Crystal structures and promising superconductivity in Sc–S system under high pressure

In this work, we performed systematic simulations on the crystal structures and electronic properties of Sc-S crystalline system at a pressure range of 0-200 GPa. Our results reveal several stable stoichiometries, such as ScS₃, ScS₂, Sc₂S, and Sc₃S. The further electron-phonon simulations indicate that Sc₃S exhibits a superconducting critical temperature (<i>T</i>_c) of approximately 25 K at 200 GPa. Our in-depth analysis shows that such electron-phonon coupling (EPC) is primarily mediated by the Sc phonons in the mid-frequency region and the Sc 3<i>d</i>electrons at the Fermi level. Besides, in Sc₃S₄, the<i>T</i>_cexhibits a monotonic increase with electron doping, reaching a maximum of 10.4 K at a doping level of -0.5 <i>e</i>/cell at 20 GPa. The<i>T</i>_cenhancement upon doping arises from increased electronic density of states at the Fermi level and the strengthened low-frequency EPC. Our current findings not only offer insights into the exploration of new superconducting sulfides but also provide a direction for future experimental investigations of Sc-S system under high pressure.