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

摘要

The collapse of Hall gaps in the integer quantum Hall liquid in a quantum wire is investigated. Motivated by recent experiment [Pallecchi et al., Phys. Rev. B 65, 125303 (2002)] previous approaches are extended to treat confinement effects and the exchange-enhanced g factor in quantum wires. Two scenarios for the collapse of the v= 1 state are discussed. In the first one the v= 1 state becomes unstable at B_(cr)~(1), due to the exchange interaction and correlation effects, coming from the edge-state screening. In the second scenario, a transition to the v=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.