Compressed Sr superconducting transition temperature up to 17.65 K

Due to the simplicity of their composition, the study of the superconducting properties of elemental substances holds significant importance for understanding the mechanisms of high-temperature superconductivity. This work involves simulated calculations to investigate the phase transition sequence and superconducting properties of Sr under pressure. The stability range of the Sr-IV phase C2/c was redefined, determining that it can extend up to 150 GPa, and the phase transition sequence of Sr under high pressure was studied. It was discovered that the d-electrons in the Sr-IV phase significantly contribute to the Fermi surface, a phenomenon closely related to the Van Hove singularity (VHS) near the saddle points. The increase in T_c of Sr under pressure is attributed to phonon softening and strong coupling resulting from the gradual overlap of VHS with the Fermi level, which is associated with the incomplete saturation of s-d electron transfer. Ultimately, the T_c of Sr reaches 17.65 K at 150 GPa, with a λ value of 1.26. This strong EPC is contributed by the interaction between d-electrons and medium-high-frequency phonons. This study extends new pathways for investigating the superconductivity of high-pressure phases of Sr and provides new insights for the theoretical study of elemental superconductors.