Vortexlike Topological Defects in Nematic Colloids: Chiral Colloidal Dimers and 2D Crystals

We show that chiral ordering of the underlying complex fluid strongly influences defect formation and colloidal interactions. Nonsingular defect loops with a topological charge -2 are observed, with a cross section identical to hyperbolic vortices in magnetic systems. These loops are binding spontaneously formed pairs of colloidal particles and dimers, which are chiral objects. Chiral dimer-dimer interaction weakly depends on the chirality of dimers and leads to the assembly of 2D nematic colloidal crystals of pure or mixed chirality, intercalated with a lattice of nonsingular vortexlike defects.