Collective dielectric processes at the transition temperature of the Sm−C* and Sm−A* phase in a ferroelectric liquid crystal

Abstract

An anomalous dielectric relaxation process, called the partially unwound helical mode (p-UHM), is a collective dielectric process apart from the well known Goldstone and soft mode process; it is studied in the smectic C^{*} (Sm-C^{*}) phase and at the transition temperature of the Sm-C^{*}-Sm-A^{*} phase in the ferroelectric liquid crystal (FLC) material. To avoid the surface effect, a thick cell of 40 μm thickness was prepared with highly rubbed surfaces of the ITO substrates. It has been observed that the dielectric properties in Sm-C^{*} and at the T_{c} temperature are dominated by the p-UHM process which is dependent on an applied oscillating field in the Sm-C^{*} phase. The probing ac and dc bias field dependences of all these collective dielectric processes have been reported in the Sm-C^{*} and Sm-A^{*} phases of FLC materials.

Alignment layer and helix controlled unconventional operational switching in ferroelectric liquid crystal

“…The new relaxation process, caused by the interface of FLC and strongly anchored alignment layer interaction, is always found at lower frequency than the phase fluctuation i.e. GM process and is found dependent on various other parameters like probing AC voltage [14], DC bias voltage, temperature [15,16], spontaneous polarization (P s ) [17]. On the other hand, if the rubbing strength is kept weak, the new relaxation mode is observed in surface stabilized cells [6].…”

Ultra‐Broadband Tunable Bragg–Berry Optical Vortex Generators of a Circularly Symmetric Chiroptic Structure

“…FLC materials have unique electro‐optical and dielectric features, such as spontaneous polarization, fast response time, high contrast ratio, and molecular dynamics. [ 32–34 ] FLC‐doped CLC (FLC‐CLC) with a SmC*‐CLC transition point slightly below room temperature is used in this study to fabricate BBOVGs with a circularly symmetric planar texture. The devices can be electrically tuned in a low‐voltage range (≤3.0 V) at near room temperature such that the PBG can continuously shift throughout almost the entire visible region (approximately 400–700 nm) due to the high sensitivity of the pitch of the CLC near the SmC*–CLC transition point on the temperature.…”