A Boosted Critical Temperature of 166 K in Superconducting D3S Synthesized from Elemental Sulfur and Hydrogen

Abstract

The discovery of superconductivity in H3S 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 H2S, since they are inevitably contaminated with H-depleted byproducts. Here, we prepare stoichiometric H3S by direct in situ synthesis from elemental S and excess H2. The Im (Formula presented.) m phase of D3S 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.