Probing two-dimensional metallic-like and localization effects at low magnetic fields

The metallic-like regime characterized by Shubnikov-de Haas (SdH) oscillations is investigated between localization-induced weak insulator and quantum Hall liquid in a gated two-dimensional GaAs electron system containing InAs dots. Multiple SdH crossing points are observed in the longitudinal resistivity before the appearance of the critical point of a plateau transition with increasing perpendicular magnetic field. In conductivities, however, there is no corresponding crossing in the metallic-like regime because of the T-dependent Hall slope under electron-electron interaction, which provides an explicit way to distinguish SdH crossing points from the critical point in our study. © 2009 Elsevier B.V. All rights reserved.