Classification of Coherent Enhancements of Light-Harvesting Processes

TL;DR

This paper classifies mechanisms by which quantum coherence can enhance light-harvesting efficiency, predicting a new mechanism where coherence reduces recombination by localizing excitons away from dissipation.

Contribution

It provides a comprehensive classification of coherence effects in light-harvesting systems and predicts a novel enhancement mechanism involving eigenstate coherence.

Findings

Enhancements require different bases for coherence and dissipation.

A new mechanism uses eigenstate coherence to localize excitons and reduce recombination.

The classification predicts previously unreported coherence-based efficiency improvements.

Abstract

Several kinds of coherence have recently been shown to affect the performance of light-harvesting systems, in some cases significantly improving their efficiency. Here, we classify the possible mechanisms of coherent efficiency enhancements, based on the types of coherence that can characterise a light-harvesting system and the types of processes these coherences can affect. We show that enhancements are possible only when coherences and dissipative effects are best described in different bases of states. Our classification allows us to predict a previously unreported coherent enhancement mechanism, where coherence between delocalised eigenstates can be used to localise excitons away from dissipation, thus reducing recombination and increasing efficiency.