Stability of a double twisted structure in spherical cholesteric droplets.

We found for the first time the stabilization of a double twisted structure in cholesteric liquid crystals confined to small spherical droplets under weak anchoring conditions. The direct observation of the droplets using a polarized microscope revealed the physical properties of the structure. The experimental results showed that the stability of the double twisted structure is determined by the relationship between the helical pitch length and the droplet size. We theoretically analyzed the structural stability by the calculation of the Frank elastic free energy including the surface elastic term, and succeeded in explaining the experimental results. In this paper, we concluded that the stability of the double twisted structure is determined by the competition between the surface and the bulk elasticity.