Vibronic speed-up of the excitation energy transfer in the Fenna-Matthews-Olson complex

TL;DR

This study demonstrates that underdamped vibrational modes in the Fenna-Matthews-Olson complex enhance excitation energy transfer efficiency by up to 30%, through vibrational and electronic coherence effects.

Contribution

It provides numerically exact quantum dynamical results showing how underdamped vibrations accelerate energy transfer in a biological complex.

Findings

Vibrational coherence oscillations observed at 180 cm$^{-1}$.

Prolonged electronic coherence between excitation sites.

Energy transfer speed increased by up to 30% due to vibrations.

Abstract

We show that the efficient excitation energy transfer in the Fenna-Matthews-Olson molecular aggregate under realistic physiological conditions is fueled by underdamped vibrations of the embedding proteins. For this, we present numerically exact results for the quantum dynamics of the excitons in the presence of nonadiabatic vibrational states in the Fenna-Matthews-Olson aggregate employing a environmental fluctuation spectral function derived from experiments. Assuming the prominent 180 cm$^{-1}$ vibrational mode to be underdamped, we observe, on the one hand, besides vibrational coherent oscillations between different excitation levels of the vibration also prolonged electronic coherent oscillations between the initially excited site and its neighbours. On the other hand, however, the underdamped vibrations provide additional channels for the excitation energy transfer and by this increase the transfer speed by up to $30\%$ .