Enhanced superconductivity in C-S-H compounds at high pressure

TL;DR

This study uses first-principles calculations to identify new C-S-H structures with high-pressure superconductivity, revealing how sulfur addition enhances Tc and suggesting optimal molar ratios for higher transition temperatures.

Contribution

The paper introduces new stable C-S-H structures and elucidates how sulfur influences superconductivity, providing insights into optimizing high-pressure superconducting materials.

Findings

C2S2H4 becomes metallic and superconducting at 64 GPa with Tc up to 16.5 K at 300 GPa.

C2S3H4 exhibits a higher Tc of 47.4 K at 300 GPa due to sulfur-induced bond modifications.

Lowering the C:S molar ratio may further increase the superconducting transition temperature.

Abstract

Recently, the superconducting transition temperature Tc = 287 K has been experimentally obtained in the material composed of carbon, sulfur, and hydrogen under the high pressure of 267 GPa. The material structure is unknown yet, where the carbon and sulfur were added at a molar ratio of 1:1. Here, fixing the molar ratio of C : S = 1:1, we studied several possible C-S-H structures, and found a new stable structure C2S2H4 using the first-principles calculations. The C2S2H4 shows an insulator-to-metal transition and the superconducting ground state at the pressure of 64 GPa, and its Tc can reach 16.5 K at 300 GPa. In addition, we found another stable structure of C2S3H4, whose Tc is 47.4 K at 300 GPa. The calculations show that the added S atom in C2S3H4 breaks part of C-H bonds in C2S2H4, makes the vibration of H atom at a lower frequency, and thus enhances the electro-phonon coupling and Tc. Our results suggest that the molar ratio of C:S lower than 1:1 in the C-S-H systems may be favorable to enhance Tc. This can be useful to figure out the structure of the C-S-H material with room temperature Tc in the recent experiment.