Modulated smectic C*-uniform smectic C* phase transition in an electric field

Abstract

A detailed analytic description of the phase transition in an electric field between the modulated smectic C chiral phase and the uniform smectic C chiral phase is given taking into account both ferroelectric and dielectric coupling to the field in the case of negative anisotropy. Within the Landau theory of phase transitions we find helix distortions, and establish the field dependence of the pitch and the phase boundaries in the E-T phase diagram. The transition considered here is continuous. The evolution of the polarization and susceptibility with the field is described as well as domain walls in the uniform phase. The fluctuation spectrum for some values of the field also contains, besides the usual phason and phonon branches, a new oscillatory branch. The disappearance of the walls occurs through unwinding in our model but we also suggest a possible mechanism through line defects