Hydrogen sulfide (H2S) is the noxious byproduct of anaerobic digestion that gives swamps their characteristic smell. In 2014 Mikhail Eremets of the Max Planck Institute for Chemistry and his colleagues set out to test a prediction of pressure-induced metallization and superconductivity in the malodorous compound.1
At a pressure of 100 GPa, the Max Planck group observed the hoped-for disappearance of resistance on cooling their sample below 60 K. But when they further raised the pressure to 150 GPa, the superconducting transition temperature Tc, instead of dropping as theory predicted, shot up to 190 K. Not only had the researchers shattered the previous record for Tc, held by a cuprate superconductor, by 30 K, but they had done so with a conventional phonon-mediated superconductor.
News of the group’s discovery set off a flurry of theoretical work to explain the finding.2 In the meantime,...
