Three-pulse photon-echo spectroscopy as a probe of the photoexcited electronic state manifold in coupled electron-phonon systems

We demonstrate that a three-pulse photon-echo technique is capable of eliminating the effect of the absorption band broadening associated with intrinsic electron-phonon coupling, and revealing its structure determined by the optical transitions between the ground and excited electronic states dressed with vibrational quanta. This is important for the spectroscopic probing of photoexcited dynamics in low-dimensional materials with strong electron-phonon coupling. As a minimal model for our calculations, we use a two-electron, two-site Holstein Hamiltonian accounting for the vibrational degree of freedom fully quantum mechanically.