High-Frequency Hopping conductivity of Disordered 2D-system in the IQHE Regime

TL;DR

This study measures high-frequency conductivity in disordered 2D systems within the IQHE regime, revealing a consistent hopping conductivity mechanism characterized by a specific ratio of conductivity components at low temperature.

Contribution

It provides experimental evidence of high-frequency hopping conductivity in disordered 2D systems under IQHE conditions, analyzing its dependence on temperature and magnetic field.

Findings

The ratio σ₁/σ₂ ≈ 0.15 indicates hopping conduction mechanism.

Conductivity components depend on temperature and magnetic field.

Landau band broadening due to impurity potential is characterized.

Abstract

High frequency (hf) conductivity in the form $\sigma^{hf} = \sigma_1^{hf} - i\sigma_2^{hf}$ was obtained from the measurement of Surface Acoustic Waves (SAW) attenuation and velocity (f=30 MHz) in GaAs/AlGaAs heterostructures ($n=1.3-7\cdot 10^{11}cm^{-2}$). It has been shown that in the Integer Quantum Hall Effect (IQHE) regime for all the samples at magnetic fields corresponding to the middle of the Hall plateaus and T=1.5 K, $\sigma_1 / \sigma_2 =0.14 \pm 0.03$. The ratio $\sigma_1 / \sigma_2=0.15$ points the case when the high-frequency hopping conductivity mechanism (electronic transition between the localized states formed by "tight" pairs) is valid \cite{1}. Dependencies of $\sigma_1$ and $\sigma_2$ on temperature and magnetic field is analyzed width of the Landau band broadened by the impurity random potential is determined.