Analysis of bridge-mediated pathways for long-range charge transfer systems

With the density matrix decomposition scheme of the path integral method, an accurate quantitative analysis on bridge-mediated pathways in long-range charge transfer processes is presented. Unlike a donor-bridge-acceptor triad, a long-range charge transfer process with a number of bridges has additional pathways in which charges always migrate through bridges but not necessarily by incoherent nearest-neighbor hopping. By employing the density matrix decomposition and sorting the incoherent nearest-neighbor and the coherent next-nearest-neighbor hopping pathways, respective contributions to the charge transfer are evaluated quantitatively. Numerical results of two series of configurations with varying degrees of coherence within the system have found that, depending on the configuration, the contribution of the coherent pathways other than superexchange pathways is significant. In the presence of the coherence, long-range charge transfer dynamics may be dominated by the through-bridge mechanism that consists of the coherent through-bridge pathways as well as the incoherent nearest-neighbor hopping pathways.