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

摘要

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, f_m, when the modulating microwave power is fixed. As the depth of the QD potential is deepened, f_m 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.