Zigzag instability of a chi disclination line in a cholesteric liquid crystal

Alain Dequidt (1) , Patrick Oswald (1)

1 Phys-ENS - Laboratoire de Physique de l'ENS Lyon

We studied the formation of chi disclination lines in planar cholesteric samples placed in a temperature gradient near the cholesteric to smectic A phase transition. We observed that the first simple line which forms close to the smectic-cholesteric front zigzags when it is perpendicular to the direction of planar anchoring and is straight for other orientations. This instability is similar to Herring instability for crystalline surfaces. We show numerically that it originates from a strong increase of the elastic anisotropy close to the transition. In addition, we propose a new method to measure the pitch divergence at the smectic to cholesteric phase transition.

Keywords: Liquid crystals; Cholesteric; Pitch divergence; Disclination line; Zigzag instability

Domains: Physics [physics]; Condensed Matter [cond-mat]; Soft Condensed Matter [cond-mat.soft]

Alain Dequidt, Patrick Oswald. Zigzag instability of a chi disclination line in a cholesteric liquid crystal. European Physical Journal E: Soft matter and biological physics, 2006, 19 (4), pp.489-500. ⟨ensl-00182727⟩