Anomalies in the spectra of quantum oscillations for dilute two-dimensional electronic systems
Dorozhkin S. I. , Emeleus C. J. , Whall T. E., Landwehr G. , Mironov O. A.
Magnetotransport characteristics of a two-dimensional hole gas located at a Si/SiGe heterojunction are measured for two carrier concentrations. A notable discrepancy is observed between values of the magnetic level filling factor determined from the periodicity of the Shubnikov-de Haas oscillations and the values of the Hall conductivity expected at these filling factors. In particular, the sample of lower concentration exhibits a re-entrant transition between the quantum Hall effect state and insulating state. It is shown that all the observed effects can be described by a model [S. I. Dorozhkin, JETP Lett. 60, 595 (1994)] which takes into account the long-range potential modulation in the sample, with amplitude comparable to the Fermi energy. © 1995 American Institute of Physics.