Vibronic enhancement of excitation energy transport: Interplay between local and non-local exciton-phonon interactions

Abstract

It has been reported in recent years that vibronic resonance between vibrational energy of the intramolecular nuclear mode and excitation-energy difference is crucial to enhance excitation energy transport in light harvesting proteins. Here we investigate how vibronic enhancement induced by vibronic resonance is influenced by the details of local and non-local exciton-phonon interactions. We study a heterodimer model with parameters relevant to the light-harvesting proteins with the surrogate Hamiltonian quantum dynamics method in a vibronic basis. In addition, the impact of field-driven excitation on the efficiency of population transfer is compared with the instantaneous excitation, and the effect of multi-mode vibronic coupling is presented in comparison with the coupling to a single effective vibrational mode. We find that vibronic enhancement of site population transfer is strongly suppressed with the increase of non-local exciton-phonon interaction and increasing the number of strongly coupled high-frequency vibrational modes leads to a further decrease in vibronic enhancement. Our results indicate that vibronic enhancement is present but may be much smaller than previously thought and therefore care needs to be taken when interpreting its role in excitation energy transport. Our results also suggest that non-local exciton-phonon coupling, which is related to the fluctuation of the excitonic coupling, may be as important as local exciton-phonon coupling and should be included in any quantum dynamics model.

Importance and Nature of Short-Range Excitonic Interactions in Light Harvesting Complexes and Organic Semiconductors

“…[41][42][43] Any fluctuation of the excitonic couplings due to short range interactions coupled to thermal motion is expected to decrease the coherence and affect the exciton dynamics. 39,44,45 The aim of this paper is to evaluate the excitonic coupling between pairs of chromophores in three different LHCs and in two organic semiconductors (one amorphous and one crystalline), to achieve a broader understanding of the importance of short range interactions valid for most of the problems under current consideration. This large database of structures is used to assess the role of short range interactions with respect to the Coulombic one.…”

Effect of an underdamped vibration with both diagonal and off‐diagonal exciton–phonon interactions on excitation energy transfer

“…For instance, at φ = θ the underdamped vibration does not affect EET dynamics, however, as φ is not equal to θ , the EET is dramatically prompted, especially at φ = θ + π /2. To quantify the promoting effect, we use the time‐averaged population of state ∣ A 〉 over the time window τ : where P A ( t ) is the population in state ∣ A 〉 at time t. Different choices of τ characterize different features of the dynamics. At large τ (much larger than the relaxation time of the exciton), approaches the steady‐state population of state ∣ A 〉.…”

“…One of possible origins is the vibronic coherence from the interactions between the exciton and underdamped vibrations as the vibrational frequencies are resonant with the excitonic energy gap, first proposed by Christensson et al From then on, more and more attentions have been paid on the role of these vibrations on the beating signals as well as the corresponding carrier dynamics. It is now accepted that the underdamped vibrations with resonant frequencies may facilitate the EET, charge separation and singlet fission, which have largely extended the knowledge about resonant vibration‐assisted carrier dynamics. Along this way, various fascinating results have been obtained.…”

Analysis of Photosynthetic Systems and Their Applications with Mathematical and Computational Models

“…A more detailed description of such computational methods and their advancements in this field of research has been elaborated in [56]. The excitonic energy transfer for the biological systems related to the photosynthesis phenomenon, i.e., the biological chromophore and light harvesting complexes, can be evaluated using the path integral dynamics as highlighted in [57][58][59]. Furthermore, the normal mode analysis of the spectral density has been studied using the time-dependent DFT in [60] for computing the spectral densities due to coupling between light harvesting pigments and their corresponding protein.…”