In 2024, superconductivity—the flow of electric current with zero resistance—was discovered in three distinct materials. Two instances stretched the textbook understanding of the phenomenon, while the third defied it entirely. “It’s an extremely unusual form of superconductivity that a lot of people would have said is not possible,” said Ashvin Vishwanath, a physicist at Harvard University who was not involved in the discoveries.
Since 1911, when Dutch scientist Heike Kamerlingh Onnes first observed electrical resistance vanish, superconductivity has captivated physicists. The phenomenon's mystery lies in how it occurs: electrons, which naturally repel each other, must somehow pair up to create a superconducting state.
Superconductivity also holds immense technological promise. It has already led to innovations like MRI machines and particle colliders. If researchers could fully grasp how and when superconductivity arises, they might engineer wires that superconduct electricity under everyday conditions rather than requiring extreme cold. Such advancements could enable lossless power grids and magnetically levitating vehicles.
Recent discoveries have deepened the mystery of superconductivity while sparking new optimism. “It seems to be, in materials, that superconductivity is everywhere,” said Matthew Yankowitz, a physicist at the University of Washington.
These discoveries stem from advances in materials science. All three new cases of superconductivity arise in devices made from atom-thin sheets, which offer unprecedented flexibility. Physicists can switch these materials between conducting, insulating, and exotic behaviors, accelerating the search for superconductors.
Materials seem to pair electrons in different ways, much like how birds, bees, and dragonflies all achieve flight using different wing structures. While researchers debate the specific mechanisms in various two-dimensional materials, the growing diversity of superconductors may eventually offer a universal understanding of this phenomenon.
The case of Kamerlingh Onnes’ discovery—and similar findings in extremely cold metals—was explained in 1957. John Bardeen, Leon Cooper, and John Robert Schrieffer showed that, at low temperatures, a material's atomic lattice calms down, allowing subtle interactions to emerge. Electrons deform the lattice, creating a positive charge that attracts a second electron, forming a "Cooper pair." These pairs behave as a coherent quantum entity, slipping between the material’s atoms without resistance.
The theory earned Bardeen, Cooper, and Schrieffer the Nobel Prize in Physics in 1972 but did not fully explain all superconductors. In the 1980s, researchers discovered copper-based crystals called cuprates that superconduct at higher temperatures, defying the original theory.
In 2018, Pablo Jarillo-Herrero at MIT found that twisting two sheets of graphene—carbon atoms arranged in a honeycomb pattern—at precisely 1.1 degrees created a superconductor. Physicists could tune these materials by applying electric fields to reproduce behaviors of countless potential materials, including superconductivity in "magic angle" graphene.
This discovery spurred further research. Scientists found that even without twisting, three-layer graphene systems could superconduct.
In 2020, Cory Dean’s team at Columbia University detected possible superconductivity in a two-dimensional transition metal dichalcogenide (TMD) material by twisting sheets at a 5-degree angle. Although resistance initially dropped, the findings were inconclusive.
Liang Fu of MIT and Constantin Schrade of Louisiana State University proposed that the phenomenon was not driven by phonons but by the slow movement of electrons in a moiré pattern formed by the twist. This environment allowed electrons to collectively guide their behavior and pair up.
Dean’s group confirmed superconductivity in the TMD material in 2024, validating earlier theories. Researchers believe these discoveries mark only the beginning of uncovering the full potential of superconductivity across new materials and configurations.
Source: Wired. THE ORIGINAL VERSION of this story appeared in Quanta Magazine.
Image Credit: Mark Belan
