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 important parameters of environmental interactions including reorganization energy λ, bath frequency cutoff γ, temperature T, and bath spatial correlations. We identify the ratio of kBλT/ℏγg as a single key parameter governing quantum transport efficiency, where g is the average excitonic energy gap.
Highlights
Life on the earth has been solar-powered via the mechanism of photosynthesis for 4 × 109 years.1 Photosynthetic antenna complexes have evolved to harvest the sun’s energy and efficiently transport it to reaction centers where it is stored as biochemical energy
We studied the structural and dynamical design principles of excitonic energy transfer in the
We characterized the energy transfer efficiency (ETE) landscape by three main regions: weal localization, environment-assisted quantum transport, and strong localization, and identified the scalar kB λTγ g as the key parameter to cross between these regions as one hikes over the landscape
Summary
Life on the earth has been solar-powered via the mechanism of photosynthesis for 4 × 109 years. Photosynthetic antenna complexes have evolved to harvest the sun’s energy and efficiently transport it to reaction centers where it is stored as biochemical energy. The positive bath correlations can significantly enhance ETE at the regime of large λ by inducing symmetries in the effective phonon-exciton Hamiltonian protecting the transport against strong dynamical disorder. An appropriate level of environmental fluctuations can wash out the quantum localization effects at the equilibrium state, when they are not too strong to lead to quantum Zeno effect.34 These models, are by construction inadequate to capture the role of quantum interplay of system evolution with non-equilibrium dynamics of bath within realistic non-perturbative and non-Markovian regimes.. We have shown that the second-order time-convolution (TC2) master equation can be used to efficiently estimate ETE in large complex excitonic systems interacting with bosonic environments in the intermediate regimes.. Some complementary materials for FMO complex are presented in Appendices on the FMO structural data and ETE in the presence of an Ohmic bath
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