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 (T_c ). 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_c 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 $$ m phase of D₃ S samples exhibits a T_c significantly higher than previously reported values (ca. 150 K), reaching a maximum T_c of 166 K at 157 GPa. Furthermore, we confirm that the sharp decrease in T_c 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.