Dynamics of Localized Photoexcitations in Condensed Matter Systems

本研究的重点是局域电子态的动力学，它在决定许多电子材料的性质方面起着重要的作用，并且可以显著地改变它们的光学特性和它们的输运性质。这些研究是在可以系统地调节关键物理相互作用--电子-电子和电子-声子相互作用--的材料中进行的。对这些模型体系的研究，包括准一维无机金属络合物和有机金属聚合物，都是利用对电子动力学和振动动力学都敏感的飞秒激光光谱技术完成的。具体问题包括：(1)初始光激发态形成的动力学，(2)激发的电子和振动相干性质，(3)光致缺陷的时间演化，以及(4)电子激发的输运性质。在这项工作中开发和使用的概念和实验方法将适用于广泛的其他光学和电子材料。研究中使用的方法包括研究振动动力学的飞秒振动脉冲激发技术，研究电子相干性质的光子回波测量，以及研究载流子过程和振动动力学的光泵/太赫兹探测技术。研究生培养是这项工作不可或缺的一部分。参与研究的学生将获得使用最先进技术的研究方法和实验技术方面的专业知识，为他们在学术界、工业或政府的一系列职业生涯提供极好的准备。这项研究侧重于局域电子态的动力学，它在决定许多电子材料的性质方面起着重要作用，它可以显著改变它们的光学特性和它们的传输特性。与电子激发局部化有关的问题在纳米级和分子基材料中可能变得特别重要，其中电子激发的大小可以与材料的长度尺度相媲美。这些研究是在可以系统地调整关键物理相互作用的材料中进行的。对这些模型体系的研究，包括准一维无机金属络合物和有机金属聚合物，都是使用最先进的飞秒激光光谱技术完成的，这些技术对电子动力学和振动动力学都很敏感。在这项工作中开发和使用的概念和实验方法将适用于广泛的其他光学和电子材料。基于分子和纳米尺度的电子材料的研究有可能在未来对新技术的发展产生重大影响，以获得广泛的应用，这项工作将有助于理解对未来技术发展至关重要的关键基本物理过程。研究生培养是这项工作不可或缺的一部分。参与研究的学生将获得使用最先进技术的研究方法和实验技术方面的专业知识，为他们在学术界、行业或政府的一系列职业生涯提供良好的准备。

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.