# Does electronic coherence enhance anticorrelated pigment vibrations under realistic conditions?

## TL;DR

This study investigates whether electronic coherence and anticorrelated vibrational modes are enhanced by vibronic coupling in a molecular dimer under realistic conditions, finding no such enhancement occurs.

## Contribution

It provides a detailed analysis showing that vibronic coupling does not extend electronic coherence or amplify anticorrelated vibrational modes at ambient conditions.

## Key findings

- Electronic coherence is not extended by vibronic coupling.
- Anticorrelated vibrational modes are not enhanced by vibronic coupling.
- Long-lived oscillations are due to ground-state vibrational coherence.

## Abstract

The light-harvesting efficiency of a photoactive molecular complex is largely determined by the properties of its electronic quantum states. Those, in turn, are influenced by molecular vibrational states of the nuclear degrees of freedom. Here, we reexamine two recently formulated concepts that a coherent vibronic coupling between molecular states would either extend the electronic coherence lifetime or enhance the amplitude of the anticorrelated vibrational mode at longer times. For this, we study a vibronically coupled dimer and calculate the nonlinear two-dimensional (2D) electronic spectra which directly reveal electronic coherence. The timescale of electronic coherence is initially extracted by measuring the anti-diagonal bandwidth of the central peak in the 2D spectrum at zero waiting time. Based on the residual analysis, we identify small-amplitude long-lived oscillations in the cross-peaks, which, however, are solely due to groundstate vibrational coherence, regardless of having resonant or off-resonant conditions. Our studies neither show an enhancement of the electronic quantum coherence nor an enhancement of the anticorrelated vibrational mode by the vibronic coupling under ambient conditions.