X-ray Diffraction and Equation of State of the C-S-H Room-Temperature Superconductor

Abstract

X-ray diffraction indicates that the structure of the recently discovered room temperature carbonaceous sulfur hydride (C-S-H) superconductor is derived from previously established van der Waals compounds found in the H${}_2$S-H${}_2$ and CH${}_4$-H${}_2$ systems. Crystals of the superconducting phase were produced by a photochemical synthesis technique leading to the superconducting critical temperature $T_c$ of 288 K at 267 GPa. Single-crystal x-ray diffraction patterns measured from 124 to 178 GPa, within the pressure range of the superconducting phase, give an orthorhombic structure derived from the Al${}_2$Cu-type determined for (H${}_2$S)${}_2$H${}_2$ and (CH${}_4$)${}_2$H${}_2$ that differs from those predicted and observed for the S-H system to these pressures. The formation and stability of the C-S-H compound can be understood in terms of the close similarity in effective volumes of the H${}_2$S and CH${}_4$ components over a broad range of pressures. The relative amounts of carbon and sulfur in the structure is not determined, and denser carbon-bearing S-H structures may form at higher pressures. The results are consistent with hole-doping enhancement of $T_c$ by carbon proposed for the room-temperature superconductivity in this system.

8 pages, 6 figures

References in corpus (4)

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Cited by in corpus (8)

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• High-temperature superconductivity in hydrides
• Materials under high pressure: A chemical perspective
• Missing theoretical evidence for conventional room temperature superconductivity in low enthalpy structures of carbonaceous sulfur hydrides
• A Little Bit of Carbon Can do a Lot for Superconductivity in H${}_3$S
• Synthesis and structure of carbon doped H3S compounds at high pressure
• Enhanced superconductivity in C-S-H compounds at high pressure
• Superconducting $I$$\overline{4}$3$m$ CSH${}_7$ model applied to resistive transition temperature data for compressed C-S-H at high pressure