Spin relaxation due to the D'yakonov-Perel' mechanism is intimately related with the spin splitting of the electronic states. We determine the spin relaxation rates from anisotropic spin splittings of electron subbands in n-(001) zinc-blende semiconductor quantum structures calculated selfconsistently in the multi-band envelope function approach. The giant anisotropy of spin relaxation rates found for different spin-components in the (001) plane can be ascribed to the interplay between the bulk and quantum well inversion asymmetry. One of the in-plane relaxation rates may exhibit a striking nonmonotonous dependence on the carrier density.

The D'yakonov-Perel' mechanism, intimately related to the spin splitting of the electronic states, usually dominates the spin relaxation in zinc blende semiconductor quantum structures. Previously it has been formulated for the two limiting cases of low and high temperatures. Here we extend the theory to give an accurate description of the intermediate regime which is often relevant for room temperature experiments. Employing the self-consistent multiband envelope function approach, we determine the spin splitting of electron subbands in n-(001) zinc blende semiconductor quantum structures. Using these results we calculate spin relaxation rates as a function of temperature and obtain excellent agreement with experimental data.

We present spin relaxation times of two-dimensional holes obtained by spin sensitive bleaching of the absorption of infrared radiation in p-type GaAs/AlGaAs quantum wells ͑QWs͒. It is shown that the saturation of intersubband absorption of circularly polarized radiation is mainly controlled by the spin relaxation time of the holes. The saturation behavior has been determined for different QW widths and in a wide range of temperatures with the result that the saturation intensity substantially decreases with narrowing of the QWs. Spin relaxation times are derived from the measured saturation intensities by making use of calculated ͑linear͒ absorption coefficients for direct intersubband transitions. It is shown that spin relaxation is due to the D'yakonov-Perel' mechanism governed by hole-hole scattering. The problem of selection rules is addressed.

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