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.

极化子是激子和光子的强耦合产生的混合光-物质准粒子。由于自旋自由度，极化子形成能够在腔平面内长距离传播的自旋流体，具有自旋电子学应用的良好性能。在这里，我们通过使用在Voigt几何体中施加的磁场，通过实验证明了平面微腔中传播的激子-极化子冷凝物的极化动力学的完全控制。我们展示了自旋拍频的变化，光学自旋霍尔效应的抑制以及磁场引起的偏振图案的旋转。