In late 2014 the condensed-matter community was abuzz with news that Mikhail Eremets and his colleagues at the Max Planck Institute for Chemistry in Germany had discovered that hydrogen sulfide superconducts at 190 K when squeezed to a pressure of 150 GPa. Not only did the superconducting temperature shatter the previous record by 30 K, it’s nearly 10 K higher than the coldest temperature ever measured on Earth’s surface. Intriguingly, the record-breaking superconductor is of the conventional variety described by the venerable Bardeen-Cooper-Schrieffer theory, in contrast to cuprate and iron-based superconductors, whose superconducting mechanism continues to elude researchers. Eremets and his colleagues, aware that H2S likely couldn’t withstand the high pressures used in their experiments, suspected that their superconductor was a different hydride left from the dissociation of H2S. Independently, Tian Cui and his team at Jilin University in China had suggested that H3S should harbor superconductivity around 200 K at 200 GPa. Now Eremets’s group has teamed up with Katsuya Shimizu and colleagues at Osaka University to perform simultaneous resistance and x-ray diffraction measurements that confirm the theorists’ predictions. As shown in the figure, the diffraction pattern, measured at Japan’s SPring-8 synchrotron facility, contains the signatures of H3S (orange) and elemental sulfur (green), the other dissociation product. The inset shows the H3S crystal structure (yellow sulfur and blue hydrogen), which was also predicted by theory. The results raise hopes that theory can guide future searches for new high-temperature superconductors. (M. Einaga et al., Nat. Phys., in press, doi:10.1038/nphys3760.)
