Persistent currents through a quantum dot

We study the persistent currents induced by the Aharonov-Bohm effect in a closed ring that either embeds or is directly side coupled to a quantum dot at Kondo resonance. We predict that in both cases, the persistent current is very sensitive to the ratio between the length of the ring and the size of the Kondo screening cloud, which appears as a fundamental prediction of scaling theories of the Kondo effect. Persistent-current measurements provide therefore an opportunity to detect this cloud, which has so far never been observed experimentally.