Spectral Road Map of Strain-Split Bulk GaAs Excitons: Evidence of Excitation-Induced Dephasing

Thin films of bulk GaAs studied with two-dimensional coherent spectroscopy reveal strain-split heavy- (HH) and light-hole (LH) excitons with quantum interference. Excitation overlapping the HH continuum show strong excitation-induced dephasing (EID) and emission at the HH exciton for collinear polarization. The results are consistent with excitations beyond the perturbative $\chi^{(3)}$ regime. Cross-linear polarization suppresses the HH emission and enhances the LH exciton as well as HH biexciton emission. Two-quantum spectra at low excitation concentrations are also consistent with HH and LH exciton interference and EID. Results are compared to four-wave mixing transients that require modelling for interpretation.