  We model spin blockade for optically excited electrons and holes in a charged
semiconductor quantum dot. We study the case where the quantum dot is initially
charged with a single electron and is then filled with an additional, optically
excited electron-hole pair, thus forming a charged exciton (trion). To make
contact with recent experiments, we model an optical pump-probe setup, in which
the two lowest quantum dot levels (s and p shells) are photo excited. Using the
Lindblad master equation, we calculate the differential transmission spectrum
as a function of the pump-probe time delay. Taking into account both spin
conserving and spin-flip intraband relaxation processes, we find that the
presence of the ground-state electron spin leads to an optical spin blockade at
short delay times which is visible as a crossover between two exponential
decays of the differential transmission. To make predictions for future
experiments, we also study the dependence of the spin-blockade on an external
magnetic field.

Mesoscale and Nanoscale Physics