Anomalous exciton localization in systems with heavy-tailed disorder

The optical and excitation transport properties of a wide variety of systems, such as molecular aggregates, photosynthetic complexes and organic photovoltaics, are determined by the collective properties of the relevant excitations, which are strongly influenced by interactions with their environment. In modeling the behavior of these collective excitations (excitons) in a disordered environment, one conventionally often considers model parameters as stochastic quantities with Gaussian distributions. However, we have shown that the limitation to Gaussian distributions is not necessarily the best choice, and that a generalization to the wider class of Lévy distributions leads to qualitatively different collective optical properties.

In this talk, I will discuss how the details of the considered disorder distributions influence the localization properties of excitons in supramolecular systems, and in turn their optical and energy transport properties. First, I will discuss how a generalization to Lévy disorder distributions affects the localization behavior and the absorption properties of the optically relevant exciton states. It will be shown that such a generalization leads to novel effects such as exchange broadening and an anomalous exciton localization. Moreover, I will show that Lévy distributions follow quite naturally from a simple microscopic model. In addition, the modified localization properties are shown to cause a qualitative change in exciton dynamics, leading to subdiffusive (i.e. less mobile than diffusive) behavior of the exciton transport.