Intensity variation of excitons in magnetically tunable double quantum wells

We have studied a series of ZnSe/Zn_1-yCd_ySe double quantum wells coupled by Zn_{1-cursive Greek chi}Mncursive Greek chiSe diluted magnetic semiconductor (DMS) barriers. Such double quantum well systems have the advantage that the height of the barrier separating the wells can be "tuned" by varying an applied magnetic field, providing the experimenter the opportunity to study the effects of coupling between the wells as a function of barrier height continuously in a single structure. In this paper, we discuss a new and rather surprising dependence of the intensities of excitonic transitions observed experimentally as a function of the degree of inter-well coupling. These results can be convincingly explained by the mixing of single-particle states induced by the Coulomb interaction and, consequently, by the formation of intra-well and inter-well excitons. The results clearly indicate that the role of the Coulomb interaction is crucial in establishing the nature of exciton states in these structures.