Coherence versus Coulomb scattering in resonantly excited quantum wells

The role of Coulomb scattering is studied in the coherent transients of str ongly driven exciton resonances in semiconductor quantum wells. Coulomb sca ttering is treated within the second Born approximation and the light-induc ed dressing of the electron-hole gas is consistently included. The light dr essing is found to decrease the Coulomb collision efficiency and therefore the field-driven dynamics is close to the Hartree-Fock case. Indeed, Coulom b relaxation and dephasing are not strong enough to prevent a dynamical Sta rk splitting in the pump-probe absorption spectra.