Identification of higher-order electronic coherences in semiconductors by their signature in four-wave-mixing signals

Four-wave-mixing signals from excitons under linear-circular polarized exci tation exhibit an elliptical polarization, depending on both the pulse dela y and the spectral position. Besides the resonances corresponding to excito ns and exciton-biexciton transitions, a breakup of the exciton line is foun d reflecting the influence of correlations on the four-point level. An anal ysis accounting for the exciton density, the bound biexciton, and the excit on-exciton scattering continuum reveals that these features are not due to an antibound two-exciton state. Instead, they result from an interference o f the correlated exciton continuum with the exciton density. In addition, t he modeling shows that the signals ellipticity is highly sensitive to the i nfluences of different correlations and, therefore, allows for a discrimina tion of their contributions.