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 structure for parameters typical to the 2DEG in GaAs/Al _xGa _{1- x}As heterostructure is calculated. It is found that the periodic modulation potential can modify the single spin excitonic states so strongly, that their lowest energy is no longer the k = 0 spin-exciton (which is unaffected by the periodic potential), but a finite k-state. The energy of this 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.