On the identification of intervalence-band coherences in semiconductor quantum wells

A theoretical analysis of intervalence-band coherences is presented. These optically created nonradiative coherences are generalizations of non-radiat ive coherences in atomic and molecular three-level systems. Whereas in thre e-level systems these coherences are the basis of important and well-establ ished nonlinear effects, the interpretation of experimental evidence for su ch coherences in semiconductors needs to be supported by many-body theory. Based on the dynamics-controlled truncation formalism, the respective contr ibutions of intervalence-band coherences and coherent biexcitonic correlati ons in time-integrated differential transmission spectroscopy is investigat ed. It is found that the contribution of the biexcitonic correlations to th e observable heavy-hole-light-hole beats can be eliminated, either by reduc ing the light pulse duration or by choosing the central frequency of the li ght pulses at the heavy-hole exciton.