In a discovery that could reshape one of the most vigorous debates in modern condensed matter physics, researchers at the National Graphene Institute at the University of Manchester have shown that superconductivity in magic-angle twisted bilayer graphene can be completely switched off by screening the interactions between electrons. The finding, published in Physical Review X, delivers some of the strongest experimental evidence to date that the superconductivity in this celebrated material is driven not by lattice vibrations, as in conventional superconductors, but by the electrons themselves — a hallmark of what physicists call unconventional superconductivity.
Magic-angle twisted bilayer graphene has captivated the scientific community ever since its superconducting properties were first revealed. The material is fabricated by taking two atomically thin sheets of carbon atoms arranged in a honeycomb lattice and stacking them with a precise rotational twist of approximately 1.1 degrees. At this seemingly arbitrary angle, the electronic bands of the two layers flatten dramatically, electrons slow to a crawl, and interactions between them become overwhelmingly important. The result is a system that superconducts at temperatures only a few kelvin above absolute zero, yet behaves in ways that evoke the great unsolved mysteries of high-temperature superconductivity in cuprates and other exotic materials.
For nearly a decade, however, theorists have been split over what actually glues the electrons into the pairs that flow without resistance. Some propose that the pairing arises purely from collective electronic behavior — fluctuations and correlations among the electrons themselves. Others argue for a more mundane, conventional origin: phonons, the quantized vibrations of the atomic lattice, mediating the attractive interaction, much as they do in ordinary superconductors such as lead or niobium. Distinguishing between these scenarios experimentally has proven extraordinarily difficult, and a series of earlier screening experiments produced ambiguous, weaker results that left the debate simmering.
The Manchester-led team, which included collaborators from 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, found a way to break the deadlock. Dr Julien Barrier, the lead author of the study, describes the two critical hurdles that had to be overcome. “To make a difference, we had to solve two issues,” he explained. “First, to build a device in which the screening layer sits extremely close, a fraction of a nanometre, to the superconducting graphene while remaining electronically separate. Second, we had to make that screening layer tuneable. To this effect, we used a twisted graphene bilayer in atomic contact to the magic-angle graphene.”
The device architecture is a masterpiece of nanoscale engineering. It consists of two twisted graphene bilayers separated by less than a nanometre — a gap so small that it approaches the scale of individual atomic bonds — yet the two systems remain electronically decoupled. This means electrons cannot hop between the layers, but the electric fields they generate can. By adjusting the carrier density in the adjacent screening layer, the researchers could continuously tune the strength of the Coulomb interaction — the repulsive electrostatic force between electrons — experienced by the superconducting layer. The closer proximity and the tunability of the screening layer allowed modifications of Coulomb interactions over distances as short as 0.3 nanometres, an unprecedented level of control in such experiments.
What happened next surprised even the team. “When we switched on the screening, we were surprised to find that superconductivity was completely suppressed,” said Professor Alexey Berdyugin of the National University of Singapore, a corresponding author of the study. “This provides clear experimental evidence that superconductivity in this system originates from strong electron-electron interactions. This behaviour offers a new opportunity to better understand the mechanisms underlying superconductivity in other materials with strong electronic interactions, including high-temperature superconductors.”
The results were unambiguous and strikingly dose-dependent. As the researchers progressively increased the carrier density in the neighbouring graphene bilayer, the superconductivity in the adjacent magic-angle layer weakened steadily. At sufficiently high carrier densities, superconductivity vanished entirely. Moreover, the superconducting critical temperature — the temperature below which the material loses all electrical resistance — could be reduced by more than an order of magnitude through screening alone. Alongside the suppression of superconductivity, the team observed that correlated insulating states, another enigmatic signature of magic-angle graphene in which the interacting electrons lock themselves into an insulating arrangement, disappeared under the same conditions. The parallel fates of superconductivity and the correlated insulating states reinforce the picture that both phenomena spring from the same source: strong electronic correlations.
The theoretical implications are profound. If phonons — lattice vibrations — were the glue binding electron pairs, screening the Coulomb interaction would be expected to leave superconductivity largely unchanged or even to enhance it slightly, since screening suppresses the repulsive Coulomb interaction that normally opposes conventional pairing. The Manchester team observed precisely the opposite: screening destroyed the superconducting state. According to the researchers, this inverted response rules out conventional phonon-mediated pairing as an explanation for superconductivity in this class of materials. The enhanced magnitude of the effect, far stronger than in earlier screening experiments, is attributed to the exceptionally small separation between the superconducting and screening layers, which allowed the Coulomb interaction to be modified far more effectively than ever before.
