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usual shape [Fig. 4(d)] has maximum at exciton pumping and (ii) this amplitude increases with increasing of pump power and disappears with decrease of pump power. It allows us to conclude that the main contribution to the RSA signal with shape shown in Fig. 4(d) is due to elec- tron spins polarized by electron-exciton scattering or due to fast spin relaxation of hole in the resonantly excited exciton. 

## V. LOW TEMPERATURE SPIN DYNAMICS 

We turn now to the evolution of the spin dynamics of electrons and holes and in particular to the mecha- nisms providing carrier spin relaxation at extremely low temperatures down to 430 mK. We focus on the Faraday rotation RSA signals measured at the trion resonance, where the hole spin dynamics is most pronounced. Fig- ure 7 shows RSA signals measured at the trion resonance 

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energy for various temperatures. We fit the experimental RSA spectra from Fig. 7 by Eq. (5) and get very good agreement in all cases. The g -factors and spin relaxation times determined in that way are given in the figure cap- tion. 

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The electron and hole spin relaxation times measured at different temperatures are collected in Fig. 8. The data for temperatures below 15 K were determined from RSA spectra and for higher temperatures, at which the RSA signals vanish, we fit the decay of the FR signals at positive delays. The data in the temperature range 

