Polarisation-dependent dielectric processes in ferroelectric liquid crystals

ABSTRACT

The behaviour of dielectric relaxation process has been investigated in four ferroelectric liquid crystal (FLC) materials having different spontaneous polarisation (Ps) values. Ps effect on the permittivity in four different FLCs has been carried out in highly anchored sample cells around ~8 μm thick. It has been found that the main contribution to the dielectric permittivity in chiral Smectic C (SmC*) phase is due to Goldstone mode (GM) and partially unwound helical mode (p-UHM). In higher PS value FLC materials, the p-UHM process is found to dominate the dielectric properties. It has also been observed that p-UHM process is highly dependent on the probing ac voltage and temperature, whereas GM is found to be weakly dependent of probing voltage and temperature in SmC* phase of all the studied FLC materials. The influential contribution of p-UHM has exhibited the dielectric properties in its intrinsic frequency range making the materials suitable for futuristic display and photonics devices.

Graphical Abstract

KEYWORDS:

• Ferroelectric liquid crystal
• dielectric
• spontaneous polarization
• phase transition

Acknowledgments

We sincerely thank the Director, National Physical Laboratory, New Delhi, for his continuous encouragement in this work. We would like to thank the Department of Science and Technology, New Delhi, India, for financial support through Project Grant GAP-150632 at NPL, New Delhi, India. We sincerely thank Dr A. V. Lapanik of Technical University Darmstadt, Germany, for synthesising deformed helix FLC (LAP-1) material. We sincerely thank Dr A. K. Thakur of Central University of Jammu, India, for useful discussion. A.M.B. and A.B. are thankful to Council of Scientific and Industrial Research (CSIR, India) for the financial assistance under an Emeritus Scheme.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

We would like to thank the Department of Science and Technology, New Delhi, India, for financial support through Project Grant GAP-150632 at NPL, New Delhi, India. A.M.B. and A.B. are thankful to Council of Scientific and Industrial Research (CSIR, India) for the financial assistance under an Emeritus Scheme.