Superlattice structures observed in the extraordinary phase sequence and analyzed by the phenomenological Landau model and the partially molecular model

Abstract

We draw several electric-field-temperature (E-T ) phase diagrams with electric-field-induced birefringence contours in the nOHFBBB1M7 (n = 10) and nOTBBB1M7 (n = 11) (C11) mixture system by changing the C11 concentration carefully; some of the mixtures show the unusual extraordinary phase sequence where subphases with the four-, five-, and six-layer superlattice structures emerge above the smectic-C * main phase. We try to understand the results in terms of two complementary models that have so far been proposed: the phenomenological Landau model of phase transitions by Dolganov et al. (2003)]. The observed E-T phase diagram can be well reproduced by the phenomenological model. An emergence of the subphase with the four-layer superlattice structure above smectic-C * is also understandable in terms of the partially molecular model. We discuss the pros and cons of the two models as well.

Effective long-range interlayer interactions and electric-field-induced subphases in ferrielectric liquid crystals

“…Subphases with smaller unit cells of irreducible q T in lower terms in the denominator must be observed more easily, whereas those with larger unit cells of irreducible q T in higher terms in both the numerator and denominator may be suppressed by a number of factors including surface and finite-size effects and thermal fluctuations. Experimentally, seven subphases with q T = 1/5, 1/4, 1/3, 2/5, 1/2, 3/5, and 2/3 are considered to exist [1][2][3][4][23][24][25][26][27].…”

“…1 Sequential characteristics of the field-induced transitions have been observed in several temperature-induced subphase regions at zero electric field, q T = 1/4, 1/3, 1/2, 3/5, and 2/3, from the early stage of investigation [1][2][3][4][27][28][29][30][31][32]. All of the antiferroelectric phases, q T = 0 (Sm-C * A ), 1/4, 1/2, and 2/3, must have q E = 0 at zero electric field, whereas ferrielectric and ferroelectric phases, q T = 1/3, 3/5, 2/3, and 1 (Sm-C * ), must have q E = 1/3, 1/5, 1/3, and 1, respectively.…”

“…Sandhya et al recently found a fairly conspicuous example of the field-induced transition from q E = 1/5 (q T = 3/5) to q E = 3/5, which is considered to occur by flipping only one layer in the five-layer unit cell of the temperature-induced subphase with q T = 3/5 [27]. Sandhya et al also observed at least two, probably three field-induced subphases in the transition from q E = 1/3 (q T = 1/3) to q E = 1 (Sm-C * ) [4,32].…”

Transitional subphases near the electric-field-induced phase transition to the ferroelectric phase in Se-containing chiral smectic liquid crystals observed by resonant x-ray scattering

“…Figs. 12 (a) to ( in a unit cell [3,31], is a reasonable layer structure of the subphase appearing between the C 3p (q E = 1/3) and Sm C * (q E = 1) phases. From these considerations, the C 6p subphase observed here is close to the {R 5 L} configuration with a relatively small value of δ, however, the more complicated distorted C 6p structures cannot be ignored.…”

“…antiferroelectric AF (SmC * FI2 , SmC * d4 , or SmC * A (q T = 1/2)), ferrielectric SmC * γ (SmC * FI1 , SmC * d3 , or and other techniques [3,6,[27][28][29][30][31][32]. Recent RXS studies under an electric field directly revealed the electric field-induced phase transitions from the low field AF phase to the high field SmC * γ phases [33][34][35].…”