Light Scattering From a Nematic Liquid Crystal in the Presence of an Electric Field

Abstract

Abstract The intensity and spectrum of light scattered by a nematic liquid crystal of positive dielectric anisotropy (5CB) in the presence of an ac squarewave electric field have been measured. The results for the twist-bend mode agree well with the theory developed by the Orsay Group and lead to satisfactory values for elastic and viscous coefficients. The results for the splay-bend mode, however, do not, showing a strong dependence on the frequency of the applied field, with scattering no longer of Lor-entzian form. In an attempt to explain the above we examine appropriate solutions of the continuum equations including both conduction and flexoelectric effects. In line with our experimental results, it turns out that neither of these complications affects the twist-bend mode, but that both contribute to the splay-bend mode, although the influence of llexoelectricity is likely to be small. However, conduction can significantly alter the splay-bend mode, there being the possibility of a more complex behaviour when this additional effect is included, which appears to explain the observed non-Lorentzian response.