Transient four-wave-mixing lineshapes due to excitation induced shift and excitation induced dephasing

Summary form only given. In an optically dense material, such as a semiconductor or a dense vapor, many-body interactions can dramatically modify the results of coherent experiments as compared to the dilute limit. The optical Bloch equations (OBE), which are appropriate in the dilute limit, must be modified to include many-body interactions. Such modified OBE (MOBE) are correct for a dense vapor and a phenomenological approximation for semiconductors, where a full treatment is based on the interacting electron-hole Hamiltonian. Previously, terms describing the local field correction (LFC) and excitation-induced dephasing (EID) have been added to the OBE to describe interactions. We show that an excitation-induced shift (EIS) is equally important. Perturbation calculations demonstrate that EIS gives rise to an additional signal in transient four-wave-mixing (TFWM), a common experiment for probing coherence. Comparison to numerical calculations shows that perturbation theory does not adequately describe either EIS or EID.