A Boosted Critical Temperature of 166 K in Superconducting D3 S Synthesized from Elemental Sulfur and Hydrogen.

The discovery of superconductivity in H3 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 (Tc ). 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 Tc was determined correctly for samples prepared from compressed H2 S, since they are inevitably contaminated with H-depleted byproducts. Here, we prepare stoichiometric H3 S by direct in situ synthesis from elemental S and excess H2 . The Im 3 ‾ m phase of D3 S samples exhibits a Tc significantly higher than previously reported values (ca. 150 K), reaching a maximum Tc of 166 K at 157 GPa. Furthermore, we confirm that the sharp decrease in Tc below 150 GPa is accompanied by continuous rhombohedral structural distortions and demonstrate that the Cccm phase is non-metallic, with molecular H2 units in the crystal structure.