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By developing a novel technique to get a “direct view” of its properties, MIT physicists have reported a significant breakthrough, providing the most direct evidence to date of unconventional superconductivity in “magic-angle” twisted tri-layer graphene (MATTG). The discovery provides new confirmation that the material, composed of three stacked and twisted atom-thin carbon sheets, is a unique type of superconductor. This finding is a crucial step in the global search for room-temperature superconductors, often referred to as the “Holy Grail” of physics. “This direct view can reveal how electrons pair and compete with other states, paving the way to design and control new superconductors and quantum materials that could one day power more efficient technologies or quantum computers,” said co-lead author Jeong Min Park. While conventional superconductors are extremely energy-efficient, they only work at ultra-low temperatures, limiting their practical use. A superconductor that works at higher, more practical temperatures could revolutionize technology, enabling everything from zero-energy-loss power grids and practical quantum computers to more efficient MRI machines. Direct measurement of superconducting gap The research team’s breakthrough lies in their direct measurement of MATTG’s “superconducting gap”—a property describing the resilience of its superconducting state. They discovered that this gap has a distinct V-shaped profile, which is fundamentally different from the flat, uniform gap found in conventional superconductors. This difference confirms that the mechanism causing superconductivity in MATTG must also be unconventional. Novel experimental platform To achieve this, the researchers developed a novel experimental platform. “The new technique combines electron tunneling with electrical transport — a technique that is used to gauge a material’s superconductivity, by sending current through and continuously measuring its electrical resistance (zero resistance signals that a material is superconducting),” added the team in a press release. This combination allowed the team to unambiguously link the V-shaped gap directly to the material’s superconductivity. “The superconducting gap gives us a clue to what kind of mechanism can lead to things like room-temperature superconductors that will eventually benefit human society,” said Shuwen Sun, study co-lead author and a graduate student in MIT’s Department of Physics. Distinct pairing mechanism and future work Superconductivity occurs when electrons “pair up” into “Cooper pairs” and glide through a material without friction or energy loss. In conventional superconductors, these pairs are weakly bound and formed through vibrations in the atomic lattice. Researchers suspect the pairing mechanism in MATTG is different. Park remarked that the pairing “likely arises from strong electronic interactions rather than lattice vibrations,” meaning the electrons themselves “help each other pair up.” MATTG is part of a new class of materials studied in “twistronics,” a field pioneered by the study’s senior author, MIT professor Pablo Jarillo-Herrero. His group first produced magic-angle graphene in 2018, revealing that stacking 2D materials at specific angles could induce exotic electronic behaviors. The team plans to utilize their new experimental platform to investigate other twisted 2D materials, aiming to identify new candidates for future technologies. “Understanding one unconventional superconductor very well may trigger our understanding of the rest,” concluded Jarillo-Herrero. “This understanding may guide the design of superconductors that work at room temperature, for example, which is sort of the Holy Grail of the entire field.” The study has been published in the journal Science.
