Spiralling defect cores in chromonic hedgehogs

An elastic quartic twist theory has recently been proposed for chromonic liquid crystals, intended to overcome the paradoxical conclusions encountered by the classical Oseen-Frank theory when applied to droplets submerged in an isotropic fluid environment. However, available experimental data for chromonics confined to cylindrical cavities with degenerate planar anchoring on their lateral boundary can be explained equally well by both competing theories. This paper identifies a means to differentiate these theories both qualitatively and quantitatively. They are shown to predict quite different core defects for the twisted hedgehogs that chromonics generate when confined to a fixed spherical cavity with homeotropic anchoring. In the quartic twist theory, the defect core is estimated to be nearly one order of magnitude larger (few microns) than in the other and, correspondingly, the director field lines describe Archimedean spirals instead of logarithmic ones. [GRAPHICS] .

Automated summary

An elastic quartic twist theory has been proposed to address the inconsistencies encountered by the classical Oseen-Frank theory in chromonic liquid crystals. However, both theories can equally explain experimental data for chromonics confined in cylindrical cavities with degenerate planar anchoring. This paper identifies a way to differentiate these theories by examining the core defects generated by twisted hedgehogs in a fixed spherical cavity with homeotropic anchoring.