Superconductivity in an alloy with quasicrystal structure
Extraordinary things happen at low temperatures. One of the best examples is surely superconductivity. This phenomenon, wherein the electrical resistance of a solid drops to zero below a critical temperature, has been known for a century, and now has applications in science and industry. Physics and chemistry students can even make their own levitating magnets from superconducting alloys.
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Most superconductors, like most solids, are crystalline: their atomic structures are built from periodically repeating cells. Since the 1980s an alternative form of solid, the quasicrystal (QC), has become prominent. Although QCs have symmetry, like crystals, they have no repeat units. This lack of periodicity results in unusual electronic structures. Now, in a study in Nature Communications, a research team led by Nagoya University has discovered superconductivity in a QC for the first time.
The team studied an alloy of aluminum, zinc and magnesium. The crystalline version is known to be superconducting. However, the structure of Al-Zn-Mg depends on the ratio of the three elements. The team found that Al had a crucial effect on the alloy’s properties. As study first author Keisuke Kamiya notes, “When we reduced the Al content while keeping the Mg content almost constant, the critical temperature for superconductivity at first decreased gradually from ~0.8 to ~0.2 K. However, at 15% Al, two things happened: the alloy transformed into a quasicrystal, and the critical temperature plummeted to ~0.05 K.”
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