Coherent control of dephasing process and many-body interactions among excitons in GaAs multiple quantum wells

We show the coherent control of exciton–exciton scattering and dephasing process in GaAs multiple quantum wells by using four-wave mixing measurements. The heavy hole (HH)–light hole (LH) quantum beat has been clearly observed. The quantum beat is suppressed when the delay time of the phase-locked pulses coincides with half the period of the oscillation. The phenomenological dephasing time hardly depend on the suppression or amplification of the quantum beat. However the magnitude of the diffracted signal intensity in the image direction increases (decreases) when the quantum beat is suppressed (amplified). In other words, the dephasing process is suppressed (accelerated) depending on the strength of the HH–LH scattering. We show that the suppression and acceleration of the dephasing process is due to a fifth-order nonlinear effect.