Zero-bias transfer of single electrons in a turnstile device designed withtrapezoidal tunneling barriers

The transfer of single electrons has been theoretically studied in a turnst ile device with four identical tunnel junctions of capacitance C and a gate capacitor of capacitance C/2, designed with identical asymmetric tunneling barriers instead of symmetric tunneling barriers. The zero-current offset in the current-voltage characteristic of this turnstile is not at zero-bias voltage when the amplitude of an applied ac gate voltage is greater than e /C; that is, electrons can be transferred through the device with an applie d ac gate signal but without bias voltage. This unusual transfer characteri stic is due to a rectification nature of electron tunneling in asymmetric t unneling barriers. [S0163-1829(99)10811-7].