Resistance is futile


“It is phenomenologically different from all other superconductors,” said Long Ju of MIT, leader of the group that found it. And that’s “comparing it to any superconductor that has been discovered since Kamerlingh Onnes in 1911.”

Twisting is too messy for Ju’s tastes; the moiré patterns tend to get disrupted by wrinkles in the sheets that make every device a little different. Instead, he studies a staircase-like arrangement of four graphene layers that can also slow electrons down. 

The challenge is to spot which graphene flakes naturally have this staircase arrangement —something Ju accomplishes with the aid of an infrared camera. “You don’t need to pick up four different layers and stack them,” Ju said. “Nature does it for you. You just need to have the right pair of eyes to see them.”

Last year, Ju’s group made a splash when they placed a five-layer graphene flake on an insulator at a twisted angle and observed a rare electron behavior that normally requires a strong magnetic field to induce. 

Theorists questioned whether the twist was essential, so he and his team went back to see what would happen when they took the twist out. “We found something that was more bizarre,” Ju said.

As they changed the strength of the electric field that they applied to the material, they found several settings where resistance vanished. 

In two cases, the superconductivity flickered, with resistance coming and going. 

Strangely, when they switched on a nearby magnet, the flickering stopped. Magnets normally kill superconductivity, but here, they strengthened it. “This existed only in the imagination of theorists,” Ju said. 



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