Unconventional superconductivity in highly-compressed unannealed sulphur hydride

Abstract

While great scientific efforts focus on the synthesis and studies of near-room-temperature (NRT) superconductors exhibited record superconducting transition temperatures (for instance, laser annealed H3S, LaH10 and YHn (n = 4, 6, 7, 9) with Tc > 200 K), unannealed low-Tc counterparts of NRT superconductors stay in the background. However, the formers are part of hydrogen-rich superconductors family and the success in understanding of NRT superconductivity depends on the study of these materials too. In this paper we analyse experimental temperature dependent upper critical field data, Bc2(T), reported by Drozdov et al. (Nature525, 73 (2015)) for unannealed highly-compressed (P = 155 GPa) sulphur hydride with Tc = 46 K and show that this material is unconventional superconductor which exhibits the ratio of Tc to the Fermi temperature, TF, in the range of 0.02 ≤ Tc/TF ≤ 0.05.