By coincidence, TU Delft researchers have developed a superconductor that allows electricity to flow in one direction.
A superconducting diode, made up of layers one atom thick, can reduce the energy consumption of computers enormously. 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 basic component of modern computers. Diodes and transistors are made of semiconductors that have electrical resistance, which means that energy is lost in them in the form of 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 the resistance that causes electricity to flow in only one direction.
Not predicted
Mazhar Aliassistant professor of nanosciences at Delft University of Technology, and his colleagues now have a superconducting diode for the first time demonstrated† They placed a two-dimensional layer of a material called niobium-3-bromine-8 between two superconducting layers. When electrons travel in one direction through the whole, they encounter no resistance. They do experience it in the other direction.
“This was not predicted,” Ali says. “We just tried this experimentally – there was no prediction before the experiment.”
The result was so unexpected that Ali and his team don’t fully understand how the superconducting diode works. “People have a rough idea, but a rigorous theory doesn’t exist yet,” Ali says.
Hundreds of times faster
In addition to overturning theory, the discovery could also have important practical applications. Computers and data centers consume between 10 and 20 percent of all electricity in the world. A large part of it is lost in the form of heat due to the electrical resistance in transistors. By making superconducting semiconductors, computers could 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 crucial for the advancement of quantum computers. The diode uses a phenomenon called the Josephson effect, a quantum process in which electrons can tunnel through a gap between two superconductors.
So-called Josephson junctions are widely used in superconducting quantum computers. The use of a Josephson diode could 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 that involves a lot of extra physics that you wouldn’t have in a superconducting wire, for example’, says Jason Robinsonprofessor of materials physics at the University of Cambridge.
Ali and his team now want to use their discovery to build a superconducting transistor, but challenges lie 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 thinks the diode can operate 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, in which layers of superconducting material are carefully peeled off and stacked on top of each other. This should be automated to make the devices at scale, Ali says.