Magnetically controlled double-twist director configuration of lyotropic chromonic liquid crystals in cylinders: Energetics, topological defects, and instability.

We study experimentally how the double-twist (DT) configuration of cylindrically confined lyotropic chromonic liquid crystals (LCLCs) responds to axial magnetic fields. Our director field model unveils the energetics behind the magnetic-field-induced transition in the twist profile of the DT configuration. Additionally, we catalog three different types of topological defects-residing between the DT domains of opposite handedness-before and after the field application, and propose a new director field model for the defect with a ring disclination. Lastly, we report a symmetry-breaking instability occurring when the field strength exceeds a critical value, suggesting an eccentric DT director field model that reproduces a helixlike optical texture. Our systematic investigation not only enhances our understanding of LCLC energetics but also provides potential for precise control over DT configurations.