Classifying superconductivity in compressed H3S

TL;DR

This paper analyzes the superconducting properties of compressed H3S using experimental data and models, revealing its unconventional nature and placing it among other unconventional superconductors based on key ratios.

Contribution

It applies four models to experimental Bc2(T) data of H3S, providing insights into its unconventional superconductivity and ratios of energy gap to Fermi energy.

Findings

H3S has a superconducting gap to Fermi energy ratio between 0.03 and 0.07.

The Tc to Fermi temperature ratio ranges from 0.012 to 0.039.

H3S aligns with the trend of unconventional superconductors in Tc versus TF plot.

Abstract

The discovery of high-temperature superconductivity in compressed H3S by Drozdov and co-workers (A. Drozdov, et. al., Nature 525, 73 (2015)) heralded a new era in superconductivity. To date, the record transition temperature of Tc = 260 K stands with another hydrogen-rich compound, LaH10 (M. Somayazulu, et. al., arXiv:1808.07695) which becomes superconducting at pressure of P = 190 GPa. Despite very intensive first-principle theoretical studies of hydrogen-rich compounds compressed to megabar level pressure, there is a very limited experimental dataset available for such materials. In this paper, we analyze the upper critical field, Bc2(T), data of highly compressed H3S reported by Mozaffari and co-workers (S. Mozaffari, et. al., LA-UR-18-30460, DOI: 10.2172/1481108) by utilizing four different models of Bc2(T). In result, we find that the ratio of superconducting energy gap, {\Delta}(0), to the Fermi energy, {\epsilon}F, in all considered scenarios is 0.03 < {\Delta}(0)/{\epsilon}F < 0.07, with respective ratio of Tc to the Fermi temperature, TF, 0.012 < Tc/TF < 0.039. These characterize H3S as unconventional superconductor and places it on the same trend line in Tc versus TF plot, where all unconventional superconductors located.