Spin polarization of quantum Hall states for filling factors 1 ⩽ ν ⩽ 2 measured with microcavity polaritons

Spin polarization measurements were performed in three 2D electron gases in GaAs with densities n e = 9.1 , 7.2 and 6.5 × 10 10 cm⁻², in the quantum Hall regime. Full spin polarization at ν = 1 surrounded by rapid depolarization due to Skyrmion formation was observed in all devices, consistent with past measurements. Depolarization of the ν = 4 / 3 , 8/5 states and repolarization of the ν = 5 / 3 state was also measured, in remarkable agreement with a non-interacting, disorder-free Composite Fermion model. Optical power and temperature dependent measurements of the ν = 1 state suggest a regime of non-linear optics.