Electric and magnetic-field-induced formation of macrostructures in ferroelectric liquid crystals

Background and Objectives: The study of ferroelectric liquid crystals in smectic C* phase fits together several most relevant research areas, including electro-optic devices with response time in the range of 10 $\mu$s. A distinguishing feature of smectic C* liquid crystals is its chiral layered structure, which is formed due to the center of masses orientational ordering along the preferred orientation [called the director]. The feasibility of creating thin liquid crystal films with different director's alignment at the substrates makes such films attractive for the study of confined volume effects. The nature of smectic C* molecules allowed to implement a series of electrooptical effects. Methods: Theoretical studies of this work include the functional approach. In particular, we introduced the functional of the free energy density in the desired form, then, its minimization can give the spatial distribution of the director field (or another quantity). Polarizing microscopy and fluorescent microscopy methods were used to observe the formation of macro-heterogeneities in the alignment of SmC* director field. Results: The simulation results reveal that a different alignment of long molecular axes (or director n) at the substrates leads to the soliton formations within the bulk of liquid crystal. The fluorescent confocal microscopy indicates the existence of such inhomogeneities within the bulk of the experimental cell. Another problem which we have discussed is related with the space dependence of the director field for any arbitrary layer structure and common parameters of smectic C*. It is also shown that only symmetric chevron structures exhibit the free energy minimum in the absence of electric field as well as when the electric field is applied. Conclusion: The fundamental effects associated with the different alignment of the director at the substrates, chevron defects and the director field dynamics in an external periodically oscillating magnetic field are discussed in this study.