On the arrangement of chromophores in light harvesting complexes: chance versus design
We used a homogeneous computational approach to derive the excitonic Hamiltonian for five light harvesting complexes and compare them in terms of statistical descriptors. We then studied the approximate exciton dynamics for the five complexes introducing a measure, the (averaged and time-dependent) inverse participation ratio, that enables the comparison between very diverse complexes on the same ground. We find that the global dynamics is very similar across the set of systems despite the variety of geometric structure of the complexes. In particular, the dynamics of four out of five light harvesting complexes are barely distinguishable with a small variation from the norm seen only for the Fenna-Matthews-Olson complex. We use the information from the realistic Hamiltonians to build a reduced model system that shows how the global dynamics is ultimately dominated by a single parameter, the degree localization of the excitonic Hamiltonian eigenstates. Considering the physically plausible range of system parameters, the reduced model explains why the dynamics is so similar across most light harvesting complexes regardless of the detailed pattern of the inter-chromophore excitonic coupling.
- This article is part of the themed collection: Quantum effects in complex systems