Coherent transport and energy flow patterns in photosynthesis under incoherent excitation.
Long-lived coherences have been observed in photosynthetic complexes after laser excitation, inspiring new theories regarding the extreme quantum efficiency of photosynthetic energy transfer. Whether coherent (ballistic) transport occurs in nature and whether it improves photosynthetic efficiency remain topics of debate. Here, we use a nonequilibrium Green's function analysis to model exciton transport after excitation from an incoherent source (as opposed to coherent laser excitation). We find that even with an incoherent source, the rate of environmental dephasing strongly affects exciton transport efficiency, suggesting that the relationship between dephasing and efficiency is not an artifact of coherent excitation. The Green's function analysis provides a clear view of both the pattern of excitonic fluxes among chromophores and the multidirectionality of energy transfer that is a feature of coherent transport. We see that even in the presence of an incoherent source, transport occurs by qualitatively different mechanisms as dephasing increases. Our approach can be generalized to complex synthetic systems and may provide a new tool for optimizing synthetic light harvesting materials.
Department of Chemistry, The James Franck Institute, and the Institute for Biophysical Dynamics, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.
Kenley M
KM
Pelzer
Tankut
T
Can
Stephen K
SK
Gray
Dirk K
DK
Morr
Gregory S
GS
Engel
D000465:Algorithms; D001426:Bacterial Proteins / Q000737:chemistry*; D019414:Chlorobi; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D008956:Models, Chemical; D055668:Photochemical Processes; D010788:Photosynthesis; D017433:Protein Structure, Secondary
D001426:Bacterial Proteins; C086320:FMO bacteriochlorophyll protein, Bacteria; D045342:Light-Harvesting Protein Complexes