Single-parameter nonadiabatic quantized charge pumping

Abstract

Controlled charge pumping in an AlGaAs/GaAs gated nanowire by single-parameter modulation is studied experimentally and theoretically. Transfer of integral multiples of the elementary charge per modulation cycle is clearly demonstrated. A simple theoretical model shows that such a quantized current can be generated via loading and unloading of a dynamic quasi-bound state. It demonstrates that non-adiabatic blockade of unwanted tunnel events can obliterate the requirement of having at least two phase-shifted periodic signals to realize quantized pumping. The simple configuration without multiple pumping signals might find wide application in metrological experiments and quantum electronics.PACS numbers: 73.23.Hk,73.22.Dj,73.63.Kv An important milestone in the study of single electron transport is the closure of the quantum metrological triangle for frequency, dc current, and dc voltage [1]. Dc voltage is currently realized from the frequency standard through the Josephson effect. Dc current can then be derived using the quantum Hall effect. Direct realization of dc current from frequency is the currently missing side of the triangle. The closure of the quantum metrological triangle provides a test whether the fundamental constants really appear the same in these different systems [2]. The results of this kind of experiment will also impact on a future system of units which might be based on fundamental constants [3].A current source relevant for the above experiments must produce at least nanoampere currents to be measurable with sufficient accuracy. The electron pump based on arrays of Coulomb blockaded quantum dots (see [4] for a review) or quantum interference [2,5,6] is one class of devices being investigated with respect to metrological relevance [7,8,9]. Electron pumps are typically driven by multiple radio frequency (rf) signals with a well maintained phase relationship, producing a quantized current, i.e. limited to certain values according to I = −nef (with n = 1, 2, 3 . . . , e the negative elementary charge and f the driving frequency). Usually, the accuracy in I degrades with increasing f , which has so far prevented the generation of sufficiently accurate nanoampere currents. An alternative, but challenging task would be the parallelization of pumps driven at intermediate frequencies. Here, pumps requiring only a single rf signal would fundamentally reduce the complexity in the parallelization of such devices. However, electron pumps driven by only one gate [10,11,12,13] have so far not experimentally demonstrated the generation of quantized current. In addition, most models of quantized pumping [5,6,14,15,16,17] have assumed at least two parameters modulated out phase, which may be motivated by the fact that in the adiabatic limit a single periodic perturbation cannot determine the direction of the current [18].In this paper we address this issue and report on the first experimental realization of quantized charge pumping in which only one gate is modulated. We demonstrate on a transparent quantu...

An Accurate Single-Electron Pump Based on a Highly Tunable Silicon Quantum Dot

“…This device ideally generates a quantized output current, I P = nef , where n is an integer and f is the frequency of an external periodic drive. Several enabling technologies have already been developed including metal/oxide tunnel barrier devices 6,7 , normal-metal/superconductor turnstiles 8,9 , graphene double quantum dots 10 , donor-based pumps [11][12][13] , silicon-based quantum dot pumps [14][15][16][17][18] and GaAs-based quantum dot pumps [19][20][21][22][23][24][25][26][27] . To date, the latter scheme provides the lowest uncertainty of 1.2 parts per million (ppm) yielding current in excess of 150 pA 27 .…”

Time-of-Flight Measurements of Single-Electron Wave Packets in Quantum Hall Edge States

“…Electrons are emitted from a tunable-barrier single-electron pump [26][27][28] approximately 100 meV above the Fermi energy [13,29]. These electrons are injected into an edge where the background two-dimensional electron gas (2DEG) is depleted to avoid the influence of electron-electron interactions.…”

Nonadiabatic charge pumping by oscillating potentials in one dimension: Results for infinite system and finite ring

“…(44)(45), we see that the ± sign in Eq. (48) corresponds to two solutions v ± (t) which satisfy U (T )v ± (0) = e iθ± v ± (0), where e iθ± = e −iE1T 1 − iαT c 20 c 10 = e −iT (E1±|α|) (49) to first order in α. We thus see that the degeneracy of eigenvalues of U 0 (T ) is broken at first order in V , with the phases θ ± being split by equal and opposite amounts.…”

“…The idea that oscillating potentials applied to certain points in a one-dimensional system can pump a net charge between two reservoirs at the same chemical potential has been studied extensively for many years, both theoretically and experimentally [43][44][45][46][47][48][49]. For the case of non-interacting electrons, theoretical studies of this phenomenon have used adiabatic scattering theory [9][10][11][12][13][14][15][16][17], Floquet scattering theory [21][22][23], the nonequilibrium Green function formalism [24][25][26][27], and the equation of motion approach [36,37].…”

“…With the exception of a few papers [22,[24][25][26][27]49], the earlier studies of charge pumping have generally considered systems in which oscillating potentials are applied to two or more sites. In such cases, it is known that if the oscillation frequency ω is small, the dc part of the pumped current is proportional to ω; the charge pumped per cycle (with time period 2π/ω) therefore has a finite value in the adiabatic limit ω → 0.…”