original version of this story appeared in Quanta MagazineE.
In 2024, superconductivity, the flow of electric current without resistance, was discovered in three different materials. Two examples extend the textbook’s understanding of the phenomenon. The third shreds it completely. “This is a very unusual type of superconductor that many people said was impossible,” he said. Ashvin VishwanathA physicist at Harvard University who was not involved in the discovery.
Superconductivity has captivated physicists since 1911, when Dutch scientist Heike Kamerlingh Onnes first observed the disappearance of electrical resistance. There is pure mystery as to how it happens. This phenomenon means that electrons that carry electric current must pair up. Electrons repel each other, so how can they combine?
Next is the technical outlook. Already, superconductivity has enabled the development of MRI machines and powerful particle colliders. If physicists could fully understand how and when this phenomenon occurs, perhaps they could design wires that superconduct electricity under everyday conditions, not just at low temperatures as they do today. World-changing technologies like lossless power grids and maglev vehicles may follow.
A flurry of recent discoveries has further complicated the mystery of superconductivity and heightened optimism. “Superconductivity seems to be ubiquitous in materials,” he said. Matthew JankowitzPhysicist at the University of Washington.
The discovery stems from a recent revolution in materials science. All three new examples of superconductivity arise from devices assembled from flat sheets of atoms. This material demonstrates unprecedented flexibility. Physicists can switch between conductive, insulating, and more exotic behavior at the touch of a button. This is modern alchemy, spurring the search for superconductors.
It now seems more and more likely that this phenomenon will occur due to a variety of causes. Just as birds, bees, and dragonflies all use different wing structures to fly, materials also appear to pair electrons in different ways. Even as researchers debate exactly what’s going on in the various two-dimensional materials in question, they hope their growing menagerie of superconductors will help achieve a more universal view of the fascinating phenomenon.
electronic pairing
Kamerlingh Onnes’ observations (and the case for superconductivity seen in other cryogenic metals) were finally broken in 1957. John Bardeen, Leon Cooper, and John Robert Schrieffer figured it out At low temperatures, the material’s restless atomic lattice quiets down, resulting in more delicate effects. The electrons gently tug on the protons in the lattice, pulling them inward, creating an excess positive charge. These modifications, known as phonons, can attract a second electron to form a “Cooper pair.” Cooper pairs can all come together as a cohesive quantum entity in a way that single elections cannot. The resulting quantum soup slides without friction between the atoms of the material, which would normally impede the flow of electricity.
Bardeen, Cooper, and Schrieffer’s theory of phonon-based superconductivity won the Nobel Prize in Physics in 1972. But it turns out that’s not all. In the 1980s, physicists discovered that copper-filled crystals called cuprates could produce superconductivity at higher temperatures, where atomic wobbles wash out phonons. Other similar examples followed.
