CONDUCTANCE FLUCTUATIONS IN A RECTANGULAR DOT AT CONSTANT MAGNETIC-FIELDS

A systematic experimental and theoretical study has been performed on the conductance oscillations of a rectangular dot as a function of the dot width at different Fred magnetic fields (including zero field). W e provide a semiclassical interpretation of the fluctuations at zero a nd very low magnetic fields (less than or similar to 0.05 T) in terms of specific families of periodic orbits, which occur in a classical re ctangular billiard. At higher magnetic fields (0.2 less than or simila r to B less than or similar to 0.25 T) the fluctuations become more ap eriodic with reduced amplitudes while the Fourier spectrum contains no significant peaks. With a further increase in the field the cyclotron orbit fits within the dot and now a single frequency dominates the fl uctuations, which is consistent with the (semi)classical predictions i n this field region. Finally, as the edge-state regime is reached, Aha ronov-Bohm oscillations take over. [S0163-1829(98)02839-2].