Progressive suppression of spin relaxation in two-dimensional channels of finite width

We have investigated spatiotemporal kinetics of electron spin polarization in a semiconductor narrow two-dimensional (2D) strip and explored the abili ty to manipulate spin relaxation. Information about the conduction electron spin and mechanisms of spin rotation is incorporated into a Monte Carlo tr ansport simulation program. A model problem, involving linear-in-k splittin g of the conduction band responsible for the D'yakonov-Perel' mechanism of spin relaxation in the zinc-blende semiconductors and heterostructures, is solved numerically to yield the decay of spin polarization of an electron e nsemble in the 2D channel of finite width. For very wide channels, a conven tional 2D value of spin relaxation is obtained. With decreasing channel wid th, the relaxation time increases rapidly by orders of magnitude. Surprisin gly, the crossover point between 2D and quasi-1D behavior is found to be at tens of electron mean-free paths. Thus, classically wide channels can effe ctively suppress electron spin relaxation.