Hysteresis-free electro-optical switching in conductive ferroelectric liquid crystals: experiments and modelling

Abstract

The hysteresis-free electro-optical switching, or so-called V-shaped, regime has been studied in a commercial ferroelectric liquid crystal (FLC) mixture having a smectic C* phase with a very small value of spontaneous polarization. The FLC was introduced into commercial EHC cells with thin aligning layers. In such cells V-shaped switching could be observed only at very low frequencies, less than 1 Hz. However, when the same material is strongly doped with a conductive impurity, its conductivity markedly increases and hysteresis-free switching is observed over a wide range of applied frequencies and voltages. Experimental results are in good agreement with computer modelling carried out as part of this work. The modelling takes into account all the important parameters of smectic C* FLC: non-polar anchoring conditions, possible bookshelf and chevron structures, the capacitance of the aligning layers and the conductivity of a FLC. The last two factors appear to be the most crucial for hysteresis-free switching in the smectic C* phase.