Insulator-quantum Hall transition in n-InGaAs/GaAs heterostructures

Abstract

The longitudinal ρxx(B,T) and Hall ρxy(B,T) resistances in magnetic fields B up to 12 T at temperatures T = 1.8–80 K are studied experimentally in n-In0.2Ga0.8As/GaAs nanostructures with single and double strongly-coupled quantum wells separated by different barrier widths. It is shown that for ω c τ ≅ 1 there is a critical magnetic field near which the scaling relation ρ x x ∝ | B − B C | T − κ, which is indicative of a phase transition from a dielectric state to a quantum hall state, is satisfied. It is found that the critical index κ depends on the width of the barrier between the double quantum wells. The nature of this behavior is discussed.