Effects of Chiral Dopants on Doubly Twisted Configurations of Lyotropic Chromonic Liquid Crystals in a Cylindrical Cavity*

Confined lyotropic chromonic liquid crystals (LCLCs) often show chiral director configurations despite the absence of intrinsic chirality at the molecular level. For example, nematic LCLCs in a cylindrical cavity with a degenerate planar anchoring exhibit doubly twisted (DT) configurations because of unprecedentedly large saddle-splay-to-twist elasticity ratio. In this work, we investigate how chiral dopants affect this chiral symmetry breaking of LCLCs focusing on the DT configurations in a capillary. We find that, in a cylindrical confinement, the cholesteric LCLCs with a minuscule amount of chiral dopants still show the DT configuration with domains of different handednesses and defects between them. But it becomes homochiral when the dopant concentration is high enough. We characterize these cholesteric DT configurations by optically measured twist angles and provide a simple theoretical model on the energetics of cholesteric DT configurations. Finally, we observe the enantiomeric excess of chiral dopants influence the director configuration when dopants of two different handednesses are mixed.