Energy transfer in light-harvesting systems:
Influence of non-Markovian environment

(1) MPI for the Physics of Complex Systems, Nöthnitzer Straße 38, Dresden
(2) Department of Chemistry, University of California, Berkeley, CA
(3) Institute for Theoretical Physics, University of Technology Dresden
(4) Department of Chemistry and Chemical Biology, Harvard University Cambridge, MA

The transfer of electronic excitation energy as well as optical properties of complexes of interacting chromophores, e.g. the FMO complex or the LH2 antennae in biological photosynthetic systems, are strongly influenced by an environment. For a proper theoretical description it is essential to include non-Markovian effects resulting from an electron-environment coupling that is a rather structured function of energy leading to a complicated retroaction on the excitation dynamics.

We developed a new approach based on non-Markovian quantum state diffusion [1] where it is possible to efficiently calculate energy transfer and optical spectra in a non-perturbative way solving a time-dependent stochastic Schrödinger equation for an electronic wavefunction. We recover the reduced density operator by averaging over many realizations of the stochastic noise.
Within this method, it is possible to capture the whole range from coherent dynamics to incoherent diffusion and to investigate situations where environment-assisted transfer occurs.

Using that approach we described the energy transfer dynamics in one FMO subunit as well as in the full FMO trimer. [2,3]

[1] J. Roden, A. Eisfeld, W. Wolff, W. T. Strunz (2009) Phys. Rev. Lett., 103, 058301
[2] G. Ritschel, J. Roden, W. T. Strunz, A. Eisfeld arXiv:1106.5259v1
[3] G. Ritschel, J. Roden, W. T. Strunz, A. Aspuru-Guzik, A. Eisfeld arXiv:1108.3452v2