СЕМИНАР: др Вељко Јанковић

У оквиру семинара Центра за изучавање комплексних система Института за физику у Београду, у четвртак, 17. децембра 2020. године у 14 часова путем Zoom платформе, др Вељко Јанковић (Лабораторија за примену рачунара у науци, Институт за физику у Београду) одржаће предавање:

Relevance of incoherent light-induced coherences for photosynthetic energy transfer


The interpretation of oscillatory features in experimental signals from photosynthetic pigment-protein complexes excited by laser pulses [1] has been motivating vigorous interest in quantum effects in photosynthetic energy transfer (ET) [2]. However, electronic dynamics triggered by natural light, which is stationary and incoherent, is generally substantially different from the one observed in pulsed laser experiments. It has been suggested that the physically correct picture of photosynthetic ET should be in terms of a nonequilibrium steady state (NESS) [3], which is formed when a photosynthetic complex is continuously photoexcited and continuously delivers the excitation energy to the reaction center (RC), in which charge separation takes place.

In this talk we will consider ET in a molecular aggregate that is driven by weak incoherent radiation and coupled to its immediate environment and the RC. We will combine a second-order treatment of the photoexcitation with an exact treatment of the excitation-environment coupling and formulate the hierarchy of equations of motion (HEOM) that explicitly takes into account the photoexcitation process [4]. We will develop an efficient numerical scheme that respects the continuity equation for the excitation fluxes to compute the NESS of the aggregate [5]. The NESS is most conveniently described in the so-called preferred basis, in which the excitonic density matrix is diagonal. Having established the proper NESS description, we will critically reassess the involvement of stationary coherences in the photosynthetic ET and claims that stationary coherences may enhance the ET efficiency. Focusing on a model photosynthetic dimer, we will also examine the properties of the NESS and establish a general relationship between NESS picture and time-dependent description of an incoherently driven, but unloaded system.

[1] G. S. Engel et al., Nature 446, 782 (2007).
[2] J. Cao et al., Sci. Adv. 6, eaaz4888 (2020).
[3] P. Brumer, J. Phys. Chem. Lett. 9, 2946 (2018).
[4] V. Janković and T. Mančal, arXiv: 2001.07180 (2020).
[5] V. Janković and T. Mančal, arXiv: 2008.13395 (2020).

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Meeting ID: 899 2935 0836
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