Suppressed electron-hole exchange spin flip in cavity polaritons

We consider theoretically the spin relaxation of exciton-polaritons in semiconductor microcavities in the strong coupling regime. The dominant quantum well exciton polarization relaxation mechanism is typically due to the long-range intra-exciton electron-hole exchange. We estimate perturbatively the corresponding contribution for the lower polaritons as a function of the elastic scattering time in analogy to the Dyakonov-Perel model for electron spin relaxation. We find a strong suppression of the polariton spin flip rate due to the electron-hole exchange with respect to the quantum well exciton case.