Coherent and Incoherent Control in Material Systems

通过该奖项，化学部门的化学理论、模型和计算方法项目正在支持西北大学的Tamar Seideman博士开发和应用新的理论和计算方法来控制纳米级器件的特性，从而增强其功能。这项研究的重点是分子或纳米电子学。在一项研究中，塞德曼和他的同事介绍了一种通过光而不是电压驱动电流通过结的方法，这种方法可以避免先前经历的光引起的损伤。第二个研究方向引入了一种非常需要的理解传输结的方法，该方法利用光谱学的灵敏度来准确表征分子尺度电子学的结构和化学组成。第三，更雄心勃勃的研究，引入了一个新的控制概念，即量子最优环境工程。在这里，Seideman小组的目标是发展一种理论和一种数值方法来优化使用比激光更便宜的试剂的反应结果。计划应用于操纵电荷转移反应，以提高太阳能电池的效率。这些研究中的第一个是建立在之前nsf支持的研究的成功基础上的，Seideman介绍了一种通过半导体为基础的分子尺度电子学来相干控制传输的方法，作为绕过传统金属为基础的分子尺度电子学相关困难的途径，这些困难在之前的实验文献中已经提到过。目前的研究超越了她早期的完全解析解决方案，该解决方案仅限于1点和2点桥梁情况以及马尔可夫动力学，通过开发一种数值方法并将其应用于探索记忆效应和多点动力学。第二个研究方向是探索电流诱导拉曼光谱，利用拉曼光谱的化学灵敏度来准确表征分子尺度结的结构和化学组成，以及它们所表现出的输运和电流驱动动力学。另一个正在开发的理论是，在统一的方法下，首先确定一个简单的吸附双原子分子的输运、电流驱动动力学和拉曼光谱，然后是罗丹明6G/银的降维模型。第三个项目依赖于最近的研究，该研究表明，环境可以配置为以高精度引导量子系统进入纠缠量子态，并以超快的时间精度快速打开和关闭多个衰减通道。此外，这些环境控制可能允许将系统引导到希尔伯特空间的区域，这些区域是连贯控制无法达到的。应用环境工程概念，通过中间高桥态有效地将光激发给体态转化为自由电荷载流子，并通过有效的单重态到三重态自旋态转换来抑制极化子态中电荷重组引起的损失。

With this award, the Chemical Theory, Models and Computational Method program in the Chemistry division is supporting Dr. Tamar Seideman of Northwestern University to develop and apply new theoretical and computational approaches for controlling the properties of nanoscale devices and thus enhance their functionalities. This research is focused on molecular or nanoscale electronics. In one study, Seideman and coworkers introduce an approach to drive current through junctions with light, rather than with voltage, in a way that circumvents the earlier experienced light-induced damage. A second research direction introduces a much needed approach to understanding transport junctions, which enlists the sensitivity of spectroscopy to accurately characterize the structure and chemical composition of molecular-scale electronics. A third, more ambitious study, introduces a new control concept, namely, quantum optimal environment engineering. Here the Seideman group aims to develop a theory and a numerical method to optimize reaction outcomes using reagents that are less costly than lasers. An application is planned to manipulate charge transfer reactions with a view to enhancing the efficiency of solar cells. The first of these studies builds on the success of previous NSF-supported research, where Seideman introduced an approach to coherent control of transport via semiconductor-based molecular-scale electronics as a route to circumventing the difficulties associated with conventional, metal-based molecular-scale electronics, which were noted in the previous experimental literature. The current research goes beyond her earlier, fully analytical solution, which was restricted to the 1- and 2-site bridge cases and to Markovian dynamics, by developing a numerical method and applying it to explore memory effects and multiple-site dynamics. The second research direction explores current-induced Raman spectroscopy as a route to enlisting the chemical sensitivity of Raman spectra to accurately characterize the structure and chemical composition of molecular-scale junctions, and the transport and current-driven dynamics they exhibit. Also under development is a theory to determine, within a uniform approach, the transport, current-driven dynamics and Raman spectra first for a simple adsorbed diatomic molecule and next for a reduced dimensionality model of rhodamine 6G/silver. The third project relies on recent research that shows that the environment can be configured to steer the quantum system into entangled quantum states with high accuracy, as well as to rapidly switch on and off multiple decay channels with ultrafast time precision. Moreover, these environmental controls can potentially allow steering the system into regions of the Hilbert space that are out of reach of coherent control. Environmental engineering concepts are applied to efficiently transform optically excited donor states into free charge carriers via intermediate higher-lying bridge states, and to suppress the losses caused by charge recombination in the polaron states via effective singlet-to-triplet spin state conversion..