# Superconductivity of Pure H3S Synthesis from Elemental Sulfur and Hydrogen

## TL;DR

This study reports the first electrical resistance measurements of pure H3S synthesized from elemental sulfur and hydrogen, showing superconductivity at temperatures up to 186 K with improved crystallinity and no sulfur impurities.

## Contribution

It provides the first direct measurement of superconductivity in pure H3S synthesized from elemental sulfur and hydrogen, confirming high-temperature superconductivity without hydrogen deficiency.

## Key findings

- Superconducting transition observed at 200 K
- Highest T off-set of 186 K achieved
- Synthesized H3S has improved crystallinity and purity

## Abstract

Superconductive H3S synthesized from H2S is very poorly crystallized, and has excess sulfur as impurity (3H2S -> 2H3S + S). The phase transition process undergoes in sulfur excess condition, which might cause hydrogen deficiency. The influence of hydrogen deficiency is not clear. Therefore investigation on the superconductivity in H3S with no hydrogen deficiency is demanded. Two groups performed synthesis of H3S from elemental sulfur and hydrogen (direct synthesis) and their results have shown that no hydrogen deficiency is caused when the direct synthesis is performed under hydrogen excessive condition. However, no measurements of superconductivity has been carried out because of the major technical difficulties in hydrogen experiments in diamond anvil cells (DACs). Here, we report the first electrical resistance measurements in superconductive H3S synthesized from elemental sulfur and hydrogen (3H2 + 2S -> 2H3S). Our powder X-ray diffraction (PXRD) using a synchrotron X-ray revealed that synthesized H3S has much improved crystalline quality and no sulfur as reported in previous works. We observed a superconducting transition with a sharp drop of the resistance at Tonset = 200 K and we obtained the highest Toffset of 186 K in S-H system.