Energy transfer under natural incoherent light: Effects of asymmetry on efficiency

TL;DR

This paper investigates how asymmetry affects energy transfer efficiency in donor-acceptor systems under natural incoherent light, revealing detrimental effects of asymmetry and complex coherence behaviors influencing transfer pathways.

Contribution

It provides a detailed analysis of non-equilibrium coherences and their impact on energy transfer efficiency, highlighting the effects of asymmetry and dephasing mechanisms.

Findings

Asymmetry generally reduces energy transfer efficiency.

A turnover effect in efficiency occurs under weak dimer coupling with site basis dephasing.

The ratio of real to imaginary parts of coherences approaches a constant in steady state.

Abstract

The non-equilibrium stationary coherences that form in donor-acceptor systems are investigated to determine their relationship to the efficiency of energy transfer to a neighboring reaction center. It is found that the effects of asymmetry in the dimer are generally detrimental to the transfer of energy. Four types of systems are examined, arising from combinations of localized trapping, delocalized (Forster) trapping, eigenstate dephasing and site basis dephasing. In the cases of site basis dephasing the interplay between the energy gap of the excited dimer states and the environment is shown to give rise to a turnover effect in the efficiency under weak dimer coupling conditions. Furthermore, the nature of the coherences and associated flux are interpreted in terms of pathway interference effects. In addition, regardless of the cases considered, the ratio of the real part and the imaginary part of the coherences in the energy-eigenbasis tends to a constant value in the steady state limit.