Coherent signature of differential transmission signals in semiconductors: Theory and experiment

Transient pump-probe signals of a GaAs/Alₓ{Ga}_{1{{-}}x}$As quantum well are investigated both theoretically and experimentally for different excitation conditions. The calculations are based on a microscopic density-matrix approach taking higher-order correlations into account. We present spectrally resolved transients which provide insights into the nature of the differential transmission change. Especially the complex phase signature of heavy-hole--light-hole quantum beats in dependence of the detection energy allows for an identification of different microscopic processes in the pump-probe signal. The theoretical results are verified experimentally by comparison with the coherent and incoherent parts of the time-resolved data. We find a dominant role of the Coulomb-induced correlations up to the χ⁽³⁾ relevant four-point level in the coherent signature in comparison to the Pauli blocking contributions.