The electron-phonon coupling constant, Fermi temperature and unconventional superconductivity in the carbonaceous sulfur hydride 190 K superconductor
E F Talantsev
Abstract
Abstract Recently, Snider et al (2020 Nature 586 373) reported on the observation of superconductivity in highly compressed carbonaceous sulfur hydride, H x (S,C) y . The highest critical temperature in H x (S,C) y exceeds the previous record of T c = 280 K by 5 K, as reported by Somayazulu et al (2019 Phys. Rev. Lett. 122 027001) for highly compressed LaH 10 . In this paper, we analyze experimental temperature-dependent magnetoresistance data, R ( T,B ), reported by Snider et al . The analysis shows that H x (S,C) y compound exhibited T c = 190 K ( P = 210 GPa), has the electron–phonon coupling constant λ e−ph = 2.0 and the ratio of critical temperature, T c , to the Fermi temperature, T F , in the range of 0.011 ⩽ T c / T F ⩽ 0.018. These deduced values are very close to the ones reported for H 3 S at P = 155–165 GPa (Drozdov et al 2015 Nature 525 73). This means that in all considered scenarios the carbonaceous sulfur hydride 190 K superconductor falls into the unconventional superconductor band in the Uemura plot, where all other highly compressed super-hydride/deuterides are located. It should be noted that our analysis shows that all raw R ( T,B ) data sets for H x (S,C) y samples, for which Snider et al (2020 Nature 586 373) reported T c > 200 K, cannot be characterized as reliable data sources. Thus, independent experimental confirmation/disproof for high- T c values in the carbonaceous sulfur hydride are required.