Effect of complex inter-site couplings on the excitation energy transfer in the FMO complex

Abstract

It is believed that the quantum coherence itself cannot explain the very high excitation energy transfer (EET) efficiency in the Fenna-Matthews-Olson (FMO) complex. In this paper, we show that this is not the case if the inter-site couplings take complex values. By phenomenologically introducing phases into the inter-site couplings, we obtain the EET efficiency as high as 0.8972 in contrast to 0.6781 with real inter-site couplings. Dependence of the excitation energy transfer efficiency on the initial states is elaborated. Effects of fluctuations in the site energies and inter-site couplings are also examined.

Proposal for probing energy transfer pathway by single-molecule pump-dump experiment

“…23 Nevertheless, these previous studies did not come to an agreement on whether the energy flow in FMO complex passes through site 8 or not. On the other hand, various approaches have been put forward to optimize the energy transfer in the eight-BChls FMO, e.g., by introducing phases in inter-site couplings, 24 and by tuning temperature of the baseplate. 25 At this stage, two questions naturally come to our mind, when we consider designing artificial light-harvesting: 26 whether is it necessary to include an additional BChl in artificial light-harvesting device if the efficiency is not essentially affected by its presence?…”