Illustration from Scientific Research

Possible quantum pathways considering the non-rephasing contributions ( ω τ > 0 and ω t > 0) of the third-order polarization for the interacting electron–phonon system. The green arrow denotes the interaction with the THz pulse, the two red arrows denote the two-photon process caused by the NB and BB pulses, and the blue arrow denotes the emission. Interband transitions can involve multiphonon excitations because of the EPC.

DOI