Spin repolarization due to Pauli blocking in quantum dots

We have studied the spin dynamics in self-organized InAs/GaAs quantum dots (QD) by time-resolved photoluminescence (PL). After optical orientation of carriers photogenerated in the GaAs barrier by 1.2 ps light pulses, an unex pected increase of the QD excited-state luminescence polarization is observ ed. This effect is interpreted in terms of Pauli blocking which prevents th e relaxation of electrons in the QD ground state already occupied by anothe r electron with the same spin orientation. A theoretical model qualitativel y describing the experimental results is developed.