Birth and annihilation of topological defects on the nematic–isotropic interface during droplet coalescence

In our work, we for the first time observed simultaneous birth and subsequent annihilation of two types of defects on nematic–isotropic interface: point boojums and localised equatorial defects. The investigations were made in the two-phase nematic–isotropic region in nematic droplets with conical boundary conditions. We found a new type of localized defects formed from equatorial ring defects in confined geometry of planar optical cells. During coalescence of nematic droplets, we observed formation of four antipodes of boojums and localised equatorial defects, followed by their pairwise annihilation with existing defects. The dynamics of defect annihilation was investigated.