Electrical characteristics of two Coulomb blockade devices driven by a periodically oscillating potential

We describe the electrical characteristics of two multiple tunnel junction Coulomb blockade devices connected in series and separated by an island, which is large enough for Coulomb blockade phenomena in the island to be neglected. A sine wave rf signal applied to this island results in a current, which switches its polarity depending on the magnitude and sign of the gate voltages applied to the multiple tunnel junctions, even if the source drain voltage across the entire circuit is nonzero. We show that the transport mechanism responsible for this current is strongly related to the Coulomb blockade characteristics of the multiple tunnel junctions, which need to be asymmetric to achieve pump operation. The circuit characteristic can be explained theoretically by a bidirectional electron pump, which is therefore inherently different from conventional electron pumps driven by multiple ac signals. (C) 2001 American Institute of Physics.