Twisted graphene can strengthen a new generation of superconducting electronics | Science

Twisted graphene can strengthen a new generation of superconducting electronics |  Science

A model of twisted graphene reveals a moirയർ pattern of its remarkable qualities.

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Charlie Wood

In 2018, a group of researchers at the Massachusetts Institute of Technology (MIT) withdrew the astonishing materials science magic trick. They stacked two microscopic cards, graphene car carbon sheets the thickness of an atom – and twisted one slightly. Applying an electric field transfers the stack from one conductor to the insulator and then quickly to a superconductor: a material that conducts electricity without friction. Dozens of labs are rushing into the newly born “Twistronics” field without any hindrance in combining chemically different materials.

Two groups are now fulfilling that promise, including the superconducting switches used in many quantum computers, and the pioneering MIT group in converting distorted graphs into functional tools. Studies mark a critical stage for a material that is already maturing into a basic scientific tool that can capture and control individual electrons and photons. Now, it offers the basis of new electronic equipment, says Corey Dean, an evaporative physicist at Columbia University, who said the lab is the first lab to confirm the material’s superconducting properties since its announcement in 2018. “The idea that this platform can be used as a universal material is not fantasy,” he says. “It simply came to our notice then.

A secret similar to the twisted graphene me herb is called the “magic angle”. When the researchers turn the sheets exactly 1.1 by, the twist creates a large “moir” pattern that is equal to the atom-scale of the dark bands seen when the two grids are connected to each other. By bringing thousands of atoms together, Moire allows them to work together like superautoms. That collective behavior enables moderate amounts of electrons to be maintained in the right place by the electric field, to radically change the nature of the material, from the insulator to the superconductor. Interaction with supercells causes electrons to slow down and feel their presence near each other, making it easier to pair the requirement for superconductivity.

Researchers have now shown that the desired properties can be dialed into small areas of the sheet by sleeping with a pattern of metal “gates” that subject different areas to different electric fields. Both groups manufactured devices known as Josephson junctions, in which the two superconductors consist of a thin layer of superconducting material that creates a valve to control the flow of superconductivity. “Once you prove that the world is open,” Klose Enzoulin, a physicist and co-author of a study on ETH Zurich, posted on the Prixprint server arXiv on October 30th. Conventional Josephson junctions act as a workhorse for superconducting electronics, found in magnetic devices for monitoring electrical activity in the brain, and ultrasonic magnetometers.

The MIT Group went even further, electroplating their Josephson junctions to other submicroscopic gadgets, “as proof of the idea, to show just how diverse it is,” says lab leader Pablo Gerillo-Herero, who posted the results on November 4. By tuning the carbon into a conductor-insulator-superconductor configuration, they were able to measure how much electron pairs were visually absorbed, an early indication of the nature of its superconductivity and how it compares to other materials. The team also developed a transistor that could control the movement of single electrons; Researchers have studied such single-electron switches as a way to shorten circuits and reduce the thirst for energy.

Magic angle graphene devices are unlikely to challenge consumer silicon electronics at any time. Graphine itself is easy to make: blocks of graphite can be removed from its sheets with nothing but scotch tape. But the equipment must be cooled to almost zero before superconnecting. Maintaining the exact twist is difficult because the sheets fall into wrinkles and interfere with the magic angle. Reliably creating smoothly twisted sheets of even 1 micron or two is still a challenge, and researchers have yet to see a clear path to mass production. “If you want to make a truly sophisticated tool, you have to create millions [graphene substrates] That technology does not exist. ”

However, many researchers are excited at the promise of being able to explore electronic devices without having to worry about the limitations of chemistry. Materials scientists usually need to find materials with the right atomic properties and combine them together. When the collection is complete, do not mesh the different components as needed.

In the magic angle graphene, by contrast, all atoms are carbon, eliminating the distortions between different materials. Scientists can change the electronic nature of any patch with the press of a button. These properties give the material unprecedented control, says Enzoline. “Now, you can play like a piano.”

Quantum computers can simplify that control. Developers of Google and IBM rely on Josephson junctions with properties specified during fabrication. In order to execute subtle quits, the junctions must be handled in a complex manner. With twisted graphene, quits can come from single junctions that are small and easy to control.

Kin Chung Fong, a Harvard University physicist and member of the quantum computing team at Raytheon BBN Technologies, is excited about another use for the material. In April, he and his colleagues suggested a twisted graphene device that could detect a single photon of infrared light. This would be useful for astronomers examining the dim light of the early universe; Their current sensors can only detect single photons in visible or almost visible parts of the spectrum.

The field of Twistronics remains in its infancy, and the process of twisting graphene’s microscopic scoops into a magical position still requires handshake or at least deft lab work. Regardless of whether the distorted graphene finds its way into industrial electronics, it is already deeply changing the world of material science, says Eva Andrei, a distorted graphene of distorted graphics at Rutgers University’s Rutgers University in New Brunswick. Properties.

“This is a new era,” she says. “It’s a whole new way of making materials without chemistry.”

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