Magnetic response of a single, isolated gold loop

Measurements have been made of the low-temperature magnetic response of single, isolated, micron-size Au loops. The magnetic response is found to contain a component which oscillates with the applied magnetic flux with a fundamental period of 0=h/e. The amplitude of the oscillatory component corresponds to a persistent current of(0.32.0)evF/L, 1 to 2 orders of magnitude larger than predicted by current theories. © 1991 The American Physical Society.