A Boosted Critical Temperature of 166 K in Superconducting D S Synthesized from Elemental Sulfur and Hydrogen.

The discovery of superconductivity in H S at 203 K marked an advance towards room-temperature superconductivity and demonstrated the potential of H-dominated compounds to possess a high critical temperature (T ). There have been numerous reports of the H-S system over the last five years, but important questions remain unanswered. It is crucial to verify whether the T was determined correctly for samples prepared from compressed H S, since they are inevitably contaminated with H-depleted byproducts. Here, we prepare stoichiometric H S by direct in situ synthesis from elemental S and excess H . The Im m phase of D S samples exhibits a T significantly higher than previously reported values (ca. 150 K), reaching a maximum T of 166 K at 157 GPa. Furthermore, we confirm that the sharp decrease in T below 150 GPa is accompanied by continuous rhombohedral structural distortions and demonstrate that the Cccm phase is non-metallic, with molecular H units in the crystal structure.