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 ν=1 state are discussed. In the first one the ν=1
state becomes unstable at Bcr(1)​, due to the exchange interaction and
correlation effects, coming from the edge-states screening. In the second
scenario, a transition to the ν=2 state occurs at Bcr(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 Bcr(2)​ drastically. In both scenarios, the
exchange enhanced g-factor is suppressed for magnetic fields lower than
Bcr​. 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.Comment: 11 pages, 10 figure