High-temperature superconductivity in sulfur hydride evidenced by alternating-current magnetic susceptibility

The search for high-temperature superconductivity is one of the research frontiers in physics. In the sulfur hydride system, an extremely high T _c (∼200 K) has been recently developed at pressure. However, the Meissner effect measurement above megabar pressures is still a great challenge. Here, we report the superconductivity identification of sulfur hydride at pressure, employing an in situ alternating-current magnetic susceptibility technique. We determine the superconducting phase diagram, finding that superconductivity suddenly appears at 117 GPa and T _c reaches 183 K at 149 GPa before decreasing monotonically with increasing pressure. By means of theoretical calculations, we elucidate the variation of T _c in the low-pressure region in terms of the changing stoichiometry of sulfur hydride and the further decrease in T _c owing to a drop in the electron-phonon interaction parameter λ. This work provides a new insight into clarifying superconducting phenomena and anchoring the superconducting phase diagram in the hydrides.