Shell structure of a circular quantum dot in weak magnetic fields

The conductance of a circular quantum dot in a two-dimensional electron gas of a GaAlAs/GaAs heterostructure has been measured. Conductance oscillations as functions both of the magnetic field B and of the size of a dot confining about 1000 electrons are related to the formation of electronic shell structure. Modeling the dot by a circular billiard, we interpret the results semiclassically in terms of periodic orbit theory, providing a simple explanation of the B-periodic oscillations. A comparison to a harmonic confinement suitable for smaller quantum dots is given.