Absence of conventional room temperature superconductivity at high pressure in carbon doped H$_3$S

TL;DR

This study critically examines the claim of room temperature superconductivity in carbon-doped H$_3$S under high pressure, using theoretical tools to challenge the validity of such claims and suggesting potential new mechanisms or theory breakdowns.

Contribution

The paper provides a detailed theoretical analysis that questions the existence of conventional high-temperature superconductivity in carbon-doped H$_3$S, highlighting inconsistencies with recent experimental claims.

Findings

No dominant low-enthalpy stoichiometry or crystal structure in phase diagram.

C-doping phases are only marginally competitive thermodynamically with H$_3$S.

Calculated transition temperatures differ by over 110 K from recent theoretical predictions.

Abstract

In this work, we show that the same theoretical tools that successfully explain other hydrides systems under pressure seem to be at odds with the recently claimed conventional room temperature superconductivity of the carbonaceous sulfur hydride. We support our conclusions with I) the absence of a dominant low-enthalpy stoichiometry and crystal structure in the ternary phase diagram. II) Only the thermodynamics of C-doping phases appears to be marginally competing in enthalpy against H$_3$S. III) Accurate results of the transition temperature given by ab initio Migdal-Eliashberg calculations differ by more than 110 K to recently theoretical claims explaining the high-temperature superconductivity in carbonaceous-hydrogen sulfide. A novel mechanism of superconductivity or a breakdown of current theories in this system is possibly behind the disagreement.