A superconducting magnet is cooled by liquid nitrogen, producing a strong magnetic field that causes the magnet to levitate.Credit: Patrick Gaillardin/LookAt Sciences/SPL
A Korean team’s claim to have discovered a superconductor that works at room temperature and ambient pressure has become a viral sensation — and prompted a slew of replication efforts by scientists and amateurs alike. But initial efforts to experimentally and theoretically reproduce the buzzworthy result have come up short, and researchers remain deeply sceptical.
The research team, led by Sukbae Lee and Ji-Hoon Kim at the start-up firm Quantum Energy Research Centre in Seoul said in preprints published on 25 July1,2 that a compound of copper, lead, phosphorus and oxygen, dubbed LK-99, is a superconductor at ambient pressure and temperatures above 127 °C (400 Kelvin). The team claims that samples show two key signs of superconductivity: zero electrical resistance and the Meissner effect, in which the material expels magnetic fields, leading samples to levitate above a magnet. Previous efforts have achieved superconductivity only in certain materials under incredibly low temperatures or extremely high pressures. No material has ever been confirmed to be a superconductor under ambient conditions.
LK-99’s purported superconductivity drew immediate scrutiny from scientists. “My first impression was ‘no.’” says Inna Vishik, a condensed matter experimentalist at the University of California, Davis. “These ‘Unidentified Superconducting Objects’, as they’re sometimes called, reliably show up on the arXiv. There’s a new one every year or so.” Advances in superconductivity are often touted for their potential practical impact on technologies such as computer chips and maglev trains, but Vishik points out that such excitement might be misplaced. Historically, progress in superconductivity has had tremendous benefits for basic science, but little in the way of everyday applications. There’s no guarantee a material that is a room-temperature superconductor would be of practical use, Vishik says.
The first attempts to replicate LK-99, reported in the past days, have not improved the material’s prospects. None of the studies provide direct evidence for any superconductivity in the material. (The Korean team did not respond to Nature’s request for comment.)
Two separate experimental efforts by teams at the National Physical Laboratory of India in New Delhi3 and Beihang University in Beijing4, reported synthesizing LK-99, but did not observe signs of superconductivity. A third experiment by researchers at Southeast University in Nanjing5 found no Meissner effect, but measured near zero resistance in LK-99 at -163 °C (110 K) — which is far below room temperature, but high for superconductors.
Theorists have also entered the fray. Several theoretical studies6,7,8,9 used a com
