Ferroelectric-antiferroelectric phase transition in a two-molecular-layer free-standing liquid-crystal film

Free-standing films of a smectic liquid crystal possessing the bulk phase sequence smectic A, ferroelectric smectic C, antiferroelectric smectic ${\mathit{C}}_{\mathit{A}}$ are studied. Using ellipsometric measurements, we show that the bulk phases still exist in films consisting of only four, three, and even two smectic layers, i.e., the phase transition from the ferroelectric smectic-C phase to the antiferroelectric smectic-${\mathit{C}}_{\mathit{A}}$ phase in the three- and two-layer films is characterized by the inversion of the tilt and polarization direction in a single smectic layer.