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The ampere: Single-electron tunneling (SET)

One ampere corresponds to the flux of approx. 6 × 1018 electrons per second. By counting the electrons, the ampere can be traced to the second. The precondition for this is that the charge of an electron is exactly known or fixed, as planned in the new SI. For this purpose, single-electron pumps are developed in semiconductor structures in order to realize a precise electrical current by electron counting.

Single-electron pumps in semiconductor structures

Working Group 2.53: Low-dimensional Electron Systems

SET, Current and Charge

Working Group 2.61: SET, Current and Charge


Operating principle of the single-electron pump investigated: single electrons, depicted as red spheres, are captured while moving from one side of a conductor (in the figure, from the left-hand side) by a “dynamic quantum well” (between the “hills” of the potential landscape depicted here), and released toward the other side. The entire procedure is repeated at the clock frequency of the AC voltage, which raises and lowers the left-hand barrier of the quantum well.

Single-electron pumps are promising candidates for the realization of a future quantum current standard, and are the subject of intensive metrological research. By means of a novel, high-precision current amplifier, PTB researchers have succeeded in proving the quantization of a current of 100 pA supplied by a single-electron pump with an accuracy which had previously been unattained: within the...

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Fundamental constants are to define the units in the International System of Units in the future (Grafik: PTB)

The second and the metre have already surged ahead. The kilogram, the ampere and the other physical base units are now trying to catch up. This is one way of describing what is currently happening in the world of metrology, in the world of measuring. The International System of Units is facing a redefinition of its foundations: fundamental constants are to serve as the defining reference values...

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Halbleiter-Einzelelektronenpumpen gelten als vielversprechende Kandidaten für ein zukünftiges Quantennormal der elektrischen Basiseinheit Ampere. An der PTB wurde jetzt erstmals ein Quantennormal aus solchen Einzelelektronenpumpen entwickelt, das einen Strom erzeugt und gleichzeitig die Präzision des erzeugten Stromes unabhängig verifiziert.

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