Anomalies in the spectia of quantum oscillations for dilute two-dimensional electronic systems
Dorozhkin S.I., Emeleus C.J., Whall Т.Е., Landwehr G., Mironov O.A.
We have measured magnet ©transport characteristics of a two-dimensional hole gas located at a Si/SiGe heterojunction for two carrier concentrations. A notable discrepancy is observed between values of the magnetic level filling factor denned from the periodicity of the Shubnikovde Haas oscillations and values of the Hall conductivity expected for these filling factors. In particular, the sample of lower concentration exhibits a re-entrant transition between the quantum Hall effect state and insulating state. We show that all the observed effects can be described by a model [6] which takes into account long-range potential modulation in a sample, with amplitude comparable to the Fermi energy.