Zigzag Disclinations in Biaxial Nematic Liquid Crystals

Disclination lines are observed in the biaxial nematic phase of the lyotropic system comprised of rubidium laurate, 1-decanol, and ${\mathrm{H}}_2$O. They are shown to have a uniaxial nematic core which couples to the anisotropic elastic field produced by the surrounding medium. This interaction makes the disclination lines tilt and break into zigzags. The tilt angle is measured in the vicinity of the uniaxial to biaxial nematic phase transition, and found to vary linearly with temperature, which is consistent with the classical behavior of this phase transition.