Quantum effects in energy and charge transfer in an artificial photosynthetic complex

TL;DR

This study models quantum dynamics in an artificial photosynthetic complex, revealing efficient energy transfer, rapid charge separation, and observable quantum beatings, highlighting quantum effects in bio-inspired energy systems.

Contribution

The paper derives exact non-Markovian equations for quantum dynamics in an artificial photosynthetic complex, enabling analysis of strong system-bath interactions and quantum effects.

Findings

Energy efficiently transferred to reaction center within a few picoseconds.

Quantum beatings observed with decoherence times of ~100 fs.

Pronounced quantum oscillations of charge with ~20 fs decoherence at low temperatures.

Abstract

We investigate the quantum dynamics of energy and charge transfer in a wheel-shaped artificial photosynthetic antenna-reaction center complex.This complex consists of six light-harvesting chromophores and an electron-acceptor fullerene. To describe quantum effects on a femtosecond time scale, we derive the set of exact non-Markovian equations for the Heisenberg operators of this photosynthetic complex in contact with a Gaussian heat bath. With these equations we can analyze the regime of strong system-bath interactions, where reorganization energies are of the order of the intersite exciton couplings. We show that the energy of the initially-excited antenna chromophores is efficiently funneled to the porphyrin-fullerene reaction center, where a charge-separated state is set up in a few picoseconds, with a quantum yield of the order of 95%. In the single-exciton regime, with one antenna chromophore being initially excited, we observe quantum beatings of energy between two resonant antenna chromophores with a decoherence time of $\sim$ 100 fs. We also analyze the double-exciton regime, when two porphyrin molecules involved in the reaction center are initially excited. In this regime we obtain pronounced quantum oscillations of the charge on the fullerene molecule with a decoherence time of about 20 fs (at liquid nitrogen temperatures). These results show a way to directly detect quantum effects in artificial photosynthetic systems.