New measurements of persistent currents in normal metal rings Jack Harris, Assistant Professor of Physics, Yale University

One of the most remarkable predictions of the quantum theory of electronic circuits is that a small loop of non-superconducting metal can have a current flowing in it in the absence of any applied voltage. This "persistent" current is directly analogous to the orbital angular momentum of electrons in atoms, and the prediction it could be observed in realistic devices at accessible temperatures generated considerable excitement...twenty years ago. Since then, experiments in this area have produced confusing results, many of which are at odds with theory and even with other experiments. To address the resulting controversy we have developed a new type of detector for persistent currents which offers greater sensitivity and a less-invasive measurement than was previously possible. I will describe our results using this approach, which seem to give the clearest picture yet of persistent currents in normal metals.