Upper frequency limit depending on potential shape in a QD-based single electron pump

Abstract

Our quantum-dot (QD) electron pump has uniqueness in design in that the QD potential shape can be manipulated, especially its potential depth can be controlled by a plunger gate. We find that there exist strong correlations between the potential depth of the QD and the upper frequency limit, fm, when the modulating microwave power is fixed. As the depth of the QD potential is deepened, fm shows decreasing characteristics while the flatness of the 1st current plateau is increased. We have semi-quantitatively analyzed these correlations by using the notion of so-called "non-adiabatic Coulomb blockade gap energy," ΔELU. We find that ΔELU parameter being under control by a plunger gate is proportional to the pumping frequency f.