Propagating electroconvection in nematic liquid crystals under DC excitation

Abstract

On the basis of a simple one-dimensional linear model we show for the first time that a propagating electrohydrodynamic instability (PI) of a nematic liquid crystal occurs at the threshold of DC excitation if the symmetry of a homogeneously aligned cell is changed by introducing a small (~ 0.01 rad) pre-tilt of the director. Flexoelectric torques, which are π/2 out of phase with those produced by other couplings, provide the driving mechanism for the PI mode, whose direction depends on that of the applied field. We also report an experimental observation of this mode.