"Magic-Angle" Graphene Studies Could Open a Door to High-Temperature Superconductors, Quantum Chips

A team of researchers from the Massachusetts Institute of Technology (MIT) and the Weizmann Institute of Science have published a pair of papers on what they call "magic-angle" graphene — a material which could be used to create high-temperature superconductors or quantum computing hardware.

Graphene, a single-atom-thick material made from carbon, is often considered a wonder-material for a variety of devices — including smart textiles, wearable health sensors, and even an enhanced force-detecting Silly Putty dubbed "goophene." In 2018, MIT scientists took the material a stage further by discovering that its properties can be changed by stacking graphene sheets at different angles — converting it between being an insulator to a superconductor.

The resulting science of "twistronics" has been a subject of focus ever since, and now MIT has announced the successful imaging and mapping of a twisted graphene structure in its entirety — key to understanding how to manipulate its properties.

“This is the first time an entire device has been mapped out to see what is the twist angle at a given region in the device,” says Pablo Jarillo-Herrero, the Cecil and Ida Green Professor of Physics at MIT, of his team's work. "And we see that you can have a little bit of variation and still show superconductivity and other exotic physics, but it can’t be too much. We now have characterised how much twist variation you can have, and what is the degradation effect of having too much."

The researchers found that the sheets varied in local twist angle by as little as 1.1 degrees, but that the variation was enough to throw the material off its task: Structures with a narrower range of twist angles had more pronounced exotic properties compared to those whose angles varied through a wider range.

In a second, related, study, researchers created a twisted graphene structure with four layers rather than the usual two — and found it was more sensitive than its predecessor, and may allow for finer-grained control of its exotic properties.

“These two studies are aiming to better understand the puzzling physical behavior of magic-angle twistronics devices," says graduate student Yan Cao of the work. "Once understood, physicists believe these devices could help design and engineer a new generation of high-temperature superconductors, topological devices for quantum information processing, and low-energy technologies."

Both the imaging paper and the four-layer paper have been published in the journal Nature under closed-access terms.