Superconductivity determined by the S-H framework in CH4-inserted S-H framework hydrides under high pressures

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Chemistry

Background:

• The pursuit of room-temperature superconductors is a significant challenge in materials science.
• Carbonaceous sulfur hydrides (C-S-H) have emerged as potential candidates for high-temperature superconductivity.
• Previous studies suggested superconductivity in C-S-H systems around 270 GPa.

Purpose of the Study:

• To systematically investigate the structural properties and superconducting nature of C-S-H compounds under high pressure.
• To identify novel metastable stoichiometries and predict their superconducting transition temperatures (Tc).
• To understand the underlying mechanisms responsible for high Tc in these materials.

Main Methods:

• Extensive structure search using first-principles calculations.
• High-pressure simulations to determine stable and metastable phases.
• Electron-phonon coupling calculations to predict superconducting properties.

Main Results:

• Discovery of metastable C-S-H stoichiometries: CSH7, C2SH14, CS2H10, and CS2H11.
• Prediction of phonon-mediated superconductivity in several C-S-H phases (e.g., R3m-CSH7, Cm-CSH7) with Tc up to 130 K at 270 GPa.
• Identification of the sulfur-hydrogen (S-H) framework's crucial role in high Tc, with CH4 units suppressing superconductivity.

Conclusions:

• Metastable carbonaceous sulfur hydrides exhibit promising superconducting properties.
• The S-H framework is vital for achieving high Tc, while CH4 incorporation can reduce it.
• These findings offer guidance for designing and optimizing novel high-Tc superconductors.