Static and dynamic properties of cholesteric fingers in electric field

Oswald, P.; Baudry, Jean; Pirkl, S.

doi:10.1016/s0370-1573(00)00056-9

Cited by 143 publications

(194 citation statements)

References 36 publications

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“…These variations can be induced by temperature or by an electric field. Previous and more recent works have analysed the problem using simple elastic models [17][18][19][20][21][22][23][24]. There are various experimental works that deal with these problems [25][26][27][28][29][30][31][32][33].…”

Section: Introductionmentioning

confidence: 99%

Capillary and winding transitions in a confined cholesteric liquid crystal

2015

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We consider a Lebwohl-Lasher model of chiral particles confined in a planar cell (slit pore) with different boundary conditions, and solve it using mean-field theory. The phase behaviour of the system with respect to temperature and pore width is studied. Two phenomena are observed: (i) an isotropic-cholesteric transition which exhibits an oscillatory structure with respect to pore width, and (ii) an infinite set of winding transitions caused by commensuration effects between cholesteric pitch and pore width. The latter transitions have been predicted and analysed by other authors for cholesterics confined in a fixed pore and subject to an external field promoting the uniaxial nematic phase; here we induce winding transitions solely from geometry by changing the pore width at zero external field (a setup recently explored in Atomic-Force Microscopy experiments). In contrast with previous studies, we obtain the phase diagram in the temperature vs pore width plane, including the isotropic-cholesteric transition, the winding transitions and their complex relationship. In particular, the structure of winding transitions terminates at the capillary isotropic-cholesteric transition via triple points where the confined isotropic phase coexists with two cholesterics with different helix indices. For symmetric and asymmetric monostable plate anchorings the phase diagram are qualitatively similar.

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Section: Introductionmentioning

confidence: 99%

Capillary and winding transitions in a confined cholesteric liquid crystal

2015

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“…Because of this frustration, the confined cholesteric phase forms topological defect structures. Depending on the geometry and anchoring strength, these defects may be elongated string-like objects called cholesteric fingers or helicoids [3][4][5][6][7][8], or they may be localized point-like objects called cholesteric bubbles [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Theory of helicoids and skyrmions in confined cholesteric liquid crystals

Afghah

Selinger

2017

Phys. Rev. E

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Cholesteric liquid crystals experience geometric frustration when they are confined between surfaces with anchoring conditions that are incompatible with the cholesteric twist. Because of this frustration, they develop complex topological defect structures, which may be helicoids or skyrmions. We develop a theory for these structures, which extends previous theoretical research by deriving exact solutions for helicoids with the assumption of constant azimuth, calculating numerical solutions for helicoids and skyrmions with varying azimuth, and interpreting the results in terms of competition between terms in the free energy.

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“…The latter transition arrives either continuously (for a bulk sample) or via a cascade of unwinding transition [18][19][20][21][22] in confined geometry [23]. A generalization of the pitch transitions under a tilted magnetic field in respect to the anchoring direction at the interfaces was recently given in [24].…”

Section: Introductionmentioning

confidence: 99%

Cholesteric pitch-transitions induced by a magnetic field in a sample containing incomplete number of pitches

Lelidis¹,

Barbero

Scarfone

2012

Open Physics

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Abstract:We investigate the pitch transitions induced by an external bulk field in a Cholesteric Liquid Crystal slab of finite thickness that contains an incomplete number of π-twists. The analysis is performed for a magnetic field that is (i) perpendicular to the helical axis, and (ii) tilted with respect to one of the easy directions imposed by planar and rigid boundary conditions. For finite we obtain a cascade of transitions, where the bulk expels a half-pitch at a time with increasing field to avoid divergences in the elastic energy. The dependence of the threshold magnetic field inducing the expulsion on the easy axes twist angle δ is investigated for all the cascade of pitch transitions and in particular for the final one, corresponding to the Cholesteric-Nematic transition. In the → ∞ limit this dependence disappears and we reobtain the results of de Gennes for an infinite sample. PACS

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Static and dynamic properties of cholesteric fingers in electric field

Cited by 143 publications

References 36 publications

Capillary and winding transitions in a confined cholesteric liquid crystal

Capillary and winding transitions in a confined cholesteric liquid crystal

Theory of helicoids and skyrmions in confined cholesteric liquid crystals

Cholesteric pitch-transitions induced by a magnetic field in a sample containing incomplete number of pitches

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