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. 3--2. 0) ev₅/L, 1 to 2 orders of magnitude larger than predicted by current theories.