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Title: Electric-field-induced unwinding of ferroelectric helix in thin smectic C* layers with soft and rigid anchoring of molecules

Abstract

The unwinding of a helical structure in thin films of a ferroelectric smectic liquid crystal (LC) by an external electric field has been theoretically studied using a discrete model in which every LC layer is characterized by a two-dimensional vector {xi}{sub i} (describing the orientation of molecules) and by the polarization P{sub i}. It is established that the unwinding of the LC helix in thin films significantly differs from the well-known behavior of thick samples. In particular, discrete intermediate states (differing by an integer or half-integer number of turns) are formed in thin films for both weak and strong anchoring of molecules to a substrate surface. The physical factor responsible for this behavior is the presence of near-surface regions with thicknesses below the helix pitch and the corresponding uncompensated polarization.

Authors:
; ;  [1];  [2]
  1. Russian Academy of Sciences, Institute of Solid State Physics (Russian Federation)
  2. Laue-Langevin Institute (France)
Publication Date:
OSTI Identifier:
21241929
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Experimental and Theoretical Physics; Journal Volume: 107; Journal Issue: 3; Other Information: DOI: 10.1134/S1063776108090203; Copyright (c) 2008 Pleiades Publishing, Ltd; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ELECTRIC FIELDS; FERROELECTRIC MATERIALS; INTERMEDIATE STATE; LAYERS; LIQUID CRYSTALS; MOLECULES; ORIENTATION; POLARIZATION; SUBSTRATES; THIN FILMS; TWO-DIMENSIONAL CALCULATIONS

Citation Formats

Dolganov, P. V., Zhilin, V. M., E-mail: zhilin@issp.ac.ru, Dolganov, V. K., and Kats, E. I. Electric-field-induced unwinding of ferroelectric helix in thin smectic C* layers with soft and rigid anchoring of molecules. United States: N. p., 2008. Web. doi:10.1134/S1063776108090203.
Dolganov, P. V., Zhilin, V. M., E-mail: zhilin@issp.ac.ru, Dolganov, V. K., & Kats, E. I. Electric-field-induced unwinding of ferroelectric helix in thin smectic C* layers with soft and rigid anchoring of molecules. United States. doi:10.1134/S1063776108090203.
Dolganov, P. V., Zhilin, V. M., E-mail: zhilin@issp.ac.ru, Dolganov, V. K., and Kats, E. I. 2008. "Electric-field-induced unwinding of ferroelectric helix in thin smectic C* layers with soft and rigid anchoring of molecules". United States. doi:10.1134/S1063776108090203.
@article{osti_21241929,
title = {Electric-field-induced unwinding of ferroelectric helix in thin smectic C* layers with soft and rigid anchoring of molecules},
author = {Dolganov, P. V. and Zhilin, V. M., E-mail: zhilin@issp.ac.ru and Dolganov, V. K. and Kats, E. I.},
abstractNote = {The unwinding of a helical structure in thin films of a ferroelectric smectic liquid crystal (LC) by an external electric field has been theoretically studied using a discrete model in which every LC layer is characterized by a two-dimensional vector {xi}{sub i} (describing the orientation of molecules) and by the polarization P{sub i}. It is established that the unwinding of the LC helix in thin films significantly differs from the well-known behavior of thick samples. In particular, discrete intermediate states (differing by an integer or half-integer number of turns) are formed in thin films for both weak and strong anchoring of molecules to a substrate surface. The physical factor responsible for this behavior is the presence of near-surface regions with thicknesses below the helix pitch and the corresponding uncompensated polarization.},
doi = {10.1134/S1063776108090203},
journal = {Journal of Experimental and Theoretical Physics},
number = 3,
volume = 107,
place = {United States},
year = 2008,
month = 9
}
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  • Kondo [ital et] [ital al]. [Jpn. J. Appl. Phys. 22, L43 (1983)] discovered that both the smectic-[ital C] and smectic-[ital C][sup *] phases in the liquid crystal [ital p]-[ital n]-decyloxybenzylidene-[ital p]-amino-2-methylbutyl-cinnamate are reentrant with temperature for a range of electric fields. We show that the Landau theory with no adjustable parameters provides a semiquantitative explanation of the phase diagram. The double reentrance is due to two fourth-order terms, one chiral and the other achiral, and is intimately related to the maximum in the pitch, unlike the reentrance under magnetic field. The Sm-C--Sm-C[sup *] transition curve displays both main types ofmore » second-order phase transition, instability, and nucleation, separated by a first-order segment. [ital p]-azoxy-cinnamate-methyl-2-butanol and other compounds with divergent pitch should also show the double reentrance, but the physical origin is different.« less