Classifying superconductivity in compressed H 3 S

Abstract

The discovery of high-temperature superconductivity in compressed H3S by Drozdov and co-workers [A. Drozdov et al., Nature 525 (2015) 73] 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., Phys. Rev. Lett. 122 (2019) 027001] 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. https://doi.org/10.2172/1481108] by utilizing four different models of Bc2(T). As the result, we find that the ratio of superconducting energy gap, (0), to the Fermi energy, F, in all considered scenarios is 0.03 < (0)/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 are located. © 2019 World Scientific Publishing Company.