Delft unidirectional superconductor can reduce computer energy consumption – New Scientist

By chance, researchers at TU Delft have developed a superconductor that allows electricity to flow in one direction.

A superconducting diode, consisting of an atom-thick layer, could enormously reduce the power consumption of computers. It could also be a breakthrough for superconducting quantum computers.

A diode is an electronic component that allows current to flow in one direction. It is a fundamental part of the transistor, the fundamental component of modern computers. Diodes and transistors are made of semiconductors that have electrical resistance, which means that energy is lost as heat.

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Superconductors have no resistance. As a result, no energy is lost. However, they cannot be used as diodes, because with traditional diodes it is precisely the resistance that ensures that the electricity only flows in one direction.

Not predicted

Mazhar Ali, assistant professor of nanoscience at Delft University of Technology, has now demonstrated a superconducting diode for the first time with his colleagues. They placed a two-dimensional layer of a material called niobium-3-bromine-8 between two superconducting layers. As electrons move through it all in one direction, they experience no resistance. They do in the other direction.

“This was not predicted,” says Ali. “We just tried this experimentally—there was no pre-experimental prediction.”

The result was so unexpected that Ali and his team do not fully understand how the superconducting diode works. “People have a rough idea, but a rigorous theory doesn’t exist yet,” says Ali.

Hundreds of times faster

In addition to overturning theory, the discovery may also have important practical applications. Computers and data centers consume between 10 and 20 percent of all electricity in the world. Much of this is lost as heat through the electrical resistance of transistors. Making superconducting semiconductors could allow computers to use hundreds of times less power and potentially run hundreds of times faster, Ali said.

The diode not only saves energy, but could also be critical to the progress of quantum computers. The diode uses a phenomenon called the Josephson effect, a quantum process that allows electrons to tunnel through a gap between two superconductors.

So-called Josephson junctions are widely used in superconducting quantum computers. The use of a josephson diode can therefore lead to new types of quantum computers.

Energy inefficient

‘What’s particularly impressive about this result is the fact that you have a josephson device. Because it involves a lot of extra physics that you wouldn’t have, for example, in a superconducting wire,’ says Jason Robinson, professor of materials physics at the University of Cambridge.

Ali and his team will now use their discovery to build a superconducting transistor, but there are still challenges ahead. The current diode operates at about 2 Kelvin, or -271 degrees Celsius. It takes more energy to maintain that temperature than the diode could save.

Ali believes that the diode can work with alternative materials at temperatures above 77 Kelvin – the temperature at which nitrogen is liquid. That would make the diodes energy-saving.

Furthermore, the diode is currently still made in a manual process where layers of superconducting material are carefully peeled off and stacked on top of each other. This would need to be automated to make the devices scale, says Ali.

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