Flux-cancellation effect on narrow-channel magnetoresistance fluctuations

The magnetic-field correlation function of the universal conductance fluctuations (UCF) in a laterally confined two-dimensional electron gas is calculated in the high-mobility regime. Boundary scattering induces cancellations of the magnetic flux enclosed by electron trajectories, which leads to an enhanced correlation field. The theory is discussed in relation to a recent observation of UCF in a narrow GaAs-${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As heterostructure.