Electronic Excitation Transfer Dynamics in a 3-Site System Using an Incoherent Born-Markov Rate Model.

The role of coherence in electronic excitation transfer (EET) dynamics in multi-site systems is typically investigated by comparing results from exact quantum dynamical methods with those derived from incoherent approaches such as the Fermi's Golden Rule (FGR) model. Recent studies on three-site systems have highlighted a remarkable dependence of EET dynamics on intersite coupling for specific configurations. To explore the influence of coherence in such behavior, we adapt the secular Redfield theory to develop an incoherent model by systematically excluding terms that couple populations and coherences in the site basis. The dynamics predicted by this model are then compared with those obtained from the coherent Lindbladian master equation and the incoherent FGR models. This framework provides a general approach for evaluating the role of coherence in a wide range of open quantum systems operating within the weak system-bath coupling regime.