The effect of melting on the electrostatic coherence length of nematic liquid crystals

We examine the effects of electric field induced changes in molecular order on the director structure within a nematic liquid crystal cell. Specifically, we investigate the boundary layer between the cell substrate and the bulk nematic material when strong anchoring forces the nematic director in a different direction to that of an applied field. We find that at low field strengths the classical picture of liquid crystal/electric field interaction occurs, that is, the director orientation is governed by the surface alignment until a transition occurs as the classic electrostatic coherence length zeta becomes comparable to the cell thickness and the director changes orientation so as to align with the electric field. However, at high field strengths, we find that a field induced change of the molecular order close to the cell boundary causes a significant reduction, to 0(zeta²), in the effective electrostatic coherence length, i.e. the characteristic length of the director distortion.