  A quantum antidot, a submicron depletion region in a two-dimensional electron
system, has been actively studied in the past two decades, providing a powerful
tool for understanding quantum Hall systems. In a perpendicular magnetic field,
electrons form bound states around the antidot. Aharonov-Bohm resonances
through such bound states have been experimentally studied, showing interesting
phenomena such as Coulomb charging, h/2e oscillations, spectator modes,
signatures of electron interactions in the line shape, Kondo effect, etc. None
of them can be explained by a simple noninteracting electron approach.
Theoretical models for the above observations have been developed recently,
such as a capacitive-interaction model for explaining the h/2e oscillations and
the Kondo effect, numerical prediction of a hole maximum-density-droplet
antidot ground state, and spin density-functional theory for investigating the
compressibility of antidot edges. In this review, we summarize such
experimental and theoretical works on electron interactions in antidots.
