In a two-dimensional electron system, we can confine electrons to edges using a magnetic field B.
An island ("antidot") in a sea of electrons then has a set of circulating states around it, like standing waves. We can cause tunnelling through those states by bringing other edges close by.
The conductance G has a peak or dip when a state is on resonance, lining up with the Fermi energy.
The Aharonov-Bohm effect causes these states to shrink as B increases, with the states shifting along by one each time the flux enclosed increases by h/e. Thus we see oscillations in G as shown above.
| By studying line shapes of peaks and dips we have shown that the antidot behaves very like a “quantum dot”, showing Coulomb charging as extra electrons are added, and many-body and spin effects such as the Kondo effect. |  |
These results leave many questions unanswered, and there is now plenty of scope to investigate many-body, spin and charging effects in more detail and in other regimes. With our new high-resolution lithography we will also be able to combine antidots, charge detectors, spin filters and other quantum devices with ease.
A printable (PDF) description of this project is available here (128kB).
For more information, please contact Prof Chris Ford.