Electronic Coherence Dephasing in Excitonic Molecular Complexes: Role of Markov and Secular Approximations

Abstract

We compare four different types of equations of motion for reduced density matrix of a system of molecular excitons interacting with thermodynamic bath. All four equations are of second order in the linear system-bath interaction Hamiltonian, with different approximations applied in their derivation. In particular we compare time-nonlocal equations obtained from so-called Nakajima-Zwanzig identity and the time-local equations resulting from the partial ordering prescription of the cummulant expansion. In each of these equations we alternatively apply secular approximation to decouple population and coherence dynamics from each other. We focus on the dynamics of intraband electronic coherences of the excitonic system which can be traced by coherent two-dimensional spectroscopy. We discuss the applicability of the four relaxation theories to simulations of population and coherence dynamics, and identify features of the two-dimensional coherent spectrum that allow us to distinguish time-nonlocal effects.

14 pages, 8 figures

References in corpus (5)

• Environment-Assisted Quantum Walks in Photosynthetic Energy Transfer
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• Environment-Assisted Quantum Transport
• Efficiency of energy transfer in a light-harvesting system under quantum coherence
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• Exact Stochastic Unraveling of an Optical Coherence Dynamics by Cumulant Expansion
• Measuring excitation-energy transfer with a real-time time-dependent density functional theory approach
• Vibrational damping effects on electronic energy relaxation in molecular aggregates