Spin relaxation in semiconductor quantum dots

We have studied spin-flip processes in GaAs electron quantum dots that accompany transitions between different discrete energy levels. Several different mechanisms that originate from spin-orbit coupling are shown to be responsible for such processes. We have evaluated the rates for all mechanisms with and without a magnetic field. We have shown that the spin relaxation of the electrons localized in the dots differs strikingly from that of the delocalized electrons. The most effective spin-flip mechanisms related to the absence of the inversion symmetry appear to be strongly suppressed for localized electrons. This results in unusually low spin-flip rates.