Phys. Rev. Lett. 109, 036404 (2012)

Credit: © APS 2012

Elena Kammann and colleagues from the UK, Singapore, Greece and Russia have demonstrated that polariton spin can be transported over millimetre-scale distances (>300 μm) without significant loss of spin information. As the polaritons propagate, their spins precess around an effective magnetic field in the sample plane; the authors draw analogies to the spin Hall effect. In their studies, the team used an AlGaAs/GaAs microcavity to provide a Rabi splitting of 9 meV and a cavity photon lifetime of 9 ps. To excite the polaritons, a 5-μm laser spot was intensity modulated at 10 kHz and a duty cycle of only 5% was used to reduce heating. Emission from the cavity is separated spectrally from the excitation before imaging. The linear components of the Stokes vector were found to show a cartwheel pattern and the circular component revealed up to four revolutions of the pseudospin around the effective magnetic field within the polariton lifetime. The nonlinear nature of the effect was demonstrated by testing at different powers, revealing a threshold below which the pattern is lost and no spin pattern observed.