Mean-Field to Tricritical Crossover Behavior near the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">Smectic</mml:mi><mml:mo>−</mml:mo><mml:mi>A</mml:mi><mml:mo>−</mml:mo><mml:mi mathvariant="normal">Smectic</mml:mi><mml:mo>−</mml:mo><mml:mrow><mml:msup><mml:mrow><mml:mi>C</mml:mi></mml:mrow><mml:mrow><mml:mo>*</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>Tricritical Point

Shashidhar, R.; Ratna, Banahalli R.; Nair, Geetha G.; Prasad, S. Krishna; Bahr, Christian; Heppke, G.

doi:10.1103/physrevlett.61.547

Cited by 71 publications

(43 citation statements)

References 15 publications

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“…This binary mixture exhibits AC * transition which is between first order (pure C7) and second order, as observed experimentally [1,2]. A tricritical point (TCP) exists in this binary mixture for its AC * transition.…”

Section: Introductionmentioning

confidence: 71%

“…As the concentration increases in a binary mixture of liquid crystals, a first order smectic A-smectic C (AC) or AC * transition changes toward a second order one, as observed experimentally in some binary mixtures such as C7 + 70PDOB [1,2], C7 + 10.O.4 [3,4] and SCE9 + SCE10 [5]. This has been demonstrated using the mean field models with the biquadratic coupling (P 2 θ 2 ) [6,7] and P 2 θ 2 + Pθ (bilinear) coupling in our recent studies [8][9][10][11], in particular for the binary mixtures of C7 + 10.O.4 [8], SCE9 + SCE10 [9,10] and C7 + 70PDOB [11].…”

Section: Introductionmentioning

confidence: 85%

“…In the free energy expansion for the mean field models, the tilt angle is considered as a primary order parameter θ , whereas the spontaneous polarization P is the secondary order parameter and their temperature dependence can be derived by minimizing the free energy. Experimental studies have indicated that the AC * transition is mainly due to intermolecular forces which produce the smectic C phase and that a ferroelectric coupling between permanent dipoles is weaker [15][16][17] as also pointed out previously [1,2].…”

Section: Introductionmentioning

confidence: 93%

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Analysis of the Tilt Angle for a Binary Mixture of C7-70PDOB Liquid Crystal Close to the Smectic A–Smectic C* Transition

Kurt¹,

Avcı

2014

Ferroelectrics

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The tilt angle θ is calculated as a function of temperature close to the smectic A-smectic C * (AC * ) transition for the liquid crystal C7 and its binary mixtures of 70PDOB with the concentrations (mol %) of X = 0, 5. 15, 9.68, 15.0 and 19.4. The experimental data from the literature are analyzed for these binary mixtures using the mean field models with the free energies expanded in terms of the order parameters (tilt angle θ and the spontaneous polarization P). In the mean field models, the biquadratic P 2 θ 2 and P 2 θ 2 + Pθ (bilinear) couplings are considered, and the coefficients in the expansion are calculated for the concentrations X (70PDOB) in this binary mixture of C7+70PDOB. Our mean field predictions are satisfactory and they explain the observed behaviour in this liquid crystalline system.

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Section: Introductionmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 93%

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Analysis of the Tilt Angle for a Binary Mixture of C7-70PDOB Liquid Crystal Close to the Smectic A–Smectic C* Transition

Kurt¹,

Avcı

2014

Ferroelectrics

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“…11 Compounds having high polarization ͑P s ͒ were considered to exhibit a first order Sm C * -Sm A phase transition. 12,14,15 Experimentally, it was shown that the Sm C * -Sm A phase transition was mainly driven by intermolecular forces producing the Sm C * phase. [16][17][18] However, some compounds having a smaller Sm A phase 10 or no Sm A phase 19 and small P s have also shown a second order Sm C * -Sm A phase transition.…”

Section: Introductionmentioning

confidence: 99%

Effect of smectic A temperature width on the soft mode in ferroelectric liquid crystals

Choudhary¹,

Kaur²,

Prakash³

et al. 2008

Journal of Applied Physics

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The behavior of soft mode range with respect to the temperature width of smectic A ͑Sm A͒ phase has been studied in four different ferroelectric liquid crystal ͑FLC͒ materials in the frequency range 10 Hz-10 MHz. The studies have been carried out in a planarly well aligned cells at different temperatures and different bias fields in Sm C * and Sm A phases. Dielectric studies of these FLCs near Sm C * -Sm A phase transition show that the temperature range of soft mode relaxation frequency phenomenon varies with the temperature width of Sm A phase. The dependence of tilt angle on temperature shows the nature of the order of transition at Sm C * -Sm A phase. The coupling between order parameters of Sm C * and Sm A phase influences the soft mode and phase transition in Sm C * and Sm A phases.

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“…The first is the coupling of the tilt to biaxiality, which in chiral systems is related to the size of spontaneous polarization [3,4]. The second is the width of the A phase [5].…”

mentioning

confidence: 99%

de Vries Behavior in Smectics near a Biaxiality Induced Smectic A – Smectic C Tricritical Point

Saunders

2009

Molecular Crystals and Liquid Crystals

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We show that a generalized Landau theory for the smectic A and C phases exhibits a biaxiality induced AC tricritical point. Proximity to this tricritical point depends on the degree of orientational order in the system; for sufficiently large orientational order the AC transition is 3D XY like, while for sufficiently small orientational order, it is either tricritical or 1st order. We investigate each of the three types of AC transitions near tricriticality and show that for each type of transition, small orientational order implies de Vries behavior in the layer spacing, an unusually small layer contraction. This result is consistent with, and can be understood in terms of, the ''diffuse cone'' model of de Vries. Additionally, we show that birefrin gence grows upon entry to the C phase. For a continuous transition, this growth is more rapid the closer the transition is to tricriticality. Our model also predicts the possibility of a nonmontonic temperature dependence of birefringence.

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Mean-Field to Tricritical Crossover Behavior near theSmectic−A−Smectic−C*Tricritical Point

Abstract: Precise x-ray measurements of the tilt angle near the smectic-^4-smectic-C* tricritical point show clear evidence of mean-field to tricritical crossover behavior; the mean-field region shrinks to zero at the tricritical point.

Cited by 71 publications

References 15 publications

Analysis of the Tilt Angle for a Binary Mixture of C7-70PDOB Liquid Crystal Close to the Smectic A–Smectic C* Transition

Analysis of the Tilt Angle for a Binary Mixture of C7-70PDOB Liquid Crystal Close to the Smectic A–Smectic C* Transition

Effect of smectic A temperature width on the soft mode in ferroelectric liquid crystals

de Vries Behavior in Smectics near a Biaxiality Induced Smectic A – Smectic C Tricritical Point

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