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 ability to manipulate spin relaxation. Information about the conduction electron spin and mechanisms of spin rotation is incorporated into a Monte Carlo transport simulation program. A model problem, involving linear-in-k splitting 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 ensemble in the 2D channel of finite width. For very wide channels, a conventional 2D value of spin relaxation is obtained. With decreasing channel width, the relaxation time increases rapidly by orders of magnitude. Surprisingly, 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 effectively suppress electron spin relaxation.