RUI: Spectroscopy of Many-Body Processes in Nanostructures

该项目涉及半导体和金属纳米结构中电子动力学的理论和计算研究。主要的重点将放在理解多体关联和量子限制效应在可以用各种光谱技术测量的光学性质中的作用上。该项目的第一部分将研究强磁场中量子阱中激子的自旋动力学。在磁场中，相互作用的作用增强，多激子态的自旋动力学与库仑关联纠缠。特别令人感兴趣的是由自旋-轨道相互作用促进的亮激子态和暗激子态之间的跃迁的弛豫过程，以及可以用自旋敏感的非线性光学光谱测量的相干自旋动力学。该项目的第二部分与调制掺杂量子阱中多体激发的光谱有关。在许多电子系统中，一个光子的吸收伴随着多体激发的抖动，这导致了光谱中的新特征。特别令人感兴趣的是在吸收单个光子时导致激发一个以上的电子-空穴对的过程。这类过程是碰撞电离的多体模拟，可以有重要的应用，如提高太阳能电池的效率。该项目的第三部分涉及金属纳米结构中的等离子体增强光谱，特别是在金属纳米颗粒阵列附近由分子或半导体点组成的混合系统中。这类系统的光学性质是由金属中点的内部度数和表面集体激发之间的相互作用所决定的。在这里，我们感兴趣的是当分子/点靠近金属纳米结构时产生的量子效应，而不是电磁效应。智力价值拟议的研究将在高电流感兴趣的领域进行，并将有助于解决几个悬而未决的问题。例如，等离子体增强光学特性的准确描述与各种应用相关，例如基于纳米颗粒的传感器和其他生物医学设备。纳米结构中多体过程的理论描述是一项相当具有挑战性的任务，由于存在强烈的量子尺寸效应，因此需要采用非微扰方法。该项目的完成将涉及各种分析和数值方法。结果将与现有的实验数据进行比较，并以出版物和会议报告的形式传播。在整个项目期间，计划让本科生助理积极参与Broader Impact。作为一所历史上以黑人为主的本科院校，杰克逊州立大学主要服务于密西西比州最大城市社区的教育需求。该项目的完成将增加本科生的研究和教育机会，通过让他们接触纳米科学的新概念和方法，主要来自代表不足的群体。非技术摘要：这笔拨款将支持一所本科历史上的黑人大学的理论研究。这项研究将研究金属或半导体纳米结构中的电子性质。特别是，新的光学性质将被研究。学生将参与这项研究。

The proposed project involves theoretical and computational studies of the electron dynamics in semiconductor and metal nanostructures. The prime focus will be placed on the understanding of the role of many-body correlations and quantum confinement effects in the optical properties that can be measured using various spectroscopy techniques.The first part of the project will address spin dynamics of excitons in quantum wells in a strong magnetic field. In a magnetic field, the role of interactions is enhanced and spin dynamics of multi-exciton states is entangled with Coulomb correlations. Of particular interest are the relaxation processes that involve transitions between bright and dark exciton states, facilitated by spin-orbit interactions, and the coherent spin dynamics that can be measured with spin-sensitive nonlinear optical spectroscopy.The second part of the project is related to spectroscopy of many-body excitations in modulation-doped quantum wells. In many-electron systems, the absorption of a photon is accompanied by shakeup of many-body excitations that give rise to novel features in optical spectra. Of particular interest are the processes that result in excitation of more than one electron-hole pair upon absorption of a single photon. Such processes, that are many-body analogues of impact ionization, can have significant applications such as increased efficiency of solar cells.The third part of the project involves plasmon-enhanced spectroscopies in metal nanostructures, in particular, in hybrid systems comprised of a molecule or semiconductor dot in the vicinity of metal nanoparticle arrays. Optical properties of such systems are dominated by interactions between the internal degrees of a dot and surface collective excitations in the metal. Here we are interested in quantum rather than electromagnetic effects that arise when the molecule/dot is in a close proximity to metal nanostructure.Intellectual merit The proposed research will be carried out in areas of high current interest and will contribute to the solution of several outstanding issues. For example, an accurate description of plasmon-enhanced optical characteristics is relevant for a variety of applications, such as nanoparticle-based sensors and other biomedical devices. Theoretical description of many-body processes in nanostructures is a rather challenging task, complicated by strong quantum-size effects, that requires nonperturbative approaches. The completion of the project will involve a variety of analytical and numerical methods. The results will be compared to the available experimental data and disseminated in the form of publications and conference presentations.Broader impact Active participation of undergraduate student assistants is planned throughout entire project duration. Being a historically black predominantly undergraduate institution, Jackson State University primarily serves the educational needs of the Mississippi largest urban community. The completion of the project will enhance research and education opportunities for undergraduate students predominantly from underrepresented groups by exposing them to the new concepts and methods of nanoscience.Non-Technical Abstract: This grant will support theoretical research at an undergraduate historically black university. The research will investigate the properties of electrons in nanoscale structures of metals or semiconductors. In particular, novel optical properties will be studied. Students will participate in the research.