Solitary waves in ferroelectric liquid crystals

The dynamics of bulk molecular reorientation in ferroelectric liquid crystals (FLC's) are modeled by a continuum of elastically coupled, overdamped, massless ferroelectric dipoles under the influence of an external electric field. Numerical solution of this system's equation of motion in one dimension shows that reorientation in response to an applied field step can proceed via the propagation of a solitary wave of universal shape and velocity. Application of the model to an initially helixed configuration shows that solitary waves reorient the bulk only if the applied field is strong enough that its relaxation length is shorter than $\frac{1}{30}$ of the helix pitch. Comparison of our calculations with previous experimental study of the optical response of an FLC indicates that the experimental results cannot be explained by these solitary waves.