Energy-scales convergence for optimal and robust quantum transport in photosynthetic complexes

TL;DR

This paper investigates the physical principles behind efficient energy transfer in light-harvesting complexes, revealing a convergence of energy scales that optimize and stabilize quantum transport in the FMO complex.

Contribution

It introduces an efficient method to estimate energy transfer efficiency and identifies a key ratio of parameters that governs optimal quantum transport in photosynthetic complexes.

Findings

FMO complex exhibits optimal and robust energy transfer due to energy scale convergence.

Energy transfer efficiency is stable across various environmental and system parameters.

The ratio λT/γ*g is identified as a critical parameter controlling quantum transport efficiency.

Abstract

Underlying physical principles for the high efficiency of excitation energy transfer in light-harvesting complexes are not fully understood. Notably, the degree of robustness of these systems for transporting energy is not known considering their realistic interactions with vibrational and radiative environments within the surrounding solvent and scaffold proteins. In this work, we employ an efficient technique to estimate energy transfer efficiency of such complex excitonic systems. We observe that the dynamics of the Fenna-Matthews-Olson (FMO) complex leads to optimal and robust energy transport due to a convergence of energy scales among all important internal and external parameters. In particular, we show that the FMO energy transfer efficiency is optimum and stable with respect to the relevant parameters of environmental interactions and Frenkel-exciton Hamiltonian including reorganization energy $\lambda$, bath frequency cutoff $\gamma$, temperature $T$, bath spatial correlations, initial excitations, dissipation rate, trapping rate, disorders, and dipole moments orientations. We identify the ratio of $\lambda T/\gamma\*g$ as a single key parameter governing quantum transport efficiency, where g is the average excitonic energy gap.