WEAK ANTILOCALIZATION AND SPIN PRECESSION IN QUANTUM-WELLS

The results of magnetoconductivity measurements in GaxIn1-xAs quantum wells are presented. The observed magnetoconductivity appears due to t he quantum interference, which lead to the weak localization effect. I t is established that the details of the weak localization are control led by the spin splitting of electron spectra. A theory is developed t hat takes into account both linear and cubic in electron wave-vector t erms in spin splitting, which arise due to the lack of inversion cente r in the crystal, as well as the linear terms that appear when the a;e ll itself is asymmetric. It is established that, unlike spin-relaxatio n rate, contributions of different terms into magnetoconductivity are not additive. It is demonstrated that in the interval of electron dens ities under investigation [(0.98- 1.85) X 10(12) cm(-2)] all three con tributions are comparable and have to be taken into account to achieve a good agreement between the theory and experiment. The results obtai ned from comparison of the experiment and the theory have allowed us t o determine what mechanisms dominate the spin-relaxation in quantum we lls and to improve the accuracy of determination of spin-splitting par ameters in A(3)B(5) crystals and two-dimensional structures.