Half Vortices in Exciton Polariton Condensates

Abstract

It is shown that vortices in linearly polarized polariton condensates in planar semiconductor microcavities carry two winding numbers ($k$, $m$). These numbers can be either integer or half-integer simultaneously. Four half-integer vortices ($1/2$, $1/2$), ($-1/2$, $-1/2$), ($1/2$, $-1/2$), and ($-1/2$, $1/2$) are anisotropic, possess the smallest energy, and define the Kosterlitz-Thouless transition temperature. The condensate concentration remains finite within the core of the half vortex and the condensate polarization becomes fully circular in the core center.