Lifshitz-Like Behaviour in Ferroelectric Liquid Crystals

In order to explain the anomalous behaviour of the critical magnetic field and the helical pitch in the vicinity of the Λ-line and the Lifshitz point in the ferroelectric liquid crystal DOBAMBC a model involving not only chiral but also non-chiral biquadratic coupling between the polarization and the tilt has been proposed. The model predicts an “S - like” dependence of the modulation wave vector close to the smectic C* - smectic A transition. High temperature resolution measurements of the helical pitch and the intensity of the diffraction sattelites indeed support the proposed model and seem to show that the pitch is finite at T_c. In such a case the Lifshitz field H_L is finite too.