AC MEASUREMENTS OF EDGELESS CURRENTS IN A CORBINO RING IN THE QUANTUMHALL REGIME

Measurements have been made of radial currents in a two dimensional el ectron gas in the quantum Hall regime using a Corbino ring geometry. A small solenoid is used to modulate the flux linking a high mobility G aAs-AlxGa1-xAs Corbino ring, thereby inducing an alternating radial cu rrent flow. Plateaus of current value are observed giving a clear indi cation that quantization in this geometry occurs for bulk, opposed to edge, charge transport. We find that the Corbino ring behaves as a qua ntised a.c. current source over a wide range of loading resistance val ues and several decades of frequency. The internal impedance of that c urrent source is much larger than the Hall resistance and is dominated by the internal capacitance of the ring. (C) 1997 Elsevier Science Lt d.