Lagoudakis, K. G.Ostatnický, T.Kavokin, A. V.Rubo, Y. G.André, R.Deveaud-Plédran, B.2009-11-152009-11-152009-11-15200910.1126/science.1177980https://infoscience.epfl.ch/handle/20.500.14299/44237WOS:000271712300034Singly quantized vortices have already been observed in many systems, including the superfluid helium, Bose-Einstein condensates of dilute atomic gases, and condensates of exciton-polaritons in the solid state. Two-dimensional superfluids carrying spin are expected to demonstrate a different type of elementary excitations referred to as half-quantum vortices, characterized by a (pi) rotation of the phase and a (pi) rotation of the polarization vector when circumventing the vortex core. We detect half-quantum vortices in an exciton-polariton condensate by means of polarization-resolved interferometry, real-space spectroscopy, and phase imaging. Half-quantum vortices coexist with single-quantum vortices in our sample.POLARITONSCONDENSATIONUNCONVENTIONAL VORTICITYtext::journal::journal article::research article