This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers have completely suppressed superconductivity in magic-angle graphene by screening interactions between electrons, helping resolve a long-running debate about the origin of the phenomenon. Scientists from the National Graphene Institute at The University of Manchester have demonstrated that superconductivity in magic-angle graphene can be completely switched off by screening interactions between electrons.
The finding provides strong evidence that electron interactions play a central role in the phenomenon and helps address a key question that has remained unresolved since superconductivity was first discovered in the material. Magic-angle twisted bilayer graphene, created by stacking two sheets of graphene with a rotational offset of approximately 1.1 degrees, has become one of the most intensely studied quantum materials over the past decade. However, researchers have continued to debate what causes its superconductivity.
While some theories propose that electrons themselves drive the pairing responsible for superconductivity, others suggest a more conventional mechanism involving vibrations of the atomic lattice. In the new study, published in the journal Physical Review X, researchers developed a graphene device containing two twisted graphene bilayers separated by less than a nanometer while remaining electronically decoupled. This design enabled the team to control Coulomb screening more effectively than in previous experiments and directly test how superconductivity responds when electron interactions are weakened.
The research involved scientists from The University of Manchester, the National Graphene Institute, the Henry Royce Institute, Washington University in St. Louis, the University of Pennsylvania, the University of Antwerp, Japan's National Institute for Materials Science and the National University of Singapore. Julien Barrier, the lead author of the study, explained, "To make a difference, we had to solve two issues.
First, to build a device in which the screening layer sits extremely close—a fraction of a nanometer—from the superconducting graphene while remaining electronically separate. Second, we had to make that screening layer tunable. To this effect, we used a twisted graphene bilayer in atomic contact to the magic-angle graphene." Professor Alexey Berdyugin from the National University of Singapore, the corresponding author of this study, said, "When we switched on the screening, we were surprised to find that superconductivity was completely suppressed.
This provides clear experimental evidence that superconductivity in this system originates from strong electron-electron interactions. This behavior offers a new opportunity to better understand the mechanisms underlying superconductivity in other materials with strong electronic interactions, including high-temperature superconductors." Professor Sir Andre Geim, the corresponding author of this work, said, "Personally, I am interested only in high-temperature superconductivity—preferably at room temperature or above. This study was done at temperatures so low that even helium turns liquid.
Extract — continue reading at the source.
