Generic Mechanism of Optimal Energy Transfer Efficiency: A Scaling Theory of the Mean First Passage Time in Exciton Systems

TL;DR

This paper develops a scaling theory for optimal energy transfer efficiency in light-harvesting systems, revealing how environmental damping influences transfer times and efficiency, applicable to various open quantum processes.

Contribution

It introduces a universal scaling law for excitation energy transfer efficiency based on the trapping-free subspace concept, bridging weak and strong damping regimes.

Findings

Efficiency peaks at an optimal damping rate.

Transfer time scales with dephasing rate, changing from linear to square root.

The theory applies broadly to open quantum processes.

Abstract

An asymptotic scaling theory is presented using the conceptual basis of trapping-free subspace (i.e., orthogonal subspace) to establish the generic mechanism of optimal efficiency of excitation energy transfer (EET) in light-harvesting systems. Analogous to Kramers' turnover in classical rate theory, the enhanced efficiency in the weak damping limit and the suppressed efficiency in the strong damping limit define two asymptotic scaling regimes, which are interpolated to predict the functional form of optimal efficiency of the trapping-free subspace. In the presence of static disorder, the scaling law of transfer time with respect to dephasing rate changes from linear to square root, suggesting a weaker dependence on the environment. Though formulated in the context of EET, the analysis and conclusions apply in general to open quantum processes, including electron transfer, fluorescence emission, and heat conduction.