Dynamics of a single-atom electron pump

Abstract

Single-electron pumps based on isolated impurity atoms have recently been experimentally demonstrated. In these devices the Coulomb potential of an atom creates a localised electron state with a large charging energy and considerable orbital level spacings, enabling robust charge capturing processes. In contrast to the frequently used gate-defined quantum dot pumps, which experience a strongly time-dependent potential, the confinement potential in these single-atom pumps is hardly affected by the periodic driving of the system. Here we describe the behaviour and performance of an atomic, single parameter, electron pump. This is done by considering the loading, isolating and unloading of one electron at the time, on a phosphorous atom embedded in a silicon double gate transistor. The most important feature of the atom pump is its very isolated ground state, which is populated through the fast loading of much higher lying excited states and a subsequent fast relaxation process. This leads to a substantial increase in pumping accuracy, and is opposed to the adverse role of excited states observed for quantum dot pumps due to non-adiabatic excitations. The pumping performance is investigated as a function of dopant position, revealing a pumping behaviour robust against the expected variability in atomic position.

Unusual Quantum Transport Mechanisms in Silicon Nano-Devices

“…Finally, although there are still a few open questions in this area, for example see Reference [ 4 ], the achievements described above have translated into improved control of the electronic signature that can be observed in these devices. This, in turn, explains why these systems have also been used recently as platforms for the observation of some of the most remarkable effects in physics [ 4 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ], in the same manner in which they were previously observed in other materials such as carbon nanotubes and graphene [ 6 , 7 ].…”

“…To provide further details, this review paper aims at discussing how silicon CMOS compatible ultra-scaled devices can be used for the study of very elusive problems, for example the orbital Kondo effect [ 8 , 9 ], the Kondo-Fano effects [ 10 , 11 ] as well as the mechanism of errors in single electron pump (SEP) devices [ 12 , 13 , 14 , 15 ].…”

“…In view of this, it is now possible to obtain extremely precise control of the quantum properties of electrons confined in silicon CMOS compatible structures even during fabrication [ 4 , 5 ] and it is also possible to engineer devices precise to a single atom level [ 21 , 22 , 23 , 24 ]. These new enhanced fabrication capabilities have translated into an improved ability for the control of all the quantum degrees of freedom (for example spin, charge, pseudo-spin) of electrons [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 20 , 21 , 22 , 23 , 24 ] and holes [ 25 ] in silicon nanostructures [ 4 , 5 ]. Finally, although there are still a few open questions in this area, for example see Reference [ 4 ], the achievements described above have translated into improved control of the electronic signature that can be observed in these devices.…”

“…These degeneracies can in turn be broken by all other atomic effects that go under the name of valley-splitting see Figure 1 a). For isolated dopant-atoms in the silicon lattice, i.e., single atom transistors [ 8 , 9 , 10 , 11 , 12 , 13 , 17 , 21 , 22 , 23 , 24 ], in the most ideal situation, the final configuration gives a 1-fold degenerate 1s state (A1), below a 3-fold degenerate 1s and another 2-fold 1s state, as shown in Figure 1 b), while other intermediate situations are possible [ 8 , 9 ]. As an example, the lower energetic valley-orbital states are fundamental for the observation of the Kondo and the Kondo-Fano effects described in the section below.…”

“…As an example, the lower energetic valley-orbital states are fundamental for the observation of the Kondo and the Kondo-Fano effects described in the section below. These properties are also a fundamental ingredient for the successful operation at high frequency (≥GHz) of silicon based quantum electrons pumps [ 12 , 13 , 14 , 15 ].…”