Development of next generation quantum master equation and generalized master equation approaches

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Seogjoo Jang of CUNY Queens College is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry division to develop new classes of quantum master equation (QME) and generalized master equation (GME) that can bridge molecular level quantum dynamics with larger length and longer time scale dynamics. This is achieved by extending the recently developed polaronic QME (PQME) for a broader regime of parameters, and by developing new coarse-grained QME/GME approaches that can incorporate highly accurate calculation at small length scales into efficient calculation for larger length scales. Another objective of the research is to enhance the reliability and capability of QME/GME approaches. Jang and his coworkers are also developing a new kind of QME that can utilize information on adiabatic electronic states and their derivative couplings directly. Atomistic molecular dynamics simulations are being conducted to examine and modify the conventional form of the exciton-bath Hamiltonian for the photosynthetic light harvesting complex 2 (LH2) of purple bacteria. The methods developed in this research, quantum and generalized master equation approaches, offer natural frameworks for studying exciton and charge carrier dynamics in complex molecular environments, such as natural light harvesting complexes and organic photovoltaic devices. Jang and his research group are taking these approaches to a new level so that they can be applied in a more accurate and realistic manner without relying on simple model systems. The result -- unified and reliable descriptions of quantum relaxation and transport dynamics across a wide range of length/time -- will help elucidate the quantum effects hidden in what appears to be the purely classical behavior of large scale exciton and charge transport dynamics in complex molecular systems.