Magnetic field modulation-a method for measuring the Hall conductance with a Corbino disc
For the first time a method is given to determine the Hall conductivity on a Corbino disc with an electrical transport experiment. Use has been made of a time-modulated magnetic field to induce currents in the disc. First measurements were carried out on GaAs/AlGaAs heterojunctions in the quantised Hall regime. Instead of the expected plateaus, oscillations as a function of the magnetic field were found. It is shown that an inhomogeneous electron gas density can account for the observations.