Unipolar “V-shaped” switching in chiral smectic C (Sm–C[sup ∗]) liquid crystals bounded by an ion-store film (original) (raw)

Ferroelectric switching and phase transitions in thin cells of chiral smectic liquid crystals

Surface Science, 2004

Ferroelectric smectic C Ã (SmC Ã )-smectic A Ã (SmA Ã ) phase transitions and ferroelectric switching in thin planar cells of chiral liquid crystals (LC) are studied by second harmonic generation (SHG) technique. Electric field and temperature dependences of reflected and transmitted SHG are studied in order to distinguish between non-linear optical response from the sub-surface layer and the bulk of the LC cell. The analysis of the SHG temperature dependences shows a strong surface coupling resulting in the existence of an unswitchable ''frozen'' sub-surface layer which retains a stable structure under the application of a DC electric field and temperature variations. Critical exponents in the vicinity of the ferroelectric phase transition show a behavior corresponding to the superfluid helium theory.

V-shaped electro-optic response observed in a chiral ferroelectric smectic liquid crystal

Applied Physics Letters, 2008

We report on the observation of V-shaped switching in a ferroelectric liquid crystal cell over a wide range of temperatures. Results of the optical transmittance in the visible region give us the helical pitch for various temperatures of the ferroelectric liquid crystalline compound used. We show that the helical pitch, in addition to the spontaneous polarization ͑P S ͒ and thickness of the alignment layer of the cell, is an important factor in giving V-shaped switching. A longer or helical compensated mixture gives a better V-shaped switching.

Switching behaviour and electro-optic response due to the soft mode ferroelectric effect in chiral smectic A liquid crystals

Liquid Crystals, 1991

The switching characteristics and the electro-optic response due to the electroclinic effect in chiral smectic A liquid crystals are analysed theoretically. We give an exact analytic solution to the dynamic equation of the tilt angle (8) up to the O4 term in the Landau expansion of the free energy. The non-linear behaviour of B and the characteristic. time under an applied electric field are described near the S2-S; transition. They both have a finite value at the transition which depends on the field. The characteristic time (to) exhibits a critical slowing down at sufficiently low fields, which occurs only in the early stages of the switching. At late stages, the switching time exhibits a maximum at a particular temperature which depends on the field, and then decreases in a very narrow temperature range near the transition. The U4 term is important in explainingcertain properties even for very small 6, and it becomes essential for B > 5". The optical response of an electroclinic liquid crystal cell is considered in detail. We derive an expression for the output intensity of light passing through an electroclinic cell. The delay and rise times for the optical signal are shown to a first approximation to be 0.379 to and 2.577 to, respectively.

Ferroelectric ordering and electroclinic effect in chiral smectic liquid crystals

Physical Review E, 2004

Ferroelectric ordering, the electroclinic effect and chiral smectic C (SmC*) -smectic A (SmA*) phase transitions in thin planar ferroelectric liquid crystal (FLC) cells are studied by means of linear electrooptic and second harmonic generation techniques. The ferroelectric switching is detected in biased FLC cells by measuring azimuthal dependences of linear and nonlinear responses. The applied DC-electric field rotates the FLC symmetry axis with initial and final orientations in the cell plane. Comparative studies of the switching behavior in reflection and transmission allows to distinguish the contributions from the bulk and the sub-surface layers of the cell. The analysis of temperature dependence shows the existence of a strong surface coupling. The temperature dependent nonlinear polarization shows a critical behavior corresponding to the superfluid model.

Analysis of Nonlocal Electrostatic Effects in Chiral Smectic C Liquid Crystals

Siam Journal on Applied Mathematics, 2006

We present modeling and analysis of smectic C phases of liquid crystals capable of sustaining spontaneous polarization. The layered liquid crystals are also assumed to be chiral. We study minimization of the total energy subject to electrostatic constraints. In order to determine mathematically and physically relevant boundary conditions, we appeal to the analogy between the current problem and the vorticity in fluids. We place a special emphasis on the nonlocal and selfenergy effects arising from spontaneous polarization. We discuss examples pertaining to the electric field created by the liquid crystal in dielectric media, and also to the possible role of a domain shape as an energy reduction mechanism.

Electric field induced phase transition in a ferroelectric smectic-C* liquid crystal

The European Physical Journal Applied Physics, 2011

We have experimentally investigated the unwinding process of the ferroelectric Sm-C * phase of a chiral AFLC smectic liquid crystal compound 12OF1M7 using the electro-optic properties, microscopic observations and constant current method. We found that this process occurs via two steps through an intermediate phase. Furthermore, we have established the (E-T) phase diagram of the studied compound by combining the experimental results.

Modeling and simulation of switchings in ferroelectric liquid crystals

Discrete and Continuous Dynamical Systems, 2009

Mathematical modeling and numerical simulation of smectic C liquid crystals which possess the spontaneous polarization are considered in this paper. In particular, the model allows for a system with a zero net polarization which is one of the ubiquitous systems of the polarized liquid crystals. Theoretical and numerical investigations are conducted to study effects of the energy associated with the polarization, switching patterns between two uniform states by an externally applied field and random noise, as well as a relation between polarization and applied field near the phase transition from the smectic A and smectic C.

New electromechanical effect in chiral smectic C* liquid crystals

1985

Re~u le 29 mars 1985, revise le 22 mai, accepte le 17 juin 1985) Résumé. 2014 Un nouvel effet électromécanique a été trouvé dans des cristaux liquides S*C orientés planairement, sous l'influence d'un champ électrique alternatif appliqué. En plus du phénomène électrooptique bien connu, des vibrations mécaniques ont été observées dans la direction parallèle aux couches smectiques et perpendiculaire au champ électrique. Abstract. 2014 A new electromechanical effect has been found in planar oriented S*C liquid crystals under the influence of an applied alternating electric field. Apart from the well-known electrooptical effects a mechanical vibration has been observed in a direction parallel to the smectic layers and perpendicular to the electric field. J. Physique Lett. 46 (1985) L-759 -L-761 15 AOÛT 1985, Classification