  In-plane magnetic field is found to change drastically the photoluminescence
spectra and kinetics of interwell excitons in GaAs/AlGaAs coupled quantum
wells. The effect is due to the in-plane magnetic field induced displacement of
the interwell exciton dispersion in a momentum space, which results in the
transition from the momentum-space direct exciton ground state to the
momentum-space indirect exciton ground state. In-plane magnetic field is,
therefore, an effective tool for the exciton dispersion engineering.
