Single- and few-electron dynamic quantum dots in a perpendicular magnetic field

Abstract

We present experimental studies of the current pumped through a dynamic quantum dot over a wide range of magnetic fields. At low fields we observe repeatable structure indicating increased confinement of the electrons in the dynamic dot. At higher fields (B > 3 T), we observe structure which changes markedly from device to device suggesting that in this regime the transport is sensitive to local disorder. The results are significant for the development of dynamic quantum dot pumps as quantum standards of electrical current.

Non-adiabatic quantized charge pumping with tunable-barrier quantum dots: a review of current progress

“…The accuracy-enhancement effect has been confirmed in several later studies on similar devices [20,125,142,158,180,181]. For example, for a sine-wave-driven pump at f = 150 MHz the B-field was found in [20] to increase monotonically the parameter δ 2 (and hence the predicted accuracy, see Section 3.2) from about 5 at B = 0 T to 21 at B = 14 T (see Figure 19(d) below).…”

“…Quantization plateaus corresponding to Fig. 12(b) have been measured experimentally [125,132,[154][155][156][157][158], see an example in Fig. 18(a).…”

Towards a quantum representation of the ampere using single electron pumps

“…Due to the Coulomb charging energy of the dot, the back-tunnel probability for the last electron is many orders of magnitude less than for the second electron, so the convergence on the 1-electron state is robust and insensitive to details of the potential barrier shape. The GaAs pump has an important advantage compared to other types of electron pump, which is that the quantisation accuracy can be improved with an external tuning parameter, the perpendicular magnetic field B [14][15][16][17][18]. The mechanism for this improvement is not fully understood, but the additional confinement of electrons within the dot due to the magnetic field plays an important role [18].…”

Stabilization of single-electron pumps by high magnetic fields

“…All three data sets show the movement of plateaux boundaries in magnetic field. Some of this behavior has been linked to magnetic confinement 16 . At high magnetic fields, where we expect tunneling rates to be suppressed, it appears that a shift in V G2 is required to recover the same current.…”