The effect of site-specific spectral densities on the high-dimensional exciton-vibrational dynamics in the FMO complex

Abstract

The coupled exciton-vibrational dynamics of a three-site model of the FMO complex is investigated using the Multi-layer Multiconfiguration Time-dependent Hartree (ML-MCTDH) approach. Emphasis is put on the effect of the spectral density on the exciton state populations as well as on the vibrational and vibronic non-equilibrium excitations. Models which use either a single or site-specific spectral densities are contrasted to a spectral density adapted from experiment. For the transfer efficiency, the total integrated Huang-Rhys factor is found to be more important than details of the spectral distributions. However, the latter are relevant for the obtained non-equilibrium vibrational and vibronic distributions and thus influence the actual pattern of population relaxation.

Effect of Underdamped Vibration on Excitation Energy Transfer: Direct Comparison between Two Different Partitioning Schemes

“…Recent progresses in modeling techniques ,, have allowed one to extract the intramolecular portion of the spectral density nearly quantitatively, and a few studies have already employed such techniques in simulating quantum dynamics of realistic systems. ,− Including all vibration modes in the subsystem makes the simulation prohibitively burdensome. Therefore, one eventually needs to rely on a method that can appropriately treat intramolecular vibrations in an efficient manner.…”

Semiclassical Path Integral Calculation of Nonlinear Optical Spectroscopy

“…To address these issues, nonperturbative methods that avoid different dynamical approximations have been developed such as the density matrix-based hierarchical equations of motion (HEOM) approach − or the wave function-based multiconfiguration time-dependent Hartree (MCTDH) scheme. , These numerically exact techniques have been extended to compute nonlinear optical responses in recent benchmark studies providing critical tests for more approximate methods. Implementing these exact techniques to compute the nonlinear optical response for larger more realistic models, however, can quickly become prohibitively expensive.…”

High-dimensional exciton-vibrational wave-packet dynamics in the FMO complex. influence of site-specific spectral densities

“…Simulation results are shown for the three-site (! = 1 − 3 ) FMO model as described in [10] using the Heidelberg MCTDH package [11]. Two different SDs will be compared, i.e.…”

“…The Wendling and Coker SDs differ in shape as well as in the integrated Huang-Rhys factor (Wendling: 0.42, Coker: (0.64,0.96,0.58) for sites (1,2,3)). In [10], it was argued that the total Huang-Rhys factor determines the effective decays rates, whereas vibrational and vibronic excitation are sensitive towards the actual shape of the SD. The dependence of the population and also the coherence decay on the SD model is confirmed by Fig.…”