Coulomb-blockade oscillations in transport through a lateral quantum dot at small Landau-level filling factors are investigated. We observe both a periodic modulation of the peak conductance as well as a striking modulation of the peak separation. We show that below a Landau-level filling factor of 3 a single-particle description of these effects fails and the depopulation of the Landau levels with decreasing electron number can occur noncyclically. We interpret our measurements in terms of a recently developed phase diagram that characterizes the states of the quantum dot.

• Received 28 June 1994

DOI:https://doi.org/10.1103/PhysRevB.50.15113