Circular polarization reversal of half-vortex cores in polariton condensates

Vortices are topological objects carrying quantized orbital angular momentum and have been widely studied in many physical systems for their applicability in information storage and processing. In systems with spin degrees of freedom, the elementary excitations are so-called half vortices, carrying a quantum rotation only in one of the two spin components. We study the spontaneous formation and stability of such localized half vortices in semiconductor microcavity polariton condensates, nonresonantly excited by a linearly polarized ring-shaped pump. The TE-TM splitting of optical modes in the microcavity system leads to an effective spin-orbit coupling, resulting in solutions with discrete rotational symmetry. The cross-interaction between different spin components provides an efficient method to realize all-optical half-vortex core switching, inverting its circular polarization state. This switching can be directly measured in the polarization-resolved intensity in the vortex core region and it can also be applied to higher order half-vortex states.