Reduced density matrix hybrid approach: Application to electronic energy transfer

TL;DR

This paper introduces a hybrid method combining Ehrenfest dynamics with a quantum treatment of fast environmental modes to accurately model electronic energy transfer in complex biological systems.

Contribution

It develops a reduced density matrix hybrid framework that improves the accuracy of energy transfer simulations in regimes where system and environment energy scales are comparable.

Findings

Accurately models energy transfer in photosynthetic complexes.

Demonstrates effectiveness on a model dimer and Fenna-Matthews-Olson complex.

Shows environmental preparation influences energy transfer dynamics.

Abstract

Electronic energy transfer in the condensed phase, such as that occurring in photosynthetic complexes, frequently occurs in regimes where the energy scales of the system and environment are similar. This situation provides a challenge to theoretical investigation since most approaches are accurate only when a certain energetic parameter is small compared to others in the problem. Here we show that in these difficult regimes, the Ehrenfest approach provides a good starting point for a dynamical description of the energy transfer process due to its ability to accurately treat coupling to slow environmental modes. To further improve on the accuracy of the Ehrenfest approach, we use our reduced density matrix hybrid framework to treat the faster environmental modes quantum mechanically, at the level of a perturbative master equation. This combined approach is shown to provide an efficient and quantitative description of electronic energy transfer in a model dimer and the Fenna-Matthews-Olson complex and is used to investigate the effect of environmental preparation on the resulting dynamics.