A team of physicists led by Milan Allan of Ludwig Maximilian University of Munich and Ingmar Swart of Utrecht University has found some answers to the decades-old question of why cuprates superconduct at comparatively high temperatures, by listening to the faint electrical crackle of current flowing into the material.
The team's study was reported in Science. The pseudogap is a strange state central to the cuprate puzzle. "The pseudogap is a phenomenon of missing electrons," Allan said. Above the temperature at which cuprates become superconducting, some of their electrons seem to vanish: measurements find far fewer of them at the energies where they should be. "Everybody knows that from different probes, you see that there's these vanishing electrons, but nobody knows why," Allan said.
Superconductors carry electricity without resistance, but most only work a few degrees above absolute zero. In the late 1980s, copper-based materials called cuprates were found to superconduct at higher temperatures, reachable with affordable liquid nitrogen. Nearly 40 years later, physicists still do not agree on why.
Analysis
Why This Matters
- The pseudogap has defied explanation for nearly 40 years, and pinning down why its electrons vanish would answer a central question about how cuprate superconductors work.
- A settled theory of cuprates could point toward materials that superconduct at more practical temperatures, with implications for power grids, magnets and electronics.
- The team's method, capturing the faint electrical noise of current flowing into a material, offers a new way to observe quantum states that other probes see only indirectly.
Background
Superconductors carry electricity with zero resistance, but most require cooling to within a few degrees of absolute zero, which is expensive. The discovery of cuprates in the late 1980s raised that barrier to temperatures reachable with inexpensive liquid nitrogen, raising hopes of practical applications. Yet the mechanism behind their high-temperature superconductivity has never been settled. The pseudogap, a phase appearing just above the superconducting transition temperature in which electrons vanish from the energies where they should be, has long been considered key to the puzzle.
What to Watch
- The full explanation the team proposes for the vanished electrons in the published Science study.
- Whether other groups can reproduce the electrical-noise measurements in other cuprate compounds.
- Whether the findings settle the pseudogap debate or open the door to competing interpretations.
Checked
12 claims in this story checked against 1 source: 12 supported.
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- SupportedListening to electrical crackle has yielded some answers to the cuprate superconductor puzzle.Ars Technica - All content: “In a recent Science study, a team of physicists led by Milan Allan of Ludwig Maximilian University of Munich and Ingmar Swart of Utrecht University in the Netherlands has found some answers by listening to the faint electrical crackle of current flowing into a cuprate.”
- SupportedA Munich and Utrecht team probes the pseudogap, where electrons appear to vanish above the superconducting temperature.Ars Technica - All content: “Above the temperature at which cuprates become superconducting, some of their electrons seem to vanish”
- SupportedThe team is led by Milan Allan of Ludwig Maximilian University of Munich and Ingmar Swart of Utrecht University.Ars Technica - All content: “a team of physicists led by Milan Allan of Ludwig Maximilian University of Munich and Ingmar Swart of Utrecht University in the Netherlands”
- SupportedThe team found some answers to why cuprates superconduct at comparatively high temperatures by listening to faint electrical crackle.Ars Technica - All content: “has found some answers by listening to the faint electrical crackle of current flowing into a cuprate.”
- SupportedThe team's study was reported in Science.Ars Technica - All content: “In a recent Science study”
- SupportedThe pseudogap is a strange state central to the cuprate puzzle.Ars Technica - All content: “Central to the mystery of cuprates’ high-temperature superconductivity is a strange state called the pseudogap.”
- SupportedAllan said, “The pseudogap is a phenomenon of missing electrons.”Ars Technica - All content: ““The pseudogap is a phenomenon of missing electrons,” Allan said.”
- SupportedAbove the superconducting temperature, some cuprate electrons seem to vanish, with measurements finding fewer at the energies where they should be.Ars Technica - All content: “Above the temperature at which cuprates become superconducting, some of their electrons seem to vanish—measurements find far fewer of them at the energies where they should be.”
- SupportedAllan said, “Everybody knows that from different probes, you see that there's these vanishing electrons, but nobody knows why.”Ars Technica - All content: ““Everybody knows that from different probes, you see that there's these vanishing electrons, but nobody knows why,” Allan said.”
- SupportedSuperconductors carry electricity without resistance, and most work only a few degrees above absolute zero.Ars Technica - All content: “Superconductors carry electricity without resistance, but most only work a few degrees above absolute zero.”
- SupportedIn the late 1980s, copper-based materials called cuprates were found to superconduct at higher temperatures, reachable with affordable liquid nitrogen.Ars Technica - All content: “In the late 1980s, copper-based materials called cuprates were found to superconduct at higher temperatures—reachable with affordable liquid nitrogen.”
- SupportedNearly 40 years later, physicists still do not agree on why cuprates superconduct at higher temperatures.Ars Technica - All content: “Yet nearly 40 years later, physicists still don't agree on why.”
