Longitudinal spin decoherence in spin diffusion in semiconductors

We have set up a set of many-body kinetic Bloch equations with spacial inhomogeneity. We reexamined the widely adopted quasi-independent electron model and showed the inadequacy of this model in studying the spin transport. We further pointed out a new decoherence effect based on interference effect along the diffusion in spin transport problem due to the so called inhomogeneous broadening effect in the Bloch equations. We have shown that this inhomogeneous broadening effect can cause the spin decoherence alone even without the scattering and that the resulting decoherence is more important than the dephasing effect due to the D'yakonov-Perel' (DP) term together with the scatterings.