Enhanced current quantization in high-frequency electron pumps in a perpendicular magnetic field

We present experimental results of high-frequency quantized charge pumping through a quantum dot formed by the electric field arising from applied voltages in a GaAs/AlGaAs system in the presence of a perpendicular magnetic field $B$. Clear changes are observed in the quantized current plateaus as a function of applied magnetic field. We report on the robustness in the length of the quantized plateaus and improvements in the quantization as a result of the applied $B$ field.

Figure 1

Pumped current as a function of $V_2$. Here, $V_1=-0.140V$ and $V_1^{\text{ac}}=306.7\text{MHz}$ at $-12\text{dBm}$. Plateaus are visible at currents corresponding to a quantized number of electrons pumped per cycle. The expected values for these plateaus are shown as dashed lines in the figure. Inset is an SEM image of the device, including a schematic of the electrical connections.

Figure 2

Pumped current as a function of applied perpendicular $B$ field. Each line represents a different voltage $V_2$, explained in more detail in text. The v’s along the upper borders highlight the features of interest. Sweep rates of 5 and 20 T/h were used in (a) and (b), respectively.

Figure 3

Evolution of the quantized pumped current plateaus in applied $B$ field. The numbers in the grayscale bar indicate the number of electrons pumped per cycle.

Figure 4

(Color online) Pumped current for the first plateau. (a) shows the pumped current at 0 T (red solid curve) and 2.5 T (blue dashed curve). Dot-dashed lines correspond to the expected plateau values. (b) and (c) show the numerical derivative of the pumped current. (d) and (e) are expanded regions indicated by the black boxes in (b) and (c) over which the gradient of each plateau was calculated.