Time-resolved role of coherence and delocalization in photosynthetic energy transfer from an extended exciton model

TL;DR

This paper introduces an extended excitonic model for photosynthetic energy transfer that accounts for internal electronic degrees of freedom, revealing how intrachromophoric mixing influences coherence, delocalization, and transfer efficiency over time.

Contribution

It develops a novel extended excitonic network model incorporating intrachromophoric mixing and uses a Lindblad framework to analyze its impact on quantum transport in photosynthesis.

Findings

Intrachromophoric mixing enhances short-time coherence and excitation injection.

Excessive mixing near the trap reduces transfer efficiency.

Spectroscopic signatures correlate internal structure with transport performance.

Abstract

Photosynthetic antenna complexes achieve high quantum efficiency through exciton transport in coupled pigment networks. Conventional Frenkel-exciton models treat each chromophore as a structureless site and neglect internal electronic degrees of freedom that can influence coherence and delocalization. Here we develop an extended excitonic network model that preserves the pigment-pigment coupling topology while introducing tunable intrachromophoric electronic mixing within the single-excitation manifold. Using a Lindblad open-quantum-system framework, we quantify coherence, delocalization, and trapping efficiency across parameter space. We show that intrachromophoric mixing plays a time-dependent role: enhanced mixing on the antenna side promotes short-time coherent delocalization and improves excitation injection, whereas excessive mixing near the trapping site induces persistent delocalization and suppresses transfer efficiency. Simulated two-dimensional electronic spectra reveal enhanced cross peaks and systematic blue shifts, providing spectroscopic signatures of coherence-modulated transport. These results establish a microscopic connection between internal electronic structure and quantum transport performance in excitonic networks.