Effects of electronic-vibrational resonance on the absorption and two-dimensional rephasing spectra of the Fenna–Matthews–Olson complex

Abstract

The absorption and two-dimensional rephasing spectra of the Fenna–Matthews–Olson (FMO) complex at 77 K have been simulated using the hierarchical equations of motion method. Three cases of vibrational coupling have been studied in the FMO complex model. In the first case, no specific vibrational mode is coupled. In the second and third cases, low-energy and high-energy electronic-vibrational resonance dimers are considered in the model, respectively. It has been observed that the vibrational mode significantly weakens the intensity of the absorption peak of resonant high-energy electronic transitions. We have also confirmed that long-lived quantum beatings originate from vibration, while short-lived electronic coherence still persists. Furthermore, although the electronic resonance mode speeds up the rephasing dynamics, it is not directly proportional to the coupling strength. The low-energy electronic-vibrational resonance dimer exhibits a greater speed-up of rephasing dynamics.