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Low-frequency dielectric processes in deformed helix ferroelectric liquid crystals

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Abstract

A low-frequency dielectric relaxation mode in deformed helix ferroelectric liquid crystal (DHFLC) has been observed at the interface of strongly rubbed substrates and DHFLC material which may find applications in low power consumption FLC devices. The surface-induced dielectric relaxation process at the interface of DHFLC and substrate is called the partially unwound helical mode (p-UHM) due to the unwinding of the helical structure at this interface. After investigation of the material under various parameters such as temperature, variation of the amplitude of probing ac voltage and dc bias voltage, the relaxation frequency of p-UHM is found to be shifted towards Goldstone mode and merged with it. The relaxation frequency of Goldstone mode is found to decrease, whereas the relaxation frequency of p-UHM process increases with the increase in temperature of DHFLC. Finally, both the modes merge and the resultant relaxation frequency is found to be lower than Goldstone mode in SmC* phase. It seems that phason mode and partial helical unwinding mode are coupled together due to dipole moment that is resulting in a new relaxation frequency. p-UHM process is significant for low-power displays and non-displays applications like a part of sensor where weak electric signal is required to be realized without pre-amplification.

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Acknowledgements

We sincerely thank the Director, Dr. D. K. Aswal, 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 Science and Engineering Research Board Grant GAP-150632 at NPL, New Delhi, India. We (A.M.B. and A.B.) are thankful to Council of Scientific and Industrial Research (CSIR, India) (21/(0986)/13-EMR-II) for the financial assistance under an Emeritus Scheme.

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Correspondence to Amit Choudhary or Ashok M. Biradar.

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Bawa, A., Choudhary, A., Thakur, A.K. et al. Low-frequency dielectric processes in deformed helix ferroelectric liquid crystals. Appl. Phys. A 126, 171 (2020). https://doi.org/10.1007/s00339-020-3340-z

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Keywords

  • Deformed helix ferroelectric liquid crystal
  • Dielectric spectroscopy
  • Surface interface