On the coexistence of localization and semiclassical transport in the low-field quantum Hall effect

Magneto-transport measurements are performed on the two-dimensional electron system (2DES) in an AlGaAs/GaAs heterostructure. In the integer quantum Hall effect (IQHE) at low magnetic fields, the amplitudes of magneto-oscillations can follow the semiclassical Shubnikov–de Haas (SdH) formula even when the thermal activation is suppressed. Such oscillations, together with the finite resistance near SdH oscillation minima at low temperatures, reveal the insufficient localization in the low-field IQHE although the localization effect can still induce the mobility gap.

► Coexistence of localization and semiclassical transport at low fields.
► Magnetotransport data shows anomalous hopping at low temperatures.
► Evidence for insufficient localization in the low-field quantum Hall effects.