Multiscale photosynthetic exciton transfer

TL;DR

This paper investigates the potential for long-range coherent exciton transfer in disordered chromophore networks, revealing that clustering and reduced decoherence at larger scales could enable efficient energy transfer over extended distances at physiological temperatures.

Contribution

It demonstrates that long-range coherence can be sustained in disordered, clustered chromophore networks, providing insights for bio-inspired energy transfer systems.

Findings

Decoherence decreases at larger scales due to renormalization.

Chromophoric clustering facilitates long-range coherence.

Static disorder limits exciton delocalization at large scales.

Abstract

Photosynthetic light harvesting provides a natural blueprint for bioengineered and biomimetic solar energy and light detection technologies. Recent evidence suggests some individual light harvesting protein complexes (LHCs) and LHC subunits efficiently transfer excitons towards chemical reaction centers (RCs) via an interplay between excitonic quantum coherence, resonant protein vibrations, and thermal decoherence. The role of coherence in vivo is unclear however, where excitons are transferred through multi-LHC/RC aggregates over distances typically large compared with intra-LHC scales. Here we assess the possibility of long-range coherent transfer in a simple chromophore network with disordered site and transfer coupling energies. Through renormalization we find that, surprisingly, decoherence is diminished at larger scales, and long-range coherence is facilitated by chromophoric clustering. Conversely, static disorder in the site energies grows with length scale, forcing localization. Our results suggest sustained coherent exciton transfer may be possible over distances large compared with nearest-neighbour (n-n) chromophore separations, at physiological temperatures, in a clustered network with small static disorder. This may support findings suggesting long-range coherence in algal chloroplasts, and provides a framework for engineering large chromophore or quantum dot high-temperature exciton transfer networks.