Multi-Scale Exciton and Electron Transfer in Multi-Level Donor-Acceptor System

TL;DR

This paper provides a theoretical analysis of noise-assisted quantum exciton and electron transfer in complex bio-systems with multi-level acceptors, deriving analytical expressions and demonstrating high efficiency under various conditions.

Contribution

It introduces a comprehensive theoretical model for multi-level donor-acceptor systems, including noise effects, and derives analytical ET rate expressions with insights into multi-scale dynamics.

Findings

Equal occupation of all levels at large times under non-degeneracy.

High ET efficiency approaching 100% with many acceptor levels.

Quantum coherent oscillations influence the acceptor population dynamics.

Abstract

We study theoretically the noise-assisted quantum exciton (electron) transfer (ET) in bio-complexes consisting of a single-level electron donor and an acceptor which has a complicated internal structure, and is modeled by many electron energy levels. Interactions are included between the donor and the acceptor energy levels and with the protein-solvent noisy environment. Different regions of parameters are considered, which characterize (i) the number of the acceptor levels, (ii) the acceptor \band-width", and (iii) the amplitude of noise and its correlation time. Under some conditions, we derive analytical expressions for the ET rate and efficiency. We obtain equal occupation of all levels at large times, independently of the structure of the acceptor band and the noise parameters, but under the condition of non-degeneracy of the acceptor energy levels. We discuss the multi-scale dynamics of the acceptor population, and the accompanying effect of quantum coherent oscillations. We also demonstrate that for large number of levels in the acceptor band, the efficiency of ET can be close to 100%, for both downhill and uphill transitions and for sharp and at redox potentials.