A tunable quantum ring in the limit ofstrong tunnel coupling

摘要

We use current-controlled local oxidation with an atomic force microscope for thefabrication of a small quantum ring. Due to the small diameter of less than 300 nm the quantumring contains less than 10 electrons in the Coulomb-blockade regime. In the limit of strongtunnel coupling to the leads we observe a Kondo effect. The Kondo effect is characterized bytemperature-dependent conductance measurements. We observe abrupt phase changes by πat the Coulomb-blockade resonances in the Kondo regime. Additionally, the conductance ismodulated by a perpendicular magnetic field due to the Aharonov-Bohm effect.