BAND-STRUCTURE OF THE SPIN EXCITATIONS IN MODULATED HETEROSTRUCTURES UNDER STRONG MAGNETIC-FIELDS

The problem of single spin-excitons in a two-dimensional electron gas (2DEG) under a strong magnetic field, which is subject to artificially generated 1D periodic potentials with periods in the submicron range, is theoretically investigated. The corresponding spin-exciton band st ructure for parameters typical to the 2DEG in GaAs/AlxGa1-As-x heteros tructure is calculated. It is found that the periodic modulation poten tial can modify the single spin excitonic states so strongly, that the ir lowest energy is no longer the k = 0 spin-exciton (which is unaffec ted by the periodic potential), but a finite k-state. The energy of th is state approaches the zero excitation energy at a reasonably strong modulation potential. The corresponding many excitons problem and the possibility of condensation of gapless excitons into a collective spin density wave ground state is briefly discussed.