Role of Coherence in Excitation Transfer Efficiency to the Reaction Center in Photosynthetic Bacteria Chlorobium Tepidum

TL;DR

This study explores how quantum coherence influences excitation transfer efficiency in the photosynthetic bacteria Chlorobium Tepidum, revealing that coherence enhances transfer by preventing back transfer and improving overall efficiency.

Contribution

It models the FMO complex with an explicit reaction center and demonstrates the role of coherence in optimizing excitation transfer efficiency using a non-Markovian approach.

Findings

Pure initial states increase trapping at the reaction center.

Coherence blocks back transfer of excitation.

Coherence improves overall transfer efficiency.

Abstract

We investigate the effect of coherence to the excitation transfer efficiency (ETE) in photosynthetic bacteria Chlorobium Tepidum. We have modeled the monomer of Fenna-Matthews-Olson (FMO) complex as consisting of eight bacteriochlorophyll-a sites, while explicitly consider reaction center core complex (RCC) as an additional site. With the use of realistic bath spectrum and several dominant vibronic modes in the non-Markovian master equation, in an effective 9-site model, we have compared the ETE for an initial pure state and an initial mixed state. We observe that the initial pure state relaxes efficiently to increase the trapping at the RCC. We further illustrate that the coherence play a competitive role to block the back transfer of excitation from RCC pigment to FMO complex and hence to maximize the ETE.