Frustration between Ferroelectricity and Antiferroelectricity in Extremely Soft Chiral Smectic-C Like Phases of Liquid Crystals

Abstract

In a group of compounds that exhibit antiferroelectric and/or ferrielectric liquid crystal phases, the bent molecular shape has been considered to cause unique interactions among smectic layers. The interactions are responsible for the successive phase transitions as described by the devil's staircase and the V-shaped switching, which are related with the interlayer ordering and the diminished tilting correlation, respectively. These two are apparently contradictory each other, but result from the same cause, i.e. frustration between ferroelectricity and antiferroelectricity in the Sm-C* like phase. The ANNNI model Yamashita and Miyazima introduced has been shown to describe the frustration appropriately provided that we undertake some refinements: the Ising spin corresponding to the tilting sense of the local in-plane director, the X-Y character of the spin, the tilt angle decrease toward Sm-A, and most importantly, the reassignment of the pseudo-spin to the biasing direction of the molecular rotation about their long axis.

Key Words:

• bent molecular shape
• devil's staircase
• disordered chiral smectic-C like phase
• V-shaped switching
• frustration between ferro- and antiferroelectricity
• ANNNI model