Evidence for edge currents in the integral quantum Hall effect

In high-mobility GaAs/${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As heterostructures at magnetic fields below well developed integral quantum Hall effect plateaus, we have observed that the magnetoresistance is independent of the device channel width in sufficiently small channels. Additionally, the current distribution within the channel depends on the total current magnitude and direction. We interpret our observations with a model in which current flows primarily along the edges of the sample when small currents are applied.