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National Repository of Grey Literature 2 records found  Search took 0.00 seconds. 
Influence of intra-molecular vibrational modes on excitation energy transfer in molecular aggregates
 Herman, Daniel ; Mančal, Tomáš (advisor) ; Zamastil, Jaroslav (referee)
The energy transfer in molecular aggregates is generally hard to describe in a simple yet effective manner. There is often a trade-off between the accuracy of simulated results and the level of understanding of the underlying physics. To understand the evolution of a system with electronic degrees of freedom, understanding the influence of the system's evolution on the evolution of the bath is also required. To obtain an insight into the bath evolution, we introduce an exact factorization of the density matrix elements representing an entangled state of the bath and the system. We leverage this factorization to derive iterative quantum master equations. Iterative treatment of bath evolution is then used to derive corrected memory kernel with correlation functions in a local basis with the assumption of linear harmonic oscillators as modes of the bath. This approach attempts to improve existing perturbative master equations in a regime of weak interaction between the system and the bath. To judge the improvement achieved, we apply the theory to systems with the finite bath of small size. 1
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Electron-phonon Coupling in Finite Multi-chromophoric Systems
 Herman, Daniel ; Mančal, Tomáš (advisor) ; Profant, Václav (referee)
Quantum systems in nature interact with other quantum systems, and these are examples of open quantum systems. In this work, we provide an introduction to the theory of open quantum system with a particular focus on the dynamics of molecular systems embedded in the protein environment, such as those found in photosynthetic antennas. We devote some time to the techniques of constructing equations of motion for the dynamics of a selected quantum system under the interaction with the bath, where we restrict ourselves to a finite number of degrees of freedom. We compare the exact calculation of the whole finite system with the results of approximate equations derived from an ansatz for the time evolution for the degrees of freedom of the bath part. We also reformulate the exact equations into a time non-local master equation using projection operator techniques, and we study the quality of results obtained with the modified quantum master equation. The time evolution of studied systems is also compared to the time evolution obtained by Schrödiger and Liouville-von Neumann equations. 1
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See also: similar author names
7 Herman, David
2 Herman, Dominik
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