Artificial Atoms

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

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.