Many-body interactions in a quantum wire in the integer quantum Hall regime: suppression of exchange-enhanced g factor

TL;DR

This paper investigates the collapse of Hall gaps in a quantum wire under the integer quantum Hall regime, analyzing exchange interactions, charge redistribution, and their effects on the g-factor and phase transitions, with results aligning with recent experiments.

Contribution

It extends previous models to include confinement effects and exchange-enhanced g-factors, proposing two scenarios for Hall gap collapse in quantum wires.

Findings

Exchange interaction causes collapse of the $ u=1$ state at a critical magnetic field.

Charge redistribution can induce a transition to the $ u=2$ state, affecting the critical field.

The first scenario, involving exchange effects, aligns more closely with experimental data.

Abstract

The collapse of Hall gaps in the integer quantum Hall liquid in a quantum wire is investigated. Motivated by recent experiment [Pallecchi et al. PRB 65, 125303 (2002)] previous approaches are extended to treat confinement effects and the exchanged enhanced g-factor in quantum wires. Two scenarios for the collapse of the $\nu =1$ state are discussed. In the first one the $\nu =1$ state becomes unstable at $B_{cr}^{(1)}$, due to the exchange interaction and correlation effects, coming from the edge-states screening. In the second scenario, a transition to the $\nu =2$ state occurs at $B_{cr}^{(2)}$, with a smaller effective channel width, caused by the redistribution of the charge density. This effect turns the Hartree interaction essential in calculating the total energy and changes $B_{cr}^{(2)}$ drastically. In both scenarios, the exchange enhanced g-factor is suppressed for magnetic fields lower than $B_{cr}$. Phase diagrams for the Hall gap collapse are determined. The critical fields, activation energy, and optical $g$-factor obtained are compared with experiments. Within the accuracy of the available data, the first scenario is most probable to be realized.