Quantum Kinetics of Laser-Induced Electron Hole Plasmas in Nanowire Arrays

光与物质的相互作用是科学研究的一个基本课题，对许多现代技术至关重要。光电子学的整个研究领域关注的是解释光与电子材料组件的量子相互作用，越来越多地在原子和分子的尺度上。对于许多半导体来说，强烈的激光可以激发电子，然后电子会在身后留下相反的带电阴影，也就是我们所知的“空穴”。这些电子和空穴表现为限制在固体中的等离子体(带电粒子的气体)。即使在今天的超级计算机上，在三维空间中求解描述这种等离子体的复杂方程也是令人望而却步的。然而，量子线的厚度比人的头发还小1000多倍，它们允许我们测试量子等离子体模型，这些电荷仅限于空间中的一维。该项目旨在计算相互作用的量子线中电子-空穴等离子体的演化，以及激发它们的光的演化。其目标是在十亿分之一秒的时间尺度上提高对光产生等离子体的光学和传输性质的知识。这一知识对于理解光与物质的相互作用，以及纳米光电子学、传感和许多国家安全应用方面的进展都很重要。该项目还在为本科生提供参与前沿研究的机会、基于研究成果开发新的大学课程以及使公众能够进行户外活动方面产生了重大的更广泛的影响。在技术方面，该项目的目标是开发改进的计算方法，用于计算量子线中光激电子-空穴等离子体的超快动力学，以及入射到量子线阵列上的超短激光脉冲的散射。计算将把模拟光传输的伪谱时间域(PSTD)技术耦合到量子线中多体等离子体动力学的量子动力学半导体Bloch方程。这个项目通过忽略几个通常用于简化计算的常见假设来提高我们对固体中等离子体动力学的认识，这些假设包括单色激光场、准平衡状态下的电子-空穴分布、介质中空间均匀的电场以及忽略由电子-空穴等离子体空间分布引起的纵场。这些假设是当今涉及强光的光电计算的一个限制因素，特别是在纳米长度和飞秒时间尺度上。该项目将寻求找到量子线等离子体的局域响应与散射光脉冲的时空特征和相位之间的相关性的实验可测量的指标。它还将寻找来自驱动电子-空穴等离子体的电流，以及由于量子线中诱导的、持续时间长的等离子体振荡而产生的局部纵向电磁场之间的可测量相关性。该项目的结果对飞秒电子学和阿秒物理等新兴领域的进步也将是重要的。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The interaction of light with matter is a fundamental topic of scientific research and critical to many modern technologies. The entire research field of optoelectronics is concerned with explaining the quantum interaction of light with electronic material components, increasingly on the scale of atoms and molecules. For many semiconductors, intense laser light can excite electrons, which then leave oppositely-charged shadows behind, known as "holes". These electrons and holes behave as a plasma (a gas of charged particles) confined within the solid. Solving the complicated equations describing such plasmas in three-dimensional space can be prohibitive, even on today's supercomputers. Quantum-wires, however, have a thickness over 1000 times smaller than a human hair, and they allow us to test quantum plasma models on charges that are confined to only one dimension in space. This project aims to calculate the evolution of electron-hole plasmas in interacting quantum wires, as well as the evolution of the light that excites them. The goal is to improve knowledge of optical and transport properties of light-generated plasmas on time-scales of a millionth of a billionth of a second. This knowledge is important for understanding of light-matter interactions, as well as advancements in nano-optoelectronics, sensing, and many national security applications. This project also has significant broader impacts in providing undergraduate students a chance to participate in cutting-edge research, development of new college course curricula based on the research results, and enabling public outreach.On the technical side, the goal of this project is to develop improved calculations of the ultrafast dynamics of photo-excited electron-hole plasmas in quantum wires, as well as the scattering of ultrashort laser pulses incident on a quantum wire array. The computations will couple Pseudo-Spectral Time Domain (PSTD) techniques of modeling light propagation to quantum-kinetic Semiconductor Bloch equations for the many-body plasma dynamics in the quantum wires. This project advances our knowledge of plasma dynamics in solids by dispensing with several common assumptions often used to simplify such calculations; including monochromatic laser fields, electron-hole distributions in quasi-equilibrium, spatially uniform electric fields in the medium, and neglect of longitudinal fields resulting from the spatial electron-hole plasma distribution. These assumptions are a limiting factor on today's optoelectronic calculations involving intense light, particularly on the nanometer length and femtosecond time scales. The project will seek to find experimentally measurable indicators of the correlation between the localized response of quantum-wire plasmas and the spatial-temporal features and phases of the scattered light pulses. It will also look for a measurable correlation between the current from driven electron-hole plasmas, as well as localized longitudinal electromagnetic fields due to induced, long-lasting plasma oscillations in the quantum wires. The results of the project will also be important for advancements in the emerging fields of femtosecond electronics and attosecond physics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.