- dimensional charged - exciton complexes ” by Varga , K – Reply

We respond to criticisms raised by K. Varga (cond-mat/9802262) and reaffirm that the results in our original paper obtained using a two-body analytical method remains valid within the framework of an effective excitonic composite model. The conceptual model of the excitonic systems as well as the numerical method based on variational functions utilized by Varga differ significantly from ours. Hence comparison of binding energies of the charged-biexciton remains questionable. In this reply, we discuss the shortcomings of modelling the charged-biexciton as a five-body system and treating excitonic complexes as atomic systems, as done in Varga's Comment. We also clarify the somewhat misleading statement that the " charged-biexciton complex is stable for any value of the mass ratio " in our original paper and derive a simple criterion for the existence of a single bound charged-biexciton state. In his Comment, Varga has used a AAB-type three-body and AAABB-type five-body system to model the charged exciton and charged biexciton respectively. These excitonic systems have been modelled as an AB type Coulomb problem in our work [1]. This is done by formulating the two-body method (Eqs (15-19) in our original paper) so that a radial Schrodinger equation is obtained in which the potential is not the real two-body potential, but the average potential of a three-or five-body system. With the use of an effective mass and dielectric constant, the resulting radial equation approximates the problem of an exciton complex interacting with holes and electrons in the valence and conducting bands respectively. K. Varga in his Comment has critized this two-body approach and questioned the validity of our results obtained for the charged-biexciton system. We have modelled the charged-biexciton as a two-body system (biexciton + e or h)-justifying calculations based on the analytical expressions derived for the charged exciton (exciton + e or h). The biexciton is conceptualized as a single hydrogenic composite system; the advantage being that experimental estimates of the biexciton binding energy (ref. 19,20 of our paper) can be used to estimate energies of the charged-biexciton complex. Due to the semi-empirical nature of our charged-biexciton model, we firmly disagree with the Comment that an over simplified model has been used in our work. Varga's Comment uses a stochastic variational method based on correlated Guassian basis sets [2]. Unlike the semi-empirical charged biexciton model used in our work, this method treats excitonic systems in solid materials just like atomic systems (e.g. H …