https://news.mit.edu/2022/superconducting-graphene-family-0708 Skip to content | Massachusetts Institute of Technology MIT Top Menu| * Education * Research * Innovation * Admissions + Aid * Campus Life * News * Alumni * About MIT * More | Search MIT Search websites, locations, and people [ ] See More Results Suggestions or feedback? MIT News | Massachusetts Institute of Technology Subscribe to MIT News newsletter Browse Enter keywords to search for news articles: [ ] Submit Browse By Topics View All - Explore: * Machine learning * Social justice * Startups * Black holes * Classes and programs Departments View All - Explore: * Aeronautics and Astronautics * Brain and Cognitive Sciences * Architecture * Political Science * Mechanical Engineering Centers, Labs, & Programs View All - Explore: * Abdul Latif Jameel Poverty Action Lab (J-PAL) * Picower Institute for Learning and Memory * Media Lab * Lincoln Laboratory Schools * School of Architecture + Planning * School of Engineering * School of Humanities, Arts, and Social Sciences * Sloan School of Management * School of Science * MIT Schwarzman College of Computing View all news coverage of MIT in the media - Subscribe to MIT newsletter - Close Breadcrumb 1. MIT News 2. Physicists discover a "family" of robust, superconducting graphene structures Physicists discover a "family" of robust, superconducting graphene structures The findings could inform the design of practical superconducting devices. Jennifer Chu | MIT News Office Publication Date: July 8, 2022 Press Inquiries Press Contact: Abby Abazorius Email: abbya@mit.edu Phone: 617-253-2709 MIT News Office Media Download Cooper pairs in magic-angle multilayer graphene | Download Image Caption: An illustration showing superconducting Cooper pairs in magic-angle multilayer graphene family. The adjacent layers are twisted in an alternating fashion. Credits: Credit: Ella Maru Studio graphic showing 2D layers of graphene | Download Image Caption: MIT physicists have established twisted graphene as a new "family" of robust superconductors, each member consisting of alternating graphene layers, stacked at precise angles. Credits: Courtesy of the researchers *Terms of Use: Images for download on the MIT News office website are made available to non-commercial entities, press and the general public under a Creative Commons Attribution Non-Commercial No Derivatives license. You may not alter the images provided, other than to crop them to size. A credit line must be used when reproducing images; if one is not provided below, credit the images to "MIT." Close Cooper pairs in magic-angle multilayer graphene Caption: An illustration showing superconducting Cooper pairs in magic-angle multilayer graphene family. The adjacent layers are twisted in an alternating fashion. Credits: Credit: Ella Maru Studio graphic showing 2D layers of graphene Caption: MIT physicists have established twisted graphene as a new "family" of robust superconductors, each member consisting of alternating graphene layers, stacked at precise angles. Credits: Courtesy of the researchers Previous image Next image When it comes to graphene, it appears that superconductivity runs in the family. Graphene is a single-atom-thin material that can be exfoliated from the same graphite that is found in pencil lead. The ultrathin material is made entirely from carbon atoms that are arranged in a simple hexagonal pattern, similar to that of chicken wire. Since its isolation in 2004, graphene has been found to embody numerous remarkable properties in its single-layer form. In 2018, MIT researchers found that if two graphene layers are stacked at a very specific "magic" angle, the twisted bilayer structure could exhibit robust superconductivity, a widely sought material state in which an electrical current can flow through with zero energy loss. Recently, the same group found a similar superconductive state exists in twisted trilayer graphene -- a structure made from three graphene layers stacked at a precise, new magic angle. Now the team reports that -- you guessed it -- four and five graphene layers can be twisted and stacked at new magic angles to elicit robust superconductivity at low temperatures. This latest discovery, published this week in Nature Materials, establishes the various twisted and stacked configurations of graphene as the first known "family" of multilayer magic-angle superconductors. The team also identified similarities and differences between graphene family members. The findings could serve as a blueprint for designing practical, room-temperature superconductors. If the properties among family members could be replicated in other, naturally conductive materials, they could be harnessed, for instance, to deliver electricity without dissipation or build magnetically levitating trains that run without friction. "The magic-angle graphene system is now a legitimate 'family,' beyond a couple of systems," says lead author Jeong Min (Jane) Park, a graduate student in MIT's Department of Physics. "Having this family is particularly meaningful because it provides a way to design robust superconductors." Park's MIT co-authors include Yuan Cao, Li-Qiao Xia, Shuwen Sun, and Pablo Jarillo-Herrero, the Cecil and Ida Green Professor of Physics, along with Kenji Watanabe and Takashi Taniguchi of the National Institute for Materials Science in Tsukuba, Japan. "No limit" Jarillo-Herrero's group was the first to discover magic-angle graphene, in the form of a bilayer structure of two graphene sheets placed one atop the other and slightly offset at a precise angle of 1.1 degrees. This twisted configuration, known as a moire superlattice, transformed the material into a strong and persistent superconductor at ultralow temperatures. The researchers also found that the material exhibited a type of electronic structure known as a "flat band," in which the material's electrons have the same energy, regardless of their momentum. In this flat band state, and at ultracold temperatures, the normally frenetic electrons collectively slow down enough to pair up in what are known as Cooper pairs -- essential ingredients of superconductivity that can flow through the material without resistance. While the researchers observed that twisted bilayer graphene exhibited both superconductivity and a flat band structure, it wasn't clear whether the former arose from the latter. "There was no proof a flat band structure led to superconductivity," Park says. "Other groups since then have produced other twisted structures from other materials that have some flattish band, but they didn't really have robust superconductivity. So we wondered: Could we produce another flat band superconducting device?" As they considered this question, a group from Harvard University derived calculations that confirmed mathematically that three graphene layers, twisted at 1.6 degrees, would exhibit also flat bands, and suggested they may superconduct. They went on to show there should be no limit to the number of graphene layers that exhibit superconductivity, if stacked and twisted in just the right way, at angles they also predicted. Finally, they proved they could mathematically relate every multilayer structure to a common flat band structure -- strong proof that a flat band may lead to robust superconductivity. "They worked out there may be this entire hierarchy of graphene structures, to infinite layers, that might correspond to a similar mathematical expression for a flat band structure," Park says. Shortly after that work, Jarillo-Herrero's group found that, indeed, superconductivity and a flat band emerged in twisted trilayer graphene -- three graphene sheets, stacked like a cheese sandwich, the middle cheese layer shifted by 1.6 degrees with respect to the sandwiched outer layers. But the trilayer structure also showed subtle differences compared to its bilayer counterpart. "That made us ask, where do these two structures fit in terms of the whole class of materials, and are they from the same family?" Park says. An unconventional family In the current study, the team looked to level up the number of graphene layers. They fabricated two new structures, made from four and five graphene layers, respectively. Each structure is stacked alternately, similar to the shifted cheese sandwich of twisted trilayer graphene. The team kept the structures in a refrigerator below 1 kelvin (about -273 degrees Celsius), ran electrical current through each structure, and measured the output under various conditions, similar to tests for their bilayer and trilayer systems. Overall, they found that both four- and five-layer twisted graphene also exhibit robust superconductivity and a flat band. The structures also shared other similarities with their three-layer counterpart, such as their response under a magnetic field of varying strength, angle, and orientation. These experiments showed that twisted graphene structures could be considered a new family, or class of common superconducting materials. The experiments also suggested there may be a black sheep in the family: The original twisted bilayer structure, while sharing key properties, also showed subtle differences from its siblings. For instance, the group's previous experiments showed the structure's superconductivity broke down under lower magnetic fields and was more uneven as the field rotated, compared to its multilayer siblings. The team carried out simulations of each structure type, seeking an explanation for the differences between family members. They concluded that the fact that twisted bilayer graphene's superconductivity dies out under certain magnetic conditions is simply because all of its physical layers exist in a "nonmirrored" form within the structure. In other words, there are no two layers in the structure that are mirror opposites of each other, whereas graphene's multilayer siblings exhibit some sort of mirror symmetry. These findings suggest that the mechanism driving electrons to flow in a robust superconductive state is the same across the twisted graphene family. "That's quite important," Park notes. "Without knowing this, people might think bilayer graphene is more conventional compared to multilayer structures. But we show that this entire family may be unconventional, robust superconductors." This research was supported, in part, by the U.S. Department of Energy, the National Science Foundation, the Air Force Office of Scientific Research, the Gordon and Betty Moore Fundation, the Ramon Areces Foundation, and the CIFAR Program on Quantum Materials. Share this news article on: * Twitter * Facebook * LinkedIn * Reddit * Print Paper Paper: "Robust Superconductivity in Magic-Angle Multilayer Graphene Family" Related Links * Jarillo-Herrero group * MIT Center for Quantum Engineering * Department of Physics * School of Science Related Topics * Carbon * Electronics * Graphene * Physics * Nanoscience and nanotechnology * Superconductors * Quantum computing * Research * School of Science * National Science Foundation (NSF) Related Articles electron and photon graphic in graphene Physicists find direct evidence of strong electron correlation in a 2D material for the first time magic-angle twisted trilayer graphene "Magic-angle" trilayer graphene may be a rare, magnet-proof superconductor Illustration of electrons against hexagonal pattern Physicists create tunable superconductivity in twisted graphene "nanosandwich" In this illustration, two sheets of graphene are stacked together at a slightly offset "magic" angle, which can become either an insulator or superconductor. "We placed one sheet of graphene on top of another, similar to placing plastic wrap on top of plastic wrap," MIT professor Pablo Jarillo-Herrero says. "You would expect there would be wrinkles, and regions where the two sheets would... Researchers map tiny twists in "magic-angle" graphene Physicists at MIT and Harvard University have found that graphene, a lacy, honeycomb-like sheet of carbon atoms, can behave at two electrical extremes: as an insulator, in which electrons are completely blocked from flowing; and as a superconductor, in which electrical current can stream through without resistance. Insulator or superconductor? Physicists find graphene is both Previous item Next item More MIT News Headshots of Roderick Bayliss III, David Li, Syamantak Payra, Scott Barrow Moroch, and Alexander Cohen Five with MIT ties win 2022 Hertz Foundation Fellowships Award provides five years of funding and access to a community of innovative scholars and leaders in science and technology. Read full story - books laid out to read "MIT" Summer 2022 recommended reading from MIT Enjoy these recent titles from Institute faculty and staff. Read full story - Photo of Octavian-Eugen Ganea, wearing a ski jacket and climbing ropes, standing high up on a mountain with another mountain peak behind him Remembering Octavian-Eugen Ganea, a gifted MIT postdoc AI researcher and beloved colleague The brilliant scientist was known for both the depth of his intellect and his kindness. Read full story - map of lunar south pole Porosity of the moon's crust reveals bombardment history The moon sustained twice as many impacts as can be seen on its surface, scientists find. Read full story - a sock made from the novel fabrication process Smart textiles sense how their users are moving Researchers develop a comfortable, form-fitting fabric that recognizes its wearer's activities, like walking, running, and jumping. Read full story - Photo of a man and woman working in hexagonal raised flower beds in a grassy area of the MIT campus while two other people lounge in the background Charting the landscape at MIT After 48 years with the Institute, Manager of Grounds Services Norman Magnuson reflects on his role in a changing campus and profession. Read full story - * More news on MIT News homepage - More about MIT News at Massachusetts Institute of Technology This website is managed by the MIT News Office, part of the MIT Office of Communications. News by Schools/College: * School of Architecture and Planning * School of Engineering * School of Humanities, Arts, and Social Sciences * MIT Sloan School of Management * School of Science * MIT Schwarzman College of Computing Resources: * About the MIT News Office * MIT News Press Center * Terms of Use * Press Inquiries * Filming Guidelines * RSS Feeds Tools: * Subscribe to MIT Daily/Weekly * Subscribe to press releases * Submit campus news Massachusetts Institute of Technology MIT Top Level Links: * Education * Research * Innovation * Admissions + Aid * Campus Life * News * Alumni * About MIT * Join us in building a better world. Massachusetts Institute of Technology 77 Massachusetts Avenue, Cambridge, MA, USA Recommended Links: * Visit * Map (opens in new window) * Events (opens in new window) * People (opens in new window) * Careers (opens in new window) * Contact * Privacy * Accessibility * + Social Media Hub + MIT on Twitter + MIT on Facebook + MIT on YouTube + MIT on Instagram