Under bias field the temperature of the phase transition SmC*−SmCA* decreases (ca. 100°C in the investigated mixture). The transition is called: unwound SmC*−twisted SmCA* phase transition. The Goldstone mode in SmC* phase is reduced by a direct current field while two modes (PH and PL) in the SmCA* phase are amplified. The amplitude of the fast X mode observed in the SmCA* phase is reduced. The aim of this paper is to show how parameters of the modes in SmCA* phase (calculated from Cole–Cole model) change with bias voltage—when twisted structure in SmCA* phase is gradually unwound. The character of the modes observed in SmCA* is discussed. A new effect is shown: a high value of dielectric loss is detected in the unwound SmC* phase, which is very close to SmCA*.