Interaction induced dephasing of excitons in wide ZnSe/ZnMgSe single quantum wells

The dephasing of excitons in wide ZnSe/Zn0.94Mg0.06Se single quantum wells (SQW) is investigated by spectrally resolved, time integrated four-wave mixing (FWM). Simultaneous excitation of Is center-of-mass quantized heavy-hole and light-hole excition states leads to pronounced quantum beats. Polarization-dependent measurements identify a biexcition formation of the 11h exciton showing a binding energy of E-BX = 3.5 +/- 0.5 meV. The measurements also indicate, that the third-order polarization is strongly influenced by interaction-induced processes. We show, that excitation-induced dephasing gives the main contribution for co-polarized excitation, followed by the conventional density grating mechanism, while local fields play a subordinate role. (C) 1998 Published by Elsevier Science B.V. All rights reserved.