Degeneracy lifting near the frustration points due to long-range interlayer interaction forces and the resulting varieties of polar chiral tilted smectic phases

Abstract

To gain a clear understanding of ferroelectricity and antiferroelectricity together with their frustration in chiral tilted smectic liquid crystals, we have constructed E–T phase diagrams by drawing field-induced birefringence contours in the prototype binary mixture system of MHPOCBC and MHPOOCBC. The results obtained are discussed in terms of the theoretical model proposed by Emelyanenko and Osipov; we have insisted on the appropriateness of specifying the biaxial subphases, which emerge sequentially in the temperature-induced transition, by the relative ratio of ferroelectric and antiferroelectric orderings in the superstructure unit cell, such as , where q_T  = [F]/([A] + [F]). Additional subphases other than the ordinary subphases with three- and four-layer superstructures, and , have been established to exist, firmly for and less adequately for and . Likewise, we have observed several stable superstructures during the field-induced transition from the biaxial subphases to unwound SmC*, and have tried to specify them using q_E  = |[R] − [L]|/([R] + [L]), where [R] and [L] refer to the numbers of smectic layers with directors tilted to the right and to the left, respectively, in a unit cell of the superstructure. We have also found the characteristic field-induced deformation of the uniaxial subphase and attempted to understand it in terms of the devil's staircase due to soliton condensation reported recently by Torikai and Yamashita ( 41 ).

Keywords:

• chiral tilted smectics
• ferroelectricity
• antiferroelectricity
• frustration
• subphase

Acknowledgements

We are pleased to contribute a paper, stimulated by de Gennes's basic idea of frustration, to this special issue of Liquid Crystals. We would like to acknowledge Mamoru Yamashita for enlightening discussions about the unwinding process of as the condensation of discrete solitons. We are grateful to the Irish Research Council of Science, Engineering and Technology (IRCSET) for the award of a postdoctoral Fellowship to K. L. Sandhya for 2006–08. The experimental facilities were funded by the SFI (grant no. 02/IN.1/I031).