Influence of electric field on a first-order smectic-<i>A</i>–ferroelectric-smectic-<i>C</i>liquid-crystal phase transition: A field-induced critical point

Abstract

The observation of a new critical point in liquid-crystal phase transitions is reported. Detailed tilt-angle, polarization, and susceptibility measurements of a ferroelectric liquid-crystal compound in the presence of an applied dc electric field show that a first-order phase transition between the polarized smectic-A phase and the ferroelectric-smectic-C phase terminates at a critical point in the temperature field plane. A liquid-crystal sample exhibiting a second-order smectic-A--ferroelectric-smectic-C transition is studied by similar measurements demonstrating a clearly different behavior to the first-order compound. A simple Landau description of the new critical point is given.