Colloidal Templating at a Cholesteric-Oil Interface: Assembly Guided by an Array of Disclination Lines

We simulate colloids (radius $R\sim 1\mu \mathrm{m}$) trapped at the interface between a cholesteric liquid crystal and an immiscible oil at which the helical order (pitch $p$) in the bulk conflicts with the orientation induced at the interface, stabilizing an ordered array of disclinations. For a weak anchoring strength $W$ of the director field at the colloidal surface, this creates a template, favoring particle positions either on top of or midway between defect lines, depending on $\alpha =R/p$. For small $\alpha$, optical microscopy experiments confirm this picture, but for larger $\alpha$ no templating is seen. This may stem from the emergence at moderate $W$ of a rugged energy landscape associated with defect reconnections.