Nonlinear AC and DC Conductivities in a Two-Subband n-GaAs/AlAs Heterostructure

TL;DR

This paper investigates the nonlinear AC and DC conductivities of a two-subband n-GaAs/AlAs heterostructure under various magnetic fields, revealing complex oscillation patterns and non-thermal nonlinear effects.

Contribution

It provides a detailed analysis of nonlinear conductivity behaviors in a two-subband heterostructure, including the distinction between heating effects and intrinsic nonlinearities.

Findings

Observation of integer quantum Hall oscillations at B > 3 T

Detection of magneto-intersubband resistance oscillations at B < 1 T

Nonlinearity in AC conductivity not explained by heating effects

Abstract

The DC and AC conductivities of the n-GaAs/AlAs heterostructure with two filled size quantization levels are studied within a wide magnetic field range. The electron spectrum of such heterostructure is characterized by two subbands (symmetric $S$ and antisymmetric $AS$), separated by the band gap $\Delta_{12}=15.5$ meV. It is shown that, in the linear regime at the applied magnetic field $B >3$ T, the system exhibits oscillations corresponding to the integer quantum Hall effect. A quite complicated pattern of such oscillations is well interpreted in terms of transitions between Landau levels related to different subbands. At $B <1$ T, magneto-intersubband resistance oscillations (MISOs) are observed. An increase in the conductivity with the electric current flowing across the sample or in the intensity of the surface acoustic wave (SAW) in the regime of the integer quantum Hall effect is determined by an increase in the electron gas temperature. In the case of intersubband transitions, it is found that nonlinearity cannot be explained by heating. At the same time, the decrease in the AC conductivity with increasing SAW electric field is independent of frequency, but the corresponding behavior does not coincide with that corresponding to the dependence of the DC conductivity on the Hall voltage $E_y$.