Magnetic control of polariton spin transport

Polaritons are hybrid light-matter quasiparticles arising from the strong coupling of excitons and photons. Owing to the spin degree-of-freedom, polaritons form spinor fluids able to propagate in the cavity plane over long distances with promising properties for spintronics applications. Here we demonstrate experimentally the full control of the polarization dynamics of a propagating exciton-polariton condensate in a planar microcavity by using a magnetic field applied in the Voigt geometry. We show the change of the spin-beat frequency, the suppression of the optical spin Hall effect, and the rotation of the polarization pattern by the magnetic field. The observed effects are theoretically reproduced by a phenomenological model based on microscopic consideration of exciton-photon coupling in a microcavity accounting for the magneto-induced mixing of exciton-polariton and dark, spin-forbidden exciton states.