Proposal for the temperature-electric-field phase diagram of a ferroelectric smectic-C* liquid crystal.

We report on the results of extensive optical measurements on the ferroelectric smectic-C* phase of the chiral liquid crystal 4-(2(') methyl butyl) phenyl 4(')-n-octylbiphenyl-4-carboxylate. We have explored the entire temperature-electric-field phase space searching for all possible phase transitions in the C* region and have characterized them both as to their character, including whether they are first or second order, and also whether they are of instability or nucleation type. Our results lead us to conclude that the experimental phase diagram is incompatible with all existing theoretical models for the C* phase transitions. We propose instead a phase diagram where two second-order lines and one first-order line meet at a triple point that we tentatively identify as a Lifshitz point.