Artificial Atoms

当将电子限制在人造原子中的隧道势垒传输足够多时，引线中电子的运动与孤立区域中电子的运动变得相关。这些关联最戏剧性的表现是近藤效应。最近的实验表明，当孤立区域中有两个未配对的电子而不是一个时，近藤效应的物理性质是根本不同的。随着温度或磁场的降低，关联的发展方式预计将对引线的几何形状敏感。已经对这种情况做出了具体的理论预测，为该项目提出的工作的主要部分就是为了验证这些预测。更广泛地说，用于这些研究的单电子晶体管是研究纳米结构物理的杰出实验室，其中一些最终可能具有重要的技术应用。半导体纳米结构的研究也被证明是年轻物理学家的杰出培训基地。在这一群体中接受教育的以前的学生和博士后助理在小公司、大公司和大学担任过职位。其中很大一部分是妇女和少数民族。计划继续招收本科生、研究生和博士后，特别是女性和少数族裔。纳米科学和工程的进步使人们能够将晶体管制造得如此之小，以至于其中的电子表现为量子力学。理解这种量子行为本质上很有趣，但对于理解如何在纳米尺度上制造有用的电子设备也很重要。当电子被限制在纳米尺度上时，它们可以被认为是人造原子。使人造原子与金属密切接触，会在原子和金属之间产生化学键。这个项目研究了化学键如何依赖于人造原子中的电子数量。因为由人造原子制成的晶体管每增加一个电子就会开启和关闭，所以它们被称为单电子晶体管。除了对技术的兴趣外，单电子晶体管的研究已被证明是年轻物理学家的杰出培训基地。在这一群体中接受教育的以前的学生和博士后助理在小公司、大公司和大学担任过职位。其中很大一部分是女性和少数族裔。计划继续招聘本科生、研究生和博士后，特别是妇女和少数民族。

When the tunnel barriers confining electrons in an artificial atom are transmitting enough, the motion of electrons in the leads becomes correlated with the motion of electrons in the isolated region. The most dramatic manifestation of these correlations is the Kondo effect. Recent experiments have shown that the physics of the Kondo effect is fundamentally different when there are two unpaired electrons in the isolated region rather than one. The way the correlations develop with decreasing temperature or decreasing magnetic field is expected to be sensitive to the geometry of the leads. Specific theoretical predictions have been made for this situation, and a major part of the work proposed for this project is designed to test these predictions. More generally, the single-electron transistors used for these studies are an outstanding laboratory for studying the physics of nanostructures, some of which may eventually have important technological applications. Research on semiconductor nanostructures has also proven to be an outstanding training ground for young physicists. Former students and postdoctoral associates educated in this group have positions in small companies, large companies and universities. A significant number of these have been women and minorities. Continued recruitment of undergraduates, graduate students and postdocs, especially women and minorities is planned.Advances in nano-science and engineering let one make transistors so small that the electrons in them behave quantum mechanically. Understanding this quantum behavior is intrinsically interesting, but it is also important for understanding how to make useful electronic devices at the nanometer length scale. When electrons are confined to nanometer length scales they can be thought of as artificial atoms. Bringing an artificial atom into close contact with a metal creates a chemical bond between the atom and the metal. This project studies how that chemical bond depends on the number of electrons in the artificial atom. Because transistors made with artificial atoms turn on and off again for every electron added to them they are called single-electron transistors. In addition to its interest for technology, research on single electron transistors has proven to be an outstanding training ground for young physicists. Former students and postdoctoral associates educated in this group have positions in small companies, large companies and universities. A significant fraction of these have been women and minorities. Continued recruitment of undergraduates, graduate students and postdocs, especially women and minorities is planned.