Importantly, the authors are careful about what the study does and does not claim. While the work does not identify a single definitive pairing mechanism, several unconventional theories remain consistent with the results, including those based on collective electronic interactions, such as fluctuation-driven pairing channels. What the experiment does accomplish is to place much tighter constraints on any future theory that hopes to explain superconductivity in magic-angle graphene. Any candidate mechanism must now survive a brutal test: it must predict that superconductivity collapses when Coulomb interactions are screened at the nanometre scale. Theories relying primarily on conventional phonon glue no longer pass.
Professor Sir Andre Geim, the Nobel laureate who first isolated graphene and a corresponding author of the new work, frames the achievement in the context of physics’ grandest prize: superconductivity at room temperature. “Personally, I am interested only in high-temperature superconductivity — preferably at room temperature or above,” he said. “This study was done at temperatures so low that even helium turns liquid. But unless we understand what makes superconductivity work, we are unlikely ever to reach room-temperature superconductivity, let alone make this remarkable phenomenon commercially useful. Our study takes only a tiny step — but still a step — in that direction, helping to nail down the mechanism of exotic superconductivity in graphene. Rome was not built in a day.”
Geim’s caution is well-founded. Room-temperature superconductivity remains the holy grail of materials science, promising lossless power transmission, ultra-efficient magnets and transformational electronics. But the path there runs directly through the problem that this study addresses: understanding the mechanism of pairing in strongly correlated electron systems. Because magic-angle graphene is tunable, clean and theoretically tractable in ways that cuprates are not, it has become a Rosetta Stone of sorts for the physics of unconventional superconductors. Each experimental advance in decoding it reverberates through the broader effort to understand and eventually engineer higher-temperature superconductors.
Beyond superconductivity itself, the technique developed by the team may have far-reaching applications. “In this study, we introduced a method for screening electron-electron interactions over scales as short as 0.3 nm, which turned out to be crucial for controlling superconductivity in magic-angle graphene,” Professor Berdyugin concluded. “We anticipate that this unprecedented level of short-range screening could also help clarify many other debated phenomena.” Strongly correlated materials are riddled with contested phenomena — strange metals, nematicity, competing orders, quantum criticality — and a controllable, short-range knob for dialling electron interactions up and down could prove decisive in disentangling them.
The study stands as a vivid demonstration of how atomically engineered van der Waals heterostructures — stacks of two-dimensional materials assembled layer by layer with atomic precision — can answer questions that bulk crystals cannot. By placing a tuneable electronic screen within a fraction of a nanometre of a superconducting sheet without contaminating it, the Manchester-led collaboration has effectively performed a controlled experiment on the fundamental interaction behind one of nature’s most subtle collective states. The superconductivity in magic-angle graphene, the evidence now says, belongs to the electrons themselves. The next chapter — identifying exactly how they conspire to pair — is still to be written, but the rules of the game have just been redrawn.
Subject of Research: Superconductivity in magic-angle twisted bilayer graphene and its suppression through Coulomb screening, providing evidence for unconventional, interaction-driven superconductivity.
Subject of Research: Chemistry
Article Title: Coulomb Screening of Superconductivity in Magic-Angle Graphene
Article References: Barrier, J., et al. Coulomb Screening of Superconductivity in Magic-Angle Graphene. Physical Review X. https://journals.aps.org/prx/abstract/10.1103/z9qg-287y Original publication
Image Credits: AI Generated
DOI: Not provided
Keywords: magic-angle graphene, twisted bilayer graphene, unconventional superconductivity, Coulomb screening, electron-electron interactions, correlated insulating states, phonon-mediated pairing, National Graphene Institute, Physical Review X, van der Waals heterostructures, high-temperature superconductors
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Neil Sanderson. (September 5, 2026). Graphene research reveals evidence of unconventional superconductivity. Scienmag. https://scienmag.com/graphene-research-reveals-evidence-of-unconventional-superconductivity/
Neil Sanderson. “Graphene research reveals evidence of unconventional superconductivity.” Scienmag, 5 September 2026, https://scienmag.com/graphene-research-reveals-evidence-of-unconventional-superconductivity/. Accessed 5 September 2026.
Neil Sanderson. “Graphene research reveals evidence of unconventional superconductivity.” Scienmag. September 5, 2026. https://scienmag.com/graphene-research-reveals-evidence-of-unconventional-superconductivity/
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