Flexoelectricity and competition of time scales in electroconvection

Tóth-Katona, Tibor; Éber, Nándor; Buka, Ágnes; Krekhov, A. P.

doi:10.1103/physreve.78.036306

Cited by 26 publications

(18 citation statements)

References 49 publications

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“…The linear stability analysis of the extended SM provides the threshold U c (f ), the critical wave vector q c (f ) and the spatio-temporal dependence of the material flow v(r, t), the electric potential, and the director n(r, t) at the onset, in a good agreement with experiments [11]. The equations have solutions of three different types.…”

Section: Introductionsupporting

confidence: 61%

Suppression of spatially periodic patterns by dc voltage

et al. 2016

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The effect of superposed dc and ac applied voltages on two types of spatially periodic instabilities in nematic liquid crystals, flexoelectric domains (FD) and electroconvection (EC), was studied. The onset characteristics, threshold voltages and critical wave vectors, were determined. We found that in general the superposition of driving with different time symmetries inhibits the pattern forming mechanisms for FD and EC as well. As a consequence the onset extends to much higher voltages than the individual dc or ac thresholds. A dc bias induced reduction of the crossover frequency from the conductive to the dielectric EC regimes and a peculiar transition between two types of flexodomains with different wavelengths were detected. Direct measurements of the change of the electrical conductivity and its anisotropy, induced by the applied dc voltage component, showed that the dc bias substantially affects both parameters. Taking into account the experimentally detected variations of the conductivity in the linear stability analysis of the underlying nemato-hydrodynamic equations, a qualitative agreement with the experimental findings on the onset behaviour of spatially periodic instabilities was obtained.

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Section: Introductionsupporting

confidence: 61%

Suppression of spatially periodic patterns by dc voltage

et al. 2016

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“…Nonstandard electroconvection has been explained in the model taking into account flexopo larization [14,15] and ensuring good quantitative agreement with experimental threshold parameters. The considerable effect of flexopolarization on elec troconvection was also demonstrated earlier for NLCs with σ a > 0 [16,17].…”

Section: Introductionmentioning

confidence: 66%

On the role of flexoeffect in synchronization of electroconvective roll oscillations in nematics

Batyrshin

Krekhov

Scaldin

et al. 2012

J. Exp. Theor. Phys.

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We describe the dynamics of zigzag oscillations in a system of convective rolls in a nematic liquid crystal above the electroconvection threshold under the action of an ac voltage with a biased position of the mean value. It is found that an increase in the contribution from the constant component leads to a substantial increase in the spatiotemporal ordering of zigzag rolls and their synchronization with the homogeneous twist mode. The results confirm the flexoelectric mechanism of locking.

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“…Instead of systematic studies of parameter variations, which would go beyond the scope of this paper, we will restrict ourselves to selected nematics, which have not shown electroconvection under an applied dc voltage and where the material parameters are known to some extent. In detail we analyze thus experiments in the nematic mixtures Phase 4 [18] and Phase 5 [19,20], the rodlike compound 4-n-octyloxyphenyl 4-n-methyloxybenzoate (1OO8) [21], and a bent-core nematic 2,5-di4-[(4-heptylphenyl)difluoromethoxy]-phenyl-1,3,4-oxadiazole (7P-CF 2 OODBP) [14].…”

Section: Flexodomains In Real Nematics: Experiments and Theorymentioning

confidence: 99%

“…In Table I one [18], for the mixture Phase 5 from Ref. [19], and for the rodlike compound 4-n-octyloxyphenyl 4-n-methyloxybenzoate (1OO8) from Ref. [21].…”

Section: Appendix F: Experimental and Theoretical Data And Materials Pmentioning

confidence: 99%

Nonlinear analysis of flexodomains in nematic liquid crystals

et al. 2018

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We investigate flexodomains, which are observed in planar layers of certain nematic liquid crystals, when a dc voltage U above a critical value U c is applied across the layer. They are characterized by stationary stripelike spatial variations of the director in the layer plane with a wave number p(U). Our experiments for different nematics demonstrate that p(U) varies almost linearly with U for U > U c. That is confirmed by a numerical analysis of the full nonlinear equations for the director field and the induced electric potential. Beyond this numerical study, we demonstrate that the linearity of p(U) follows even analytically, when considering a special parameter set first used by Terent'ev and Pikin [Sov. Phys. JETP 56, 587 (1982)]. Their theoretical paper serves until now as the standard reference on the nonlinear analysis of flexodomains, since it has arrived at a linear variation of p(U) for large U U c. Unfortunately, the corresponding analysis suffers from mistakes, which in a combination led to that result.

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Flexoelectricity and competition of time scales in electroconvection

Cited by 26 publications

References 49 publications

Suppression of spatially periodic patterns by dc voltage

Suppression of spatially periodic patterns by dc voltage

On the role of flexoeffect in synchronization of electroconvective roll oscillations in nematics

Nonlinear analysis of flexodomains in nematic liquid crystals

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