Superradiance Transition and Nonphotochemical Quenching in Photosynthetic Complexes

We demonstrate numerically that superradiance could play a significant role in light-harvesting complexes, when two escape channels into continuum for the exciton are competing. Our model consists of a network of five interconnected sites (discrete excitonic states). Damaging and charge transfer states are linked to their sinks (independent continuum electron spectra), in which the chemical reactions occur. The superradiance transition in the charge transfer (or in the damaging) channel occurs at particular electron transfer rates from the discrete to the continuum electron spectra and can be characterized by a segregation of the imaginary parts of the eigenvalues of the effective non-Hermitian Hamiltonian. All five excitonic sites interact with their protein environment that is modeled by a random stochastic process. We find the region of parameters in which the superradiance transition into the charge transfer channel takes place. We demonstrate that this superradiance transition has the capability of producing optimal escape into the charge transfer channel.