Electronic-vibrational resonance does not alter steady-state transport in natural light-harvesting systems

TL;DR

This study shows that electronic-vibrational resonance does not improve energy transport efficiency in natural light-harvesting systems under steady-state, incoherent light conditions, challenging the significance of quantum coherence observed in spectroscopic experiments.

Contribution

It demonstrates that vibrational-electronic resonance does not affect energy transport in natural steady-state conditions, clarifying the role of quantum coherence in photosynthesis.

Findings

Resonant vibrations do not increase quantum yield.

Vibrational-electronic resonance does not alter energy transport.

Quantum coherence effects are not relevant under natural conditions.

Abstract

Oscillations in time-dependent 2D electronic spectra appear as evidence of quantum coherence in light-harvesting systems related to electronic-vibrational resonant interactions. Nature, however, takes place in a non-equilibrium steady-state, so the relevance of these arguments to the natural process is unclear. Here we examine the role of intramolecular vibrations in the non-equilibrium steady-state of photosynthetic dimers in the natural scenario of incoherent light excitation. It is found that vibrations resonant with the energy difference between exciton states do not increase the quantum yield nor the imaginary part of the intersite coherence that is relevant for transport compared with non-resonant vibrations in the natural non-equilibrium steady state. That is, the vibration-electronic resonance interaction does not alter energy transport under natural incoherent-light excitation conditions.