Nano-Device Generates Electricity by Hurdling Electrons

Researchers found a new way of generating an electric current with an electron pump, which brings about a new level of accuracy that could soon be used to calibrate machinery. The study was done by researchers at the National Physical Laboratory (NPL) and the University of Cambridge.

Using a single-electron pump, they jump electrons over a barrier one at a time. Electrical currents are created by the rapid movement of electrons, typically by the billions, and this machine moves them in a more organized, more effective manner by adjusting the speed of movement.

The machine itself is a nano-device, and being very small, so too is the barrier over which the electrons move. There’s a hole in the center of this barrier measuring just 0.0001 mm across that plays a key role in all of this. It traps the electrons in this tiny notch, then ejects them.

Masaya Kataoka, senior research scientist in the Quantum Detection Group at NPL, said this trapping and ejecting is what creates the current.

“Because the charge of an individual electron is tiny, the signal is repeated many times a second to generate a large enough current,” Kataoka said via email.

The idea of using a single-electron pump to study electrical currents is nothing new, but the real breakthrough here was that they achieved a new level of speed and accuracy.

Researchers were able to pump close to a billion electrons per second, which is about 300 times faster than the previous record, set by the National Institute of Standards and Technology (NIST) in 1996.

The problem with speeding up the process is that the faster it moves, the less accurate it becomes. Kataoka said, “Many schemes have been proposed, but they all have a fundamental problem of not being able to produce a large enough current accurately.”

They found a way around this though by starting slow, then gradually speeding up the system. “This enabled us to produce a large enough current,” Kataoka said.

Kataoka compared this to trying to scoop helpings from a filled bowl of soup, noting, “If you lift the spoon slowly, you can fill it up to the brim. On the other hand, if you dig the spoon into the bowl and lift it up quickly, the chance is that your spoon is only partly filled.”

“This is because if you move the container (in this case the spoon) of fluid fast, it can induce a wave motion of the fluid, and some portion will spill out of the container,” Kataoka said. “Now, an electron is not exactly fluid, but the probability of finding it in a certain position behaves like fluid.”

According to Kataoka, the new finding isn’t likely to find its way into consumer products anytime soon, “but it could be used to calibrate the accuracy of electrical components (such as resistors and capacitors) and equipment (such as ammeters), which indirectly affects the quality of life.”

To reach a stage where this method could be more effective than methods already in use, Kataoka said, yet noted, “if we can improve the accuracy further (say, by a factor of 10), the advantages of our pumps (simple operations, stability etc.) may win over other methods, and I expect that some of the calibration services will start using electron pumps.”

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