Spin-dependent analysis of homogeneous and inhomogeneous exciton decoherence in magnetic fields

This paper discusses the combined effects of optical excitation power, interface roughness, lattice temperature, and applied magnetic fields on the spin coherence of excitonic states in GaAs/AlGaAs multiple quantum wells. For low optical powers, at lattice temperatures between 4 and 50 K, the scattering with acoustic phonons and short-range interactions appear as the main decoherence mechanisms. Statistical fluctuations of the band gap, however, become also relevant in this regime and we were able to deconvolute them from the decoherence contributions. The circularly polarized magneto-photoluminescence unveils a nonmonotonic tuning of the coherence for one of the spin components at low magnetic fields. This effect has been ascribed to the competition between short-range interactions and spin-flip scattering, modulated by the momentum relaxation time.