How Markovian is exciton dynamics in purple bacteria?

Felix’s work on Markovianity in photosynthetic energy transport has been published: Felix Vaughan, N Linden and F R Manby, J. Chem. Phys. 146, 124113 (2017); http://dx.doi.org/10.1063/1.4978568.

Modelling the interaction between excitons and the surrounding environment is a non-trivial problem. Many interesting insights about excitonic energy transfer have made use of a Markovian or “memoryless” approximation to this interaction. In this paper we assess the applicability of this approximation by employing a new metric of non-Markovianity.

We find that for smooth spectral densities the Markovian approximation works well provided that a precise change to the system Hamiltonian is made, which for the dimer system studied corresponds to an increase in the coupling strength between chromophores. We also find that discrete vibrational modes resonant with the eigenstates of the Hamiltonian induce the greatest degree of non-markovianity. Ultimately we conclude that to model exciton dynamics coupled to realistic spectral densities a Markovian approximation is not suitable.

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