Exciton coherence in symmetric coupled quantum wells and dots

I calculate exciton states of laterally confined, symmetric, double-quantum-well structures in electric fields to study interwell tunneling and electron-hole Coulomb correlation effects. When correlation is dominant, the zero-field exciton ground state is a coherent state of direct excitons in both wells with enhanced oscillator strength. For increasing field, the ground state becomes direct in a single well and then indirect, and exciton peaks in the absorption spectra evolve asymmetrically.