  We report on the observation of spin whirls in a radially expanding polariton
condensate formed under non-resonant optical excitation. Real space imaging of
polarization- and time-resolved photoluminescence reveal a spiralling
polarization pattern in the plane of the microcavity. Simulations of the
spatiotemporal dynamics of a spinor condensate reveal the crucial role of
polariton interactions with a spinor exciton reservoir. Harnessing spin
dependent interactions between the exciton reservoir and polariton condensates
allows for the manipulation of spin currents and the realization of dynamic
collective spin effects in solid state systems.
