Structural and Superconducting Parameters of Highly Compressed Sulfur

Abstract Recent pioneering experimental developments in measuring the superconducting energy gap Δ ( T ) in compressed sulfur using tunneling spectroscopy (Du et al., Phys. Rev. Lett. 133, 036002 (2024)) initiate an interest in better understanding the real atomic structure and superconducting properties of this element at high pressure. Here, available experimental data on highly compressed sulfur are analyzed, and, from the Δ ( T ) data reported by Du et al. (2024), the specific heat jump at the transition temperature is extracted. For a better understanding of materials structure at high pressure, here we propose a new approach that is the X‐ray diffraction size‐strain mappping of a sample in a diamond anvil cell. These size‐strain maps are revealed for pressurized sulfur herein. Finally, it is found that the Debye temperature Θ D and the electron‐phonon coupling constant λ e‐ph , which are extracted from the temperature‐dependent resistance reported by three independent research groups, are in excellent agreement with each other. The results show that superconducting sulfur exhibits a moderate level of nonadiabaticity, 0.04 ≤ Θ D / T F ≤ 0.20 (where T F is the Fermi temperature), which is similar to MgB 2 , pnictides, cuprates, La 4 H 23 , ThH 9 , H 3 S, LaBeH 8 , and LaH 10 .