Evolution of Subphases in a Prototype Binary Mixture System as Observed by Electric-Field-Induced Birefringence and Helical Pitch K. L. Sandhya, Atsuo Fukuda, and J. K. Vij Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Dublin, Ireland We have constructed the E–T phase diagrams by drawing the field-induced birefringence contours in the prototype MHPOCBC and MHPOOCBC binary mixture system. The obtained subphase evolution in the diagrams clearly indicate that there exist some additional biaxial subphases other than the ordinary ones with three- and four-layer superstructures, and that the field-induced deformation of uniaxial SmC  a in MHPOCBC occurs quite differently in the high and low tem- perature regions. We have discussed the origin and structures of the additional subphases and different types of the field-induced deformations in terms of the extended Emelyanenko-Osipov model together with the Devil’s staircase character of field-induced unwinding process of the SmC  a short-pitch helical structure pub- lished by Yamashita et al. in these Proceedings. Keywords: anti ferroelectric and ferroelectric liquid crystals; chiral smectics; mixtures of chiral smectics; temperature driven and electric field induced subphases I. INTRODUCTION Tilted smectic liquid crystals most commonly emerge as the synclinic SmC phase, where the directors tilt in the same direction in all layers. The anticlinic SmC A phase with the tilt direction alternating from layer to layer has been observed in more restricted smectic materials. When the tilted smectic phases are chiral, these are designated as SmC  and SmC  A ; the director shows a helical structure and each smectic layer pos- sesses a spontaneous polarization perpendicular to the tilt plane with a sign determined by the tilting sense. Consequently, SmC  and SmC  A are The authors thank M. Yamashita (Mie University, Japan) for the discussions. SFI and IRCEST are thanking for a partial funding of the work. K. L. Sandhya thanks the IRCEST for the award of a post-doctoral fellowship. Address correspondence to J. K. Vij, Department of Electronic and Electrical Engi- neering, Trinity College, University of Dublin, Dublin 2, Ireland. E-mail: jvij@tcd.ie Mol. Cryst. Liq. Cryst., Vol. 511, pp. 36=[1506]–49=[1519], 2009 Copyright # Taylor & Francis Group, LLC ISSN: 1542-1406 print=1563-5287 online DOI: 10.1080/15421400903048537 36=[1506]