Merging of vortices and antivortices in polariton superfluids

Quantized vortices are remarkable manifestations on a macroscopic scale of the coherent nature of quantum fluids, and the study of their properties is of fundamental importance for the understanding of this peculiar state of matter. Cavity polaritons, due to their double light-matter nature, offer a unique controllable environment to investigate these properties. In this paper we theoretically investigate the possibility to deterministically achieve the annihilation of a vortex with an antivortex through an increase of the polariton density in the region surrounding the vortices. Moreover, we demonstrate that by means of this mechanism an array of vortex-antivortex pairs can be completely washed out.