| Abstract [eng] |
Non-Markovian Transport of Excitations in Molecular Aggregates Exciton relaxation and transport in condensed matter is a complex problem combining principles of quantum mechanics, statistics and thermodynamics. The main characteristics that enters into exciton relaxation dynamics is thermal phonon induced exciton Hamiltonian fluctuation spectral density or its Fourier transform - fluctuation correlation function. Exciton relaxation and transport in photosynthetic complexes is important, as it can be used for effective light harvesting and conversion mechanisms in synthetic systems. One of the problems to consider when we model photosynthetic complex dynamics is the importance of non-Markovian effects, which defines if there is memory in relaxation process. When modeling photosynthetic molecular aggregate dynamics there is often assumed that if correlation function decays faster that the dynamics, then non-Markovian effects can be neglected. But non-Markovian effects may be important for molecular excitation transfer in molecular complexes. The fluctuation spectral density is indirect experimentally observed quantity. It defines exciton transfer and line shape for absorption, fluorescence spectra. From experiments spectral densities varies with different photosynthetic complexes. Experimentally spectral density can be obtained using delta fluorescence line narrowing at low temperature. For theoretical modeling of dynamics and spectra spectral density is often used as defined mathematical expressions, which only is suitable for use in certain frequency range or deviates significantly from experimentally obtained spectral density. In this work we study a cylindrical aggregate dynamics including non-Markovian effects using different types of spectral density functions to define fluctuation correlation functions. We obtain that at low and high reorganization energy fractional model gives largest influence of coherences on population dynamics and by increasing reorganization energy the coherence influence increases. For all cases we get that coherences are small and we can use secular approximation. From absorption calculations follows that TC2 model gives non-physical peak splitting in absorption spectrum. |
