Slow exciton spin relaxation in single self-assembled In1-xGaxAs/GaAs quantum dots

We calculate the acoustic phonon-assisted exciton spin relaxation via spin-orbit coupling in single self-assembled In1-xGaxAs/GaAs quantum dots using an atomistic empirical pseudopotential method. We show that the transition rate from bright to dark exciton states is zero under Hartree-Fock approximation. The exciton spin relaxation time obtained from sophisticated configuration interaction calculations is approximately 15-55 mu s in pure InAs/GaAs QDs and even longer in alloy dots. These results are more than three orders of magnitude longer than previous theoretical and experimental results (a few ns), but agree with more recent experiments which suggest that excitons have long spin-relaxation times (> 1 mu s).