ROLE OF DISPLACEMENT CURRENT IN QUANTUM-DOT TURNSTILE DEVICES

The dynamics of the current and the electron number in quantum-dot tur nstile devices, in which the heights of the tunneling barriers are mod ulated by external rf signals, is studied theoretically within the adi abatic approximation. The displacement current is more accurately quan tized than the tunneling currents flowing through both the left and th e right barriers, since the leakage current is compensated. We find nu merically that an electron tunnels through the barrier before its heig ht reaches the minimum value. The tunneling phases of rf signals, at w hich an electron can actually tunnel, change as the amplitude of rf si gnals and the barrier height and width are varied. We also discuss the conditions for the current quantization, The dc I-V curve which We ob tain shows a plateau at each quantized current nef with width e(2)/C Delta E and sharp steps between neighboring plateaus. Whenever the de current is quantized, the change of the number of electrons in the qu antum dot during one half-period of rf signal is an integer.