“…Such a singlet-triplet crossover can either be observed directly, as a crossing of the corresponding optical lines, e.g., in emission spectra, or it may be hidden and affect only the intensities of these transitions. 7 A comprehensive spectroscopic study, involving the analysis of circularly polarized emission, absorption, and reflectivity spectra is required, in order to get a reliable separation of the Coulomb and Zeeman contributions to the trion binding energies. Such an analysis is hampered by the fact that the hole Zeeman splitting in QWs is typically a nonlinear function of the magnetic field strength and, as such, is not described by a field-independent g factor, as shown below.…”