Explicit Correlated Exciton-Vibrational Dynamics of the FMO Complex

TL;DR

This study investigates the detailed exciton-vibrational dynamics in the FMO complex using an exact quantum approach, revealing how specific vibrational modes influence electronic coherence and population decay.

Contribution

It provides a numerically exact analysis of exciton-vibrational interactions in a 3-site FMO model, highlighting the importance of particular vibrational frequency ranges.

Findings

Vibrational modes between 160 and 300 cm$^{-1}$ cause subpicosecond decay of populations and coherences.

Mean-field vibrational approximations are inadequate for accurately describing the dynamics.

Exact quantum treatment reveals specific vibrational contributions to exciton coherence decay.

Abstract

The coupled exciton-vibrational dynamics of a 3-site FMO model is investigated using the numerically exact multilayer multiconfiguration time-dependent Hartree approach. Thereby the vibrational mode specific coupling to local electronic transitions is adapted from a discretized experimental spectral density. The solution of the resulting time-dependent Schr\"odinger equation including three electronic and 450 vibrational degrees of freedom is analyzed in terms of excitonic populations and coherences. Emphasis is put onto the role of specific ranges of vibrational frequencies. It is observed that modes between 160 and 300 cm$^{-1}$ are responsible for the subpicosecond population and coherence decay. Further, it is found that a mean-field approach with respect to the vibrational degrees of freedom is not applicable.