From measurements of the oscillatory magnetoresistance in weak perpendicular magnetic fields, we found that the quantum oscillations in two-dimensional electron systems in Si-MOS structures are observed down to the critical carrier density nc of the transition to the strongly localized state. For such low densities, the oscillations exhibit an anticipated period, phase, and amplitude, even though the conductivity becomes less than e2/h, and, hence, the mean free path becomes less than the Fermi wavelength λF. We believe that this apparent contradiction with the Ioffe-Regel criterion for diffusive transport is caused by emergence of an inhomogeneous state of the 2D system, in which the regions of diffusive and hopping conduction are spatially separated.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)