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Semiconductor Physics Group


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.

AB oscillations

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. AB 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.