Periodic modulation of Coulomb-blockade oscillations in high magnetic fields

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. © 1994 The American Physical Society.