Zigzag instability of a c disclination line in a cholesteric liquid crystal
We studied the formation of C 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 showed numerically that it originates from a strong increase of the elastic anisotropy close to the transition. In addition, we proposed a new method to measure the pitch divergence and the associated critical exponent at the smectic to cholesteric phase transition.
Image: Zigzag instability of a c line.
A. Dequidt, P. Oswald, Zigzag instability of a C disclination line in a cholesterric liquid crystal, Eur. Phys. J. E, 19 (2006) 489.
P. Oswald, A. Dequidt, A Zywocinski, Sliding planar anchoring and viscous surface torque in a cholesteric liquid crystal, Phys. Rev. E, 77 (2008) 061703.