Solid hydrogen sulfide (H2S) has not previously been considered a superconductor because, upon metallization under pressure, it was believed to dissociate into its constituent elements. Recent theoretical work4 indicated that such dissociation would not occur and predicted that H2S pressurized at 1.6 million atmospheres would show superconductivity at temperatures above 80 K. This led to the practical work of Drozdov et al.,1 who found that H2S compressed in a diamond anvil cell exhibited two astonishing superconductive states at pressures above 1 million atmospheres: the superconductivity ranging from 30 to 150 K measured in the low-temperature runs (Fig. 1)1 relates to H2S, as it is consistent with calculations;4 the highest superconductivity of 203 K was achieved in samples annealed at the room temperature (Fig. 2).1 The transition temperature showed a pronounced isotope effect, indicating phonon-mediated superconductivity. The 203 K superconductivity is probably associated with a stoichiometric change to H3S that was predicted to be a high-temperature superconductor5 due to the decomposition of H2S under pressure.

The work by Drozdov et al.1 has disproved the conventional wisdom regarding the 40 K superconduction limit of phonon-mediated superconductors, and, more significantly, it supports the general idea of high-temperature superconductivity in hydrogen-rich materials. A broad range of hydrogen-rich materials is ready for exploration, and they offer the tantalizing prospect of the imminent development of room-temperature superconductors.