Scientists from India report that pure Bismuth - a semimetal with a very low number of electrons per given volume, or carrier concentration - is superconducting at ultralow temperatures. The observation makes Bismuth one of the two lowest carrier density superconductors to date. At low temperatures, many elemental metals, such as lead or aluminum, transition to being superconducting - a state in which electric current passing through these materials can persist indefinitely with no power source. In Bismuth, a single electron is shared by 100,000 atoms, making this semimetal's carrier density quite low, which has made it seem unlikely it could be a superconductor. In fact, Bismuth has been shown to resist superconductivity all the way down to super-cold temperatures of 10 millikelvin. Here, Om Prakash and colleagues perform magnetization measurements to show that the superconducting transition does occur in pure bulk Bismuth at 0.5 millikelvin. They report the observation in pure Bismuth single crystals that they prepared. Because Bismuth doesn't fit neatly into the standard picture of superconductivity, the authors say, further theoretical work is necessary to fully explain the findings.
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Journal
Science