Electron-LO-Phonon Quantum Kinetics in Wide-Gap II-VI Nanostructures with Strong Confinement

本研究研究了II-VI量子阱和量子线中激子与纵向光学声子的相干耦合。利用超短的亚20飞秒脉冲，在激发时间小于声子振荡周期的条件下，可以探测到这种耦合。除了研究强库仑相互作用和大电子-声子耦合之间的本征性质和干涉现象外，所提出的具有强限制的宽禁带II-VI纳米结构还可以实现激子结合能在LO声子能量以上的独特调谐。因此，可以观察到新的量子动力学效应。这些研究将是对扩展的量子动力学模型的关键检验，并将有助于更好地理解和解释极性准二维和准一维纳米结构中的相干电子-声子散射。研究生将在基础实验技术和尖端技术方面获得经验。这项培训将为他们在学术界、工业界和政府的一系列职业生涯做好准备。本工作旨在研究利用超短飞秒光脉冲研究宽带隙II-VI半导体纳米结构中电子激发与晶格振动之间的相干耦合。在这些实验中，光激发时间比晶格振荡周期短，因此在激发后的早期，电子散射过程可视为干涉现象。这项拟议的研究将揭示新的相干效应，并有助于更好地理解和解释可逆和不可逆电子散射界面上的光激发半导体。这将是对适用于这些纳米结构的扩展理论模型的关键测试。实验结果将对理论研究产生强烈的影响，对信息技术也将具有重要意义。该项目的学生接受超快相干光学和半导体物理方面的严格培训，这为他们在学术界或工业领域的职业生涯做好了准备。

This research investigates coherent coupling between excitons and longitudinal optical (LO)-phonons in II-VI quantum wells and quantum wires. Using ultrashort sub-20-femtosecond pulses, the coupling can be probed under conditions where the excitation time is shorter than the LO-phonon oscillation period. In addition to studying intrinsic properties and interference phenomena between strong Coulomb-interaction and large electron-LO-phonon coupling, the proposed wide-gap II-VI nanostructures with strong confinement also may allow unique tuning of the exciton binding energy above the LO-phonon energy. As a result novel quantum kinetic effects may be observed. The investigations will serve as crucial tests of extended quantum kinetic models and will contribute to an improved understanding and interpretation of the coherent electron-LO-phonon scattering in polar quasi-two and quasi-one dimensional nanostructures. Graduate students will gain experience in fundamental experimental techniques with cutting edge technology. This training will prepare them for a range of careers in academe, industry and government. %%%This work is directed at the study of coherent coupling between electronic excitations and lattice vibrations in wide-band-gap II-VI semiconductor nanostructures utilizing ultrashort femtosecond light pulses. In these experiments the optical excitation time is shorter than the lattice oscillation period so that at early times after excitation electron scattering processes can be treated as interference phenomena. The proposed research will uncover novel coherent effects and contribute to an improved understanding and interpretation of optically excited semiconductors at the interface between reversible and irreversible electron scattering. It will serve as a crucial test of extended theoretical models appropriate for these nanostructures. The experimental results will have a strong impact on theoretical research and will also have importance for information technologies. Students in this program receive rigorous training in ultrafast coherent optics and semiconductor physics, which prepares them for careers in academia or industry.***