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Phoenix666 writes:

Singularity Hub:

Take two layers of graphene. Twist them so that they are at a very slight angle to each other—1.1 degrees, to be precise—and then stack them together. (This is easier said than done, as the idea was first proposed in 2007 but only realized in 2018.) The resulting bilayer graphene is a superconductor: when the temperature is dropped below a critical threshold, the material has no electrical resistance at all.

[...]The reasoning behind graphene’s “magic angle” arises due to the energy barrier for quantum tunnelling between the two layers of graphene. As you approach the precise angle of rotation (1.1 degrees), the energy barrier becomes very small, allowing electrons to strongly interact and become correlated between the layers. Fabricating this material wasn’t easy—it took the lab at MIT that discovered it several years to learn how to produce layers of graphene where the twist angle was this precisely controlled.

It was discovered that one of their test devices was a perfect insulator; it didn’t allow any electrons to be transmitted. Apply a small voltage, however, adding free electrons to the system, and there is a sudden transition to superconductivity. Once twisted bilayer graphene has been manufactured, its electronic and superconducting properties can be tuned simply by applying electrical fields or pressure to the layers.

The researchers have learned how to finely tune the properties of graphene to transform it from a perfect insulator to a superconductor.

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