Super, triple twisted

American physicists have made another advance in superconductor development, building on existing knowledge to create something capable of working at higher – even close to room – temperature.

The work expands on a 2018 discovery: that an ultrathin layer of carbon called graphene could be stacked and twisted at a “magic angle” to form a double-layered structure that converts into a superconductor. This research field is known as “twistronics”.

The Harvard researchers successfully stacked three sheets of graphene and then twisted each of them at the magic angle – 1.1 degrees – to produce a three-layered structure that’s capable of superconductivity more robustly and at higher temperatures than many of the double-stacked graphene.

Their work has just been published in the journal Science.

Physicists see superconductors – a substance that allows electricity to flow without resistance or energy waste – as an avenue for technological revolution in such areas as electricity transmission, transportation, and quantum computing.

But most known superconductors, including the double-layered graphene structure, work only at ultracold temperatures.

A one-atom-thick layer of carbon atoms, graphene is 200 times stronger than steel yet extremely flexible and light. It’s recognised as a good conductor of heat and electrical current but is notoriously difficult to handle.

The triple-layer system has useful research properties, including its sensitivity to an externally applied electric field that allows scientists to tune the level of superconductivity by adjusting the strength of the field.

“It enabled us to observe the superconductor in a new dimension and provided us with important clues about the mechanism that’s driving the superconductivity,” says study co-lead author Zeyu Hao, who works with Harvard physicist Philip Kim.

The researchers are planning further studies to explore this unusual superconductivity.

“The more we understand, the better we have a chance to increase the superconducting transition temperatures,” says Kim.

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