Exciton dynamics of molecular aggregate systems composed of triangular lattice units: Structural dependence of exciton-migration and recurrence

The exciton dynamics in molecular aggregate models composed of triangular lattice units have been investigated using the quantum master equation approach including relaxation terms originating in weak exciton-phonon coupling. We observe directed migration and recurrence motion of exciton after the irradiation of a laser field. It is found that the triangular lattice aggregates tend to suppress the decoherence behavior and thus to exhibit more distinguished longer-term exciton recurrence than the similar size dendritic aggregates, although the former show less efficient exciton migration, that is, light-harvesting behavior, than the latter. These dynamical features of exciton in the triangular lattice aggregate models turned out to be characterized by the strong interactions among spatially close-packed monomers through the branching points, originating in the equilateral triangular structure, as well as by the fractal, tournament-like, architecture.