A photosynthetic system with electronically excited pigments together with protein environment that interferes in the excitation energy transfer is a typical case where quantum-classical approaches can be usefully adopted. The Poisson bracket mapping equation (PBME) provides such solutions by combining a quantum subsystem with classically described bath degrees of freedom. Here, we report our PBME simulation results of a model of the algae pigment-protein system cryptophyte phycocyanin 645 complex and compare the evolution of its density matrix at a physiological temperature. We also compare them to the results from the hierarchical equation of motion method, which is known to give more accurate solutions. The two methods produced similar behavior including coherence at short time scale even though a trapping phenomenon on an intermediate energy state appeared quite differently. More significant discrepancy was that PBME could not reproduce the excited state populations in the long time limit, likely from the limitation related to the issue of the zero-point energy leak. We will also discuss what approaches can be taken to improve on the approximation.

Environmental effect on excited energy transfer in photosynthetic light harvesting complex: Comparing Poisson bracket mapping equation and reduced hierarchical equation of motion

249th National Meeting (2015)

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