New measurements of persistent currents in normal metal rings

by Jack Harris (Yale University)

Monday 17 Nov 2008, 11:00 → 12:00 Europe/Stockholm

122:028 (hus 12)

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 circulating 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, the handful of experiments in this area have produced confusing results, many of which are at odds with theory and even with other experiments. In an effort to address the controversies which have arisen, 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.