Dynamics of Localized Photoexcitations in Condensed Matter Systems

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This research focuses on the dynamics of localized electronic states, which play an important role in determining the properties of many electronic materials, and which can dramatically alter their optical characteristics as well as their transport properties. The studies are carried out in materials in which the key physical interactions, the electron-electron and electron-phonon interactions, can be systematically tuned. Studies of these model systems, which include both quasi-one-dimensional inorganic metal complexes and organometallic polymers, are accomplished using femtosecond laser spectroscopic techniques that are sensitive to both the electronic and vibrational dynamics. Specific issues addressed include: (1) the dynamics of the formation of the initial photoexcited states, (2) the electronic and vibrational coherence properties of the excitations, (3) the time evolution of the photoinduced defects, and (4) transport properties of the electronic excitations. The conceptual and experimental approaches developed and used in this work will be applicable to a wide range of other optical and electronic materials. Methods employed in the studies include femtosecond vibrationally impulsive excitation techniques to investigate vibrational dynamics, photon echo measurements to investigate electronic coherence properties, and optical pump / THz probe techniques to investigate carrier processes and vibrational dynamics. Graduate student training is an integral part of the work. Students involved in the research will gain expertise in research methods and experimental techniques using state-of-the-art technology, providing them with excellent preparation for a range of careers in academe, industry, or government.This research focuses on the dynamics of localized electronic states, which play an important role in determining the properties of many electronic materials, and which can dramatically alter their optical characteristics as well as their transport properties. Issues related to localization of electronic excitations can become especially important in nanoscale and molecular-based materials, where the size of the electronic excitation can be comparable to the length scale of the material. The studies are carried out in materials in which the key physical interactions can be systematically tuned. Studies of these model systems, which include both quasi-one-dimensional inorganic metal complexes and organometallic polymers, are accomplished using state-of-the-art femtosecond laser spectroscopic techniques that are sensitive to both the electronic and vibrational dynamics. The conceptual and experimental approaches developed and used in this work will be applicable to a wide range of other optical and electronic materials. Research on molecular-based and nanoscale electronic materials has the potential for significant future impact on the development of new technologies for a wide range of applications, and this work will contribute to the understanding of key fundamental physical processes that are important for future technological development. Graduate student training is an integral part of the work. Students involved in the research will gain expertise in research methods and experimental techniques using state-of-the-art technology, providing them with excellent preparation for a range of careers in academe, industry, or government.