Superradiance Transition in Photosynthetic Light-Harvesting Complexes

TL;DR

This study reveals that maximal energy transfer efficiency in photosynthetic complexes occurs near the superradiance transition, driven by the coupling to the reaction center, even without thermal effects, aligning with experimental observations.

Contribution

The paper introduces a non-Hermitian Hamiltonian approach to identify the superradiance transition as optimal for energy transfer in light-harvesting complexes.

Findings

Maximal efficiency occurs near the superradiance transition.

The sink's presence is crucial for energy transfer, independent of thermal baths.

Optimal reaction center distance aligns with the superradiance transition.

Abstract

We investigate the role of long-lasting quantum coherence in the efficiency of energy transport at room temperature in Fenna-Matthews-Olson photosynthetic complexes. The excitation energy transfer due to the coupling of the light harvesting complex to the reaction center ("sink") is analyzed using an effective non-Hermitian Hamiltonian. We show that, as the coupling to the reaction center is varied, maximal efficiency in energy transport is achieved in the vicinity of the superradiance transition, characterized by a segregation of the imaginary parts of the eigenvalues of the effective non-Hermitian Hamiltonian. Our results demonstrate that the presence of the sink (which provides a quasi--continuum in the energy spectrum) is the dominant effect in the energy transfer which takes place even in absence of a thermal bath. This approach allows one to study the effects of finite temperature and the effects of any coupling scheme to the reaction center. Moreover, taking into account a realistic electric dipole interaction, we show that the optimal distance from the reaction center to the Fenna-Matthews-Olson system occurs at the superradiance transition, and we show that this is consistent with available experimental data.