Quantum Hall induced currents and the magnetoresistance of a quantum point contact

TL;DR

This study investigates quantum Hall induced currents and their impact on quantum point contact conductance, revealing correlated features at specific Landau-level fillings and differences in decay behavior, enhancing understanding of quantum Hall effects.

Contribution

It demonstrates the correlation between induced currents and QPC conductance features, and analyzes their temperature, sweep rate, and noise dependencies, providing new insights into quantum Hall phenomena.

Findings

Features in magnetic moment and resistance are correlated at specific filling factors.

Induced currents influence QPC electrostatics but are not affected by the QPC.

Decay behaviors of induced currents differ when the magnetic field is halted.

Abstract

We report an investigation of quantum Hall induced currents by simultaneous measurements of their magnetic moment and their effect on the conductance of a quantum point contact (QPC). Features in the magnetic moment and QPC resistance are correlated at Landau-level filling factors nu=1, 2 and 4, which demonstrates the common origin of the effects. Temperature and non-linear sweep rate dependences are observed to be similar for the two effects. Furthermore, features in the noise of the induced currents, caused by breakdown of the quantum Hall effect, are observed to have clear correlations between the two measurements. In contrast, there is a distinct difference in the way that the induced currents decay with time when the sweeping field halts at integer filling factor. We attribute this difference to the fact that, while both effects are sensitive to the magnitude of the induced current, the QPC resistance is also sensitive to the proximity of the current to the QPC split-gate. Although it is clearly demonstrated that induced currents affect the electrostatics of a QPC, the reverse effect, the QPC influencing the induced current, was not observed.