Comparison of highly-compressed C2/m-SnH₁₂ superhydride with conventional superconductors

Satterthwaite and Toepke (1970 Phys. Rev. Lett. 25 741) predicted high-temperature superconductivity in hydrogen-rich metallic alloys, based on an idea that these compounds should exhibit high Debye frequency of the proton lattice, which boosts the superconducting transition temperature, T _c. The idea has got full confirmation more than four decades later when Drozdov et al (2015 Nature 525 73) experimentally discovered near-room-temperature superconductivity in highly-compressed sulphur superhydride, H₃S. To date, more than a dozen of high-temperature hydrogen-rich superconducting phases in Ba–H, Pr–H, P–H, Pt–H, Ce–H, Th–H, S–H, Y–H, La–H, and (La, Y)–H systems have been synthesized and, recently, Hong et al (2021 arXiv:2101.02846) reported on the discovery of C2/m-SnH₁₂ phase with superconducting transition temperature of T _c ∼ 70 K. Here we analyse the magnetoresistance data, R(T, B), of C2/m-SnH₁₂ phase and report that this superhydride exhibits the ground state superconducting gap of Δ(0) = 9.2 ± 0.5 meV, the ratio of 2Δ(0)/k _B T _c = 3.3 ± 0.2, and 0.010 < T _c/T _F < 0.014 (where T _F is the Fermi temperature) and, thus, C2/m-SnH₁₂ falls into unconventional superconductors band in the Uemura plot. (paper)