Indirect exciton spin relaxation in semiconductor quantum wells

It is considered here the problem of the microscopic theory of the indirect exciton spin relaxation in III-V semiconductor quantum wells. The direct exciton spin relaxation is that between the optical active states driven by the electron-hole exchange interaction. In the indirect case the heavy-hole exciton spin is flipped after sequential spin flips of the single particles. We show that this relaxation channel is driven by the k e3 spin-orbit splitting in the conduction band due to inversion asymmetry. Adding such interaction to the exciton Hamiltonian we obtain an effective exciton spin Hamiltonian corresponding to a pseudo spin 1/2 in an effective Koarr-dependent magnetic field, which changes randomly with elastic scattering of the center-of-mass momentum Koarr. It describes the exciton-bound electron spin dynamics, and allows the calculation of the relaxation rate (W e), that limits the exciton spin relaxation rate in the indirect channel. We obtain W e as a function of the material and structure parameters. The estimated values are shown to be in good accord with the available experimental data