Magic-angle graphene provides evidence for unconventional superconductivity

Researchers from The University of Manchester have discovered that superconductivity in a special type of graphene called magic-angle graphene can be completely switched off by controlling electron interactions. This finding, published in Physical Review X, provides strong evidence that electron interactions play a central role in superconductivity and helps resolve a long-standing debate about its origin.

Magic-angle graphene, created by stacking two sheets of graphene at a specific angle, has been the subject of intense study due to its unique properties. In the new research, scientists developed a graphene device with two twisted bilayers separated by less than a nanometer, allowing them to control electron interactions more effectively than in previous experiments.

By introducing a tunable screening layer in close proximity to the superconducting graphene, the team was able to completely suppress superconductivity when the screening interactions were strong. This finding suggests that conventional mechanisms involving lattice vibrations are unlikely to be responsible for superconductivity in magic-angle graphene.

Instead, the researchers propose that unconventional theories based on collective electronic interactions could explain the phenomenon. The study also found that increasing the carrier density in the neighboring graphene bilayer progressively weakened superconductivity in the adjacent magic-angle graphene, with superconductivity being completely suppressed at sufficiently high carrier densities.

These findings provide crucial insights into the mechanisms underlying superconductivity in strong electronic interaction materials and offer a new approach to understanding high-temperature superconductors.