Clean-limit superconductivity in Im-3m H3S synthesized from sulfur and hydrogen donor ammonia borane

TL;DR

This study reports the synthesis of cubic Im-3m H3S from sulfur and ammonia borane under high pressure, confirming its superconductivity at 197 K and analyzing its clean-limit behavior and unusual transition broadening.

Contribution

First detailed synthesis and characterization of high-pressure H3S from ammonia borane, revealing its clean-limit superconductivity at 197 K.

Findings

Superconductivity at Tc = 197 K confirmed in H3S

H3S exhibits clean-limit superconducting behavior

Unusual linear temperature-over-field scaling observed

Abstract

We present detailed studies of the superconductivity in high-pressure H3S. X-ray diffraction measurements show that cubic Im-3m H3S was synthesized from elemental sulfur and hydrogen donor ammonia borane (NH3BH3). Our electrical transport measurements confirm superconductivity with a transition temperature Tc = 197 K at 153 GPa. From the analysis of both the normal state resistivity and the slope of the critical field, we conclude that the superconductivity is described by clean-limit behaviour. A significant broadening of the resistive transition in finite magnetic field is found, as expected for superconductors. We identify a linear temperature-over-field scaling of the resistance at the superconducting transition which is not described by existing theories.