Phenomenology of Correlated Electron Systems

[00:08 . 39]科学中一些最深奥的问题与电子的运动有关，电子是电的载体。它们的行为受量子多体理论的支配，量子多体理论的定律往往会导致奇怪而美丽的结果。对这些粒子的理解，以及由此产生的对它们的控制，奠定了从化学工程到计算机等广泛技术的基础。对于固态物理学来说，一个特别困难的挑战是理解电子群在特殊情况下的行为：当它们由于相互作用而集体行动时。这是一个比孤立电子的个体行为深刻得多的问题。后者的理解相对发达，并形成了今天的电气技术的基础。对集体行为的理解将对未来的技术非常重要。本课题的研究从实验分析和基础计算两个不同的方向来解决这个问题。为了理解电子的集体或相关行为，我们必须有完善的工具来收集有关它们的信息。其中一个非常重要的工具是光电效应，它通过观察光线照射金属时从金属中出现的电子来探测电子行为。为了让这个实验给出关于金属的准确信息，我们必须了解电子在被检测到之前减速和损失能量的各种方式。这种能量损失的计算以及由此产生的实验特征是研究的一个重点。第二个重点是计算被称为量子点的非常小的结构中的电子能量。随着芯片和存储元件的不断小型化，这些结构在未来的计算机技术中肯定是重要的。目前的理论并不能很好地解释电子在这些结构中的运动。它们的能量水平令人费解：我们甚至缺乏一个粗略的统计描述。我们将使用一种基于生物学思想的算法，即所谓的遗传算法，来计算这些水平。这将是第一次这样的想法被专门应用于这些粒子的量子性质。电子集体行为的一个非常重要的例子是超导性：电子作为一个群体携带电流的能力。近年来，这些重要的新型材料被发现，它们的性质是新颖的，在许多情况下，人们对它们知之甚少。这一领域的理论研究是长期努力的延续，重点是理解大量的实验和构建结合超导和磁性现象的模型

0081039JoyntSome of the deepest problems in science have to do with the motion of electrons, the carriers of electricity. Their behavior is governed by quantum many-body theory, whose laws often lead to strange and beautiful consequences. The understanding of these particles, and the resulting control that we have over them, underlies a wide range of technology from chemical engineering to computers.A particularly difficult challenge for solid-state physics is to understand the behavior of groups of electrons under special circumstances: when they act collectively because of their mutual interactions. This is a much deeper problem than the individual behavior of isolated electrons. The understanding of the latter is relatively well developed and forms the basis for today's electrical technology. The understanding of collective behavior will be important for the technology of tomorrow. The research in thi sgrant attacks this problem from two different directions: experimental analysis and fundamental calculations.In order to understand collective, or correlated, behavior of electrons, we must have well-developed tools for gathering information about them. One very important such tool is the photoelectric effect, which probes electron behavior by looking at the electrons that emerge from a metal when light is shown on it. In order for this experiment to give accurate information about the metal, we must understand the various ways that the electron can slow down and lose energy before it is detected. Calculations of thi senergy loss, and the resulting experimental signatures, i sone focus of the research.A second focus is to calculate the energies of electrons in very small structures called quantum dots. These structures are sure to be important in future computer technology, as miniaturization of chips and memory elements continues. Current theory does not furnish a good account of the motion of electrons in these structures. Their energy levels are puzzling: we even lack a rough, statistical description. We will use an algorithm based on biological ideas, the so-called gentic algorithm, to calculate these levels. This will be the first time such ideas have been applied specifically to the quantum nature of these particles.One very important example of collective behavior of electrons is superconductivity: the ability of electrons to carry electrical current as a group. Important new classes of these materials have been discovered in recent years, and their properties are novel and, in many cases, poorly understood. The theoretical research in this area, a continuation of a long-standing effort, focuses on understanding numerous experiments and constructing models that combine the phenomena of superconductivity and magnetism.***