Coherent Multidimensional Optical Spectroscopy of Excitons in Molecular Aggregates; Quasiparticle versus Supermolecule Perspectives

摘要

The results in section 4 are based on the Markovian approximation for the entire response function. The present expressions treat the various time intervals and pathways differently. For the pathways that contain coherences during t2, we maintain the correlated bath dynamics by treating diagonal fluctuations exactly. Second-order perturbation theory with the Markovian approximation is used for offdiagonal fluctuations to get lifetime broadenings. The populations containing pathways during t2 ignore bathfluctuation correlations between different propagation intervals t1, t2, and t3. During t1 and t3, the diagonal fluctuations are treated exactly (by the cumulant expansion). Again, second-order Markovian perturbation theory is made for offdiagonal fluctuations. During t2, second-order Markovian perturbation theory is performed for the coupling with all bath coordinates, which results in the secular Redfield equation.