AC and DC Conductivities in an n-GaAs/AlAs Heterostructure with a Wide Quantum Well in the Integer Quantum Hall Effect Regime

TL;DR

This study measures and analyzes the dc and ac conductivities in a wide GaAs quantum well within the integer quantum Hall regime, revealing oscillations linked to Landau level transitions and a hopping conduction mechanism at oscillation minima.

Contribution

It provides new experimental data on ac and dc conductivities in a wide quantum well, highlighting the role of Landau level transitions and the hopping mechanism in the quantum Hall regime.

Findings

Oscillations in conductivity linked to Landau level transitions.

Conductivity minima are governed by hopping mechanisms.

Frequency dependence of ac conductivity supports hopping conduction.

Abstract

The direct-current (dc) $\sigma_{xx}^{dc}$ and alternating-current (ac) $\sigma_{xx}^{ac}=\sigma_1-i\sigma_2$ conductivities of a wide (46 nm) GaAs quantum well with the bilayer electron density distribution are measured. It is found that the magnetic field dependence of $\sigma_{xx}$ exhibits three sets of oscillations related to the transitions between Landau levels in symmetric and antisymmetric subbands and with the transitions occurring owing to the Zeeman splitting of these subbands. The analysis of the frequency dependence of the ac conductivity and the $\sigma_1 / \sigma_2$ ratio demonstrates that the conductivity at the minima of oscillations is determined by the hopping mechanism.