QUANTIZED CURRENT IN A QUANTUM DOT TURNSTILE

We have performed RF experiments on a lateral quantum dot defined in the two dimensional electron gas (2DEG) of a GaAs/AlGaAs heterostructure. The small capacitance of the quantum dot gives rise to single-electron charging effects, which we employed to realize a quantum dot turnstile device. By modulating the tunnel barriers between the quantum dot and the 2DEG leads with two phase-shifted RF signals, we pass an integer number of electrons through the quantum dot per RF cycle. This is demonstrated by the observation of quantized current plateaus at multiples of ef in current-voltage characteristics, where f is the frequency of the RF signals. When an asymmetry is induced by applying unequal RF voltages, our quantum dot turnstile operates as a single-electron pump producing a quantized current at zero bias voltage.