Spin Relaxation Anisotropy in Two-Dimensional Semiconductor Systems

Spin relaxation is investigated theoretically in two-dimensional systems. Various semiconductor structures of both n- and p-types are studied in detail. The most important spin relaxation mechanisms are considered. The spin relaxation times are calculated taking into account the contributions to the spin--orbit interaction due to both the bulk inversion asymmetry and the structure inversion asymmetry. It is shown that in-plane anisotropy of electron spin relaxation appears in III--V asymmetrical heterostructures. This anisotropy may be controlled by external parameters, and the spin relaxation times differ by several orders of magnitude.