A superconducting diode built from a sandwich of atom-thick layers could save vast amounts of power in traditional computing and transform superconducting quantum computers.
The diode 鈥� an electronic component that lets electricity preferentially travel in one direction 鈥� is a fundamental part of the transistor, the foundational component of modern computing. Diodes and transistors are made from semiconductors that have electrical resistance, meaning energy is lost in the form of heat.
Superconductors are materials with no resistance and so no energy loss, but they don鈥檛 work as diode components, since resistance is how traditional diodes ensure that electricity travels in only one direction.
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Now, at Delft University of Technology in the Netherlands and his colleagues have demonstrated a superconducting diode for the first time. They sandwiched a 2D layer of a material called niobium-3 bromine-8, which is thought to have a built-in electric field, between two 2D superconducting layers. When electrons travel through the structure in one direction, they don鈥檛 encounter resistance, but in the other direction they do.
鈥淔rom a fundamental perspective, this was not predicted,鈥� says Ali. 鈥淲e experimentally just did this 鈥� there was no prediction prior to this experimental realisation.鈥�
The result was so unexpected that Ali and his team don鈥檛 fully understand how the superconducting diode works. 鈥淧eople have a rough idea, but a rigorous theory does not exist yet,鈥� says Ali.
Apart from rewriting theory, the discovery could also have important practical applications. between 10 and 20 per cent of the world鈥檚 electricity supply, much of which is wasted as heat from electrical resistance in transistors. Creating superconducting semiconductors could make computers use hundreds of times less power and possibly run at hundreds of times faster speeds, says Ali.
In addition to saving energy, the diode could be crucial for advances in quantum computing. It employs a phenomenon called the Josephson effect, a quantum process that allows electrons to tunnel across a gap between two superconductors.
Josephson devices are widely used in superconducting quantum computing, but the introduction of a Josephson diode could transform the kinds of quantum computers that can be built.
鈥淲hat鈥檚 particularly impressive about this result is the fact that you also have a Josephson device, because that introduces a whole bunch of additional physics which you wouldn鈥檛 have, for example, in a superconducting wire,鈥� says at the University of Cambridge.
Ali and his team now aim to use their discovery to build a superconducting transistor, but there are challenges ahead. Their current diode operates at around 2 kelvin, or -271掳C, which requires more energy to maintain than the diode might feasibly save.
Ali thinks that alternative materials could be used to make the diode work at temperatures above 77 K, the temperature at which nitrogen is liquid, which would make the diodes energy-saving.
The diode is also constructed in a manual process, which involves carefully peeling off layers of superconductor and stacking them. This would have to be automated for the large-scale production of these devices, says Ali.
Nature